I’m trying to figure out what’s going on with this Motorola I’m obviously missing something here bright up 14kv bright down 20 kv with little to no difference by turning the hv pot. B+ is 375 and sams says 385 I tried cap off reg tube no difference all caps at the oscillator changed and no smell of leaking hv. I have a new flyback but don’t want to change it until I go over everything that I may be missing. Another oscillator tube nothing makes a difference. If anyone has even a clue I’m all ears. I don’t have a scope which would probably help I also checked the ohms of the horizontal hold coil which sets the frequency and the hold and ohms are good.

Off frequency? Bad voltages to Output tube? Are you getting a picture that locks?

what CRT is in the Motorola ts907?

there is very little info out there on this set out there.

Also, why start a 2nd thread? you already have a topic about this set under the fried focus resistor.

Would it not all be easier to follow if it were all centralized under the same one? :D

Off frequency? Bad voltages to Output tube? Are you getting a picture that locks?

Sound but no picture full screen missing edges both sides due to low hv

what CRT is in the Motorola ts907?

there is very little info out there on this set out there.

Also, why start a 2nd thread? you already have a topic about this set under the fried focus resistor.

Would it not all be easier to follow if it were all centralized under the same one? :D

This set has the 21fjp22 and I started another thread because the focus coil resistor I don’t think has anything to do with this hv issue

This set has the 21fjp22 and I started another thread because the focus coil resistor I don’t think has anything to do with this hv issue

they could very well be related to each other, as they are both in the same section, and tied closely together to the function of the HOT & FBT.

Had a weird they happen twice I was disconnecting everything to take the chassis out and touching plugs to unplug with one hand and my arm was lightly setting on the hv cage and I was getting lightly zapped from the voltage in the crt now that would be impossible but until I removed the anode wire from the crt I was good to go. This makes no sense because the anode is in the hv cup with the 3at2 tube so how can this voltage make it to ground I have no clue. And there is a ground for the crt and that was good.

Remember, the crazy thing is all one big tuned circuit! :)

From one end to the other, it's amazing how they got it all working so well, but, it DOES mean it's easy to upset the balance, get one key element out of wack, be it the horizontal frequency, something in the damper area, yoke or convergence area, basically ANYTHING that can mess up resonant frequency of the circuit, then you have a big headache on your hands, and like I mentioned, it may very well include the focus circuit. :(

On a bk tube tester and recapped I tested the hv rectifier and it’s new but on the scale it tested on the end of the yellow bar which is around 62 on the scale I would think it’s no good but I don’t know how low it has to test befor seeing a hv problem so I tested the old one the tv came with and reads almost 90 on the scale. I didn’t try it yet but how low can this tube test befor it’s a problem.

On a bk tube tester and recapped I tested the hv rectifier and it’s new but on the scale it tested on the end of the yellow bar which is around 62 on the scale I would think it’s no good but I don’t know how low it has to test befor seeing a hv problem so I tested the old one the tv came with and reads almost 90 on the scale. I didn’t try it yet but how low can this tube test befor it’s a problem.

Unfortunately, as is often the case with tube testers, especially with the power type tubes, they never give the full story about good/bad because they can't put them in real life load situations that they would be in the circuits they are being used in, in these cases, it's always best to try a "known good" one.

cause they often fool you.

WAY TOO MUCH info on tube testers, but it shows what you gotta deal with. :yes:

http://www.tungsol.com/html/faqs7.html

I don’t know if these series chassis were known back in the day for flyback failures the last Motorola I had I changed the flyback so with this one I have a new flyback and I put it in so I’ll see what happens. I keep going over this chassis and every cap I changed tested new and every resistor I checked tests new as well so if I still have low hv then maybe the yoke. I’m not sure really how to check the yoke coils ohms. I changed the rectifier tube and gained 4 kv but just won’t adjust via the hv pot it will lower from where it is but that’s it.

Boost voltage off the flyback is around 750 volts should be 770 volts after a 10k resistor and b+ is 350volts and should be 385 volts. I don’t know if the b+ diodes go weak from age has anyone had these diodes go weak by not putting out the correct voltage and if b+ is low everything else will be low. And the line voltage is 111 volts. Originally the b+ was 375 volts I don’t know why it dropped.

If the boost diodes are selenium (possible) I’d be looking there.

B+ diodes no boost diodes in this set.

B+ rectifiers almost always DEAD SHORT
B+ 375 vs 385 not a problem. Only 3% difference.
Boost low probably due to low HV. Boost is added ON TOP of the high B+.
Comes from FBT pulse then filtered & sometimes rectified.
Boost feeds the CRT G-2 controls & often the Vert & Audio.
If you pull the plate cap OFF the HV rect tube you should be able to draw a nice
1" arc into the air. If you can things are probably good to there.
Pay attn to the hoz out voltages. The G-1 HAS to be very negative per
the manual.
73 Zeno:smoke:
LFOD !

Well that 375 volts I posted now dropped to I think was 350 volts the b+ diodes are not shorted but one side of the diodes is only 179 volts that comes to 358 volts it’s to low and all the big resistors for b+ test like new so with having low hv I would think it because of the low b+ and the reg tube cap off does nothing the hv should jump to like 30 kv and I had a new flyback that I put in and that made no difference. I’m kind of lost at this point. The g2 settings red low blue and green about half.

Ok so this is baffling chassis out on the bench nothing plugged into it except line cord to check b+ transformer putting out 143 vac just what’s listed in sams checked diodes they are good diodes in circuit no load goes up to 358 after 30 seconds voltage drops to 340 there should be 385 or 390 volts cannot figure why it’s so low I thought maybe I got a bad cap even though I checked them befor using them and checked good.

Bad cap about only thing left with PS unloaded. Be sure the choke
isnt shorted either.
You can bridge them to test.
Take about a 50mfd 450 volt and hang it right on the old one
+ to + , - to - see if any improve it.
As you try different sections DISCHARGE it between.
Get in the habit of that cause if you do a SS set you can charge up 150 volts then dump it on the 24 V line, not good.
This was a "fix TV 101" subject. Also for radio. Best use was quickly get the
TV going to evaluate for est.

Zeno

Do you mean the chokes on the ac input there are 2 I don’t think there is a choke on the dc line. I have only 2 caps that are responsible for the b+ voltage they are both 250 v 160 uf one cap tests 175 uf the other tests 202 uf so I don’t know if that indicates the cap is bad.

Ok so piggy backed a 470 uf 450 volt cap and it jumped up to 390 volts and it backed down then started rising up having to allow 30-40 seconds for the thermistor to heat up. New caps are bad.

This set has 2 250 volt 160 uf caps wired in series so that means it only gets 160 uf but if parallel then it would be 320 uf somehow it don’t make much sense to do this it’s like having and extra cap for really no purpose if it’s only 160 uf why not just have the one cap.

This set has 2 250 volt 160 uf caps wired in series so that means it only gets 160 uf but if parallel then it would be 320 uf somehow it don’t make much sense to do this it’s like having and extra cap for really no purpose if it’s only 160 uf why not just have the one cap.

Are you referring to C1 & C2? I can't see the schematics very clearly cause the ones given are so low res, but if so, they make up a voltage doubler circuit, and are thus critical to get the correct bias voltage.
In such situations, it never hurts to go slightly over like 180uf or so.

example, a pair of these should last forever!
647-UCY2D181MHD3
It's what i would use. :yes:

Ok yes it does make sense voltage doubler and yes c1 and c2. Well I have 2 more caps coming and if the voltage is not up to where it should be then it may be time to replace the diodes with 1n4007 diodes.

The doubler cap thats above GND needs to be same temp rating or
higher. They take a beating.

Not sure what you mean by the cap above gnd

It's pretty much a standard that both caps in a voltage doubler should be of the same size and type, and for best results, 2 an exact pair is best.

Does anyone know if the b+ diodes are supposed to get warm with the power supply unloaded.

Does anyone know if the b+ diodes are supposed to get warm with the power supply unloaded.

define "unloaded"

how did you unload it, and if it's truly unloaded, with the sec - > diodes -> caps, it could lead to a runaway condition where the bias voltage goes over the rating of the caps.

Chassis on off switch jumped on the bench no tuner no hv hot caps off no convergence none of this is plugged into the chassis. Best way I can define unloaded. I checked the voltage on the b+ line no run away voltage I had new caps that seem to be bad 2 more caps seem to fix the low b+ I had.

The only TRUE way to insure that it's really unloaded is to unhook one side of the choak (L54?), that will make certain that there is no slight draw anyplace, but there is most likely no real reason to do so, it's rather normal for those diodes to get a bit warm under normal operation.

2 new old stock tubes for video IF both don’t even read on the tester I still have low hv I don’t think these 2 tubes have anything to do with hv. If I turn the horizontal frequency which is also the horizontal hold in about 5 turns the screen fills and I get good hv but the slug is halfway out of the coil not sure that is correct. I’m lost at this point.

If you have to back it that far out, there is clearly a problem with the horizontal oscillator/AFC , this can include the phasing det and feedback loop ( winding on FBT), SOMETHING is causing it to be way off frequency. :(

If you have a good digital o-scope, it may be a good time to see what your horizontal frequency really is right now.

No don’t have a scope. The flyback is new I put that in and are you talking about the chroma phase detect with the 6al5 tube. And all the caps were replaced and every resistor around the horizontal oscillator was perfect if only I could find a possible bad resistor.

No don’t have a scope. The flyback is new I put that in and are you talking about the chroma phase detect with the 6al5 tube. And all the caps were replaced and every resistor around the horizontal oscillator was perfect if only I could find a possible bad resistor.

I'm not sure how it's done in this set exactly but the horizontal oscillator is norm always phase locked, look for telltale shark fin waveform on the schematic for the area, you are in a level of complexity now that w/o a oscilloscope you are basically working with your hands tied and one eye shut, you really need to get one to track down problems such as this, they are that complex.

One thought I had was one of the 3 caps in the yoke may be bad I can check NF but not PF so I’m not sure and there are 2 560 mmf 2.5 kv ceramic disk caps on the horizontal side of the yoke.

2 new old stock tubes for video IF both don’t even read on the tester I still have low hv I don’t think these 2 tubes have anything to do with hv. If I turn the horizontal frequency which is also the horizontal hold in about 5 turns the screen fills and I get good hv but the slug is halfway out of the coil not sure that is correct. I’m lost at this point.

Keep it painless first. Change hoz osc tube ( 6BL8 ? ) first.
If slug is way out but HV OK the hoz osc is way off the norm. Recheck caps
& VALUES used. In theory at this point the sweep is giving full width & HV
Try hooking up a source & look for clues. Hoz AFC can be defeated by grounding it out at the right point & will give a "floating" pix. I dont
have schematic so cant say exactly where. Never seen H AFC or the feedback from the FBT cause this prob. BUT ??

BTW if this set uses 6BL8's or 8BL8's just swap them out to test.
It was Motos 6GH8 but a better tube.

73 Zeno:smoke:
LFOD !

Horizontal drive circuit

Already swapped tubes no difference at all and every component within the horizontal oscillator circuit was either changed or checked but ceramic disc caps certain ones I cannot check. Discs are reliable but do go bad.

How much hv should be present at the anode without crt and yoke in circuit.

How much hv should be present at the anode without crt and yoke in circuit.

No telling what the answer is without the yoke in circuit. It is a vital part of generating the high voltage.

So if I plug in the yoke for hv testing but not the crt it should generate the proper hv long as all is good I know the crt acts like a capacitor but will it generate full hv without the capacitance of the crt. Chassis on the bench and these motorolas are different and I don’t have the pin out for testing on top of chassis at lots of test points.

No telling what the answer is without the yoke in circuit. It is a vital part of generating the high voltage.

Exactly!

It's all part of the tuned circuit mentioned before, a big feedback loop, I kinda think they made it that way to protect the CRT if something were to fail, if the horz sweep was not right, the HV would shut down and protect the face of the tube from burn.

Does set still have 2 hoz out tubes ?
It would be interesting to see if they are drawing the same cathode current.
OK on discs. Almost all I changed were burning or cracking open or dead
shorted. BUT ?? If you try them I would nip one end then hang in.
Maybe someone still sells an assortment, I would go with 1KV ones.
BTW its getting long so what is the voltage on the G-1's of the
hoz outs ?

Zeno

Ok here’s the kicker the voltages we’re pretty close after checking yet more resistors still finding not a thing wrong switching tubes checking hv pot 6bk4 cap off still lousy hv until I have a light above the chassis I turned off to make sure the heaters were all lit and what do I find but one of the HO tubes top glowing blue lucky I had a good used one put it in reg tube cap off and a massive hiss and lots of corona and I did plug in the yoke on the bench. These 2 tubes were brand new but yet one was bad so I’m sure it’s going to be ok now I’ll find out Monday when I get 2 6eh7 tubes for the IF again new but we’re bad.

Ok here’s the kicker the voltages we’re pretty close after checking yet more resistors still finding not a thing wrong switching tubes checking hv pot 6bk4 cap off still lousy hv until I have a light above the chassis I turned off to make sure the heaters were all lit and what do I find but one of the HO tubes top glowing blue lucky I had a good used one put it in reg tube cap off and a massive hiss and lots of corona and I did plug in the yoke on the bench. These 2 tubes were brand new but yet one was bad so I’m sure it’s going to be ok now I’ll find out Monday when I get 2 6eh7 tubes for the IF again new but we’re bad.

When you get NOS tubes beware that many came off a shops shelf
& may be damaged ESPECIALLY hoz outs & big audio outs.
Best to stick with RCA, GE, & Sylvania. Tubes from set mfrs like
Zenith Moto, Maggy etc are a safe bet, most are made by the big 3.
Lots to NOT by, Lyndal & IEC are two junker tube lines.
Well done, progress made !

Zeno:smoke:

One thing to check for is that your CRT G2/screens aren't set too high...I have an industrial Setchell Carlson monitor that for more than a year I couldn't figure out why focus was terrible and HV was very low, but it was fairly bright....The CRT was good and strong and someone had one of the G2s set near max and it was literally making the gun conduct so HEAVILY that the CRT was literally overloading and lugging down the HV. I turned down the G2 and suddenly it was working really good and HV and focus were where they should be...It's not a common issue but it's something to be aware of.

Yes Tom early on I lowered the drives and the g2 pots.

Well at it again got perfect hv now but now I have good sound but no picture no video just a blank screen little fuzz checked tubes again even the tuner tubes. There is the 1n60 diode I don’t know if that affects video and sound or just video other then that any ideas from here maybe something obvious that again I’m missing.

Again, this is a situation where having an oscilloscope would be extremely helpful.
If sound is good, then tuner & IF up to #3 are most likely OK, as the sound is taken off the 3rd video IF V3. So the problem should be after that in L6 and after, the video detector may be faulty, or any one of those peaking coils between L6 & V4 P7.
If you did have a oscilloscope, the method would be to check for the 5v PTP video, starting from the anode of x6, and trace it down to V4 P7 to check it has a clear path.

But w/o one, it's much harder, check everything starting with x6 → V4 P7.

Can a 1n34 be used in place of the 1n60. P7 ?

Can a 1n34 be used in place of the 1n60. P7 ?

As far as I can tell, the 1n34 is also a Germanium that's often used for TV video detectors, and as far as I know, they really are not that picky as long as you stick with the general type of diode.

Thanks but what’s the p7 you refer to

Thanks but what’s the p7 you refer to

I'm looking at the SAMS for the set, P7 = pin7 of V4 video amp 6AW8A, should have a 5v PtP video there.

The voltages are somewhat low because the chassis is out and no tuner plugged in. I had picked up lindal tubes and they say they are no good so I have 2 more coming so maybe these tubes are no good since I had 2 others that didn’t move the needle on the tester and yet I had sound. X6 is almost impossible to reach but I did a test these Germanium diodes are so sensitive that testing each end causes the numbers on the meter to jump back and forth and that’s what the diode in the set did exactly with the diode I have in hand did the same so I’m assuming it’s good and from one end of the diode to pin 7 has continuity. Voltages on 6w8a are there but 7 I think was not 5 volts more like 12 volts but no tuner plugged in.the other part to this is channel 3 may be way off as far as tuned don’t know the history so took out the tuner and the slug for channel 3 was all the way in I don’t know if it’s usually in or out more then in so I ran it out and sprayed the gears the grease gummed up wasn’t really working now it is so I’ll find out tomorrow what happens.

One thing you can do as a diagnostic is to inject composite video at the output of the video detector if you get video on screen then the problem is between the tuner and detector, if not then the problem is in the video amp...This is a good way of eliminating half the video path from suspicion.

If you have tuner/IF issues and you another set with a modern 44MHz IF or a Blonder Tongue AM series agile modulator with an IF out port you could connect either of those in place of the sets original tuner and check if you get picture...If you do then troubleshoot the tuner in the set, if you don't troubleshoot the IF and AGC systems.

Well I’m putting my hopes on the tuner channel 3 is way out of where it should be to get a picture I do have sound but it was fading in and out.

if you are getting sound trough, you should be seeing SOMETHING on the screen, some kind of noise pattern, herringbone pattern, something getting through, as mentioned, the signal is getting as far as 3rd IF, even if it's distorted, you should se something on the screen.

and Electronic M has a valid idea, but be sure to put it through a isolation cap, like a .01 or something like that, so you don't fry your video source.

it needs 5v PtP, but you should see a faint image with standard composite 1v

You have 2 places to try to inject video as EM suggested, it may help you a lot to try it.
http://suzaku.live-evil.org/injection-points.jpg

But as shown on the SAMS, it expects 5v pk-pk at that amp, and composite is only just about 1v, but you should see something.

There is also that 13v potential to deal with, so be sure to feed through an appropriate film cap .01 (guess).

I have done this myself many times with good results.

I do get alittle snow and some lines on top of the screen but to inject a signal would be kind of Impossible hectic access these Motorolas have test points on top of the chassis but the sams don’t show what they are for testing what.

I do get alittle snow and some lines on top of the screen but to inject a signal would be kind of Impossible hectic access these Motorolas have test points on top of the chassis but the sams don’t show what they are for testing what.

I literally soldered on a lead of a cap to pin 7 of the first video amp on my RCA CTC-16XL when I was working on it to feed in video.

When a point is hard to reach with the chassis installed I pull the chassis enough to reach it, hook an alligator clip lead up to it to bring it out to an easy to reach point and use that.

If you happen to have a working TV test pattern generator with variable output most of those were designed to give 5V or more output to give a nice contrasty output.

Test point B is quite easy to reach from the top of the chassis, and clearly pointed out in the SAMS, you can clip there for video input.

Where on the schematic is test point B on top of chassis would that be to pin 7 of 6aw8

Where on the schematic is test point B on top of chassis would that be to pin 7 of 6aw8

pint b is here

http://suzaku.live-evil.org/poin-b.jpg

its between l10 and l11

http://suzaku.live-evil.org/injection-points.jpg

i have be using this, which i assume is correct?

https://www.earlytelevision.org/pdf/motorola_ts-907_sams_739-3.pdf

Oh obviously I’m missing that page that shows point B. Yes you have the correct schematic.

Ok so on channel 4 I can almost tune in a picture but can’t make anything out of it and it looks like the horizontal hold needs to be adjusted i tried but won’t clear up so I don’t know if the sync section can keep a picture from displaying along with the h hold not being able to adjust out. I ran the slug all the way in to all the way out.it’s clearly trying to tune in since I got the tuner working properly but just won’t tune in and sometimes on 3 the sound fades like it’s out of tune so the video is getting to where it should. Just when I think the pic is going tune in it don’t it’s that close.

This of course points right back to the low HV area problem.
For some reason, the circuit is not able to synchronize to the incoming video input, this could be for many reasons.

SYNC SEP, SYNC AMP, HORZ AFC, HORZ OSC , & all associated circuits are suspect.


I hate to keep repeating it, but it's the way it is, w/o an oscilloscope to check that you are getting the right signals at the right points in the circuits, you are making this exponentially harder for yourself than it needs to be.

Well yes I know a scope would be a big help and yes it’s frustrating seeking problems without it but as for the hv as I mentioned in an earlier post the problem was a bad ho tube and I even checked ohms on the horizontal hold coil which checked out perfect. And those circuits you mention all new caps and endless resistors checked perfect. This set is beginning to give me a headache lol. Even tubes keep checking them. Those metal shield’s in the IF section is it important to replace 3 solder connections to ground even though there are screw’s holding the shield in place to ground.

So is it safe to say that if you have sound then the video is there as well. I know audio goes one way and video goes in another direction I’m trying to rule out the tuner the slugs do move, I since got those gears to move freely.

Video and sound typically stay combined until the output of the video detector. If you have sound the tuner and IF are not dead...God only knows if fine tuning, IF and audio alignment are correct, or if your video amplifier works at all.

Without a scope or a means of/will to do signal injection such as the procedure I discussed earlier you're basically flying blind without instruments.

There comes a time where the value of the time you waste trying to make do with insufficient test gear is worth so many times the cost of a working used $50 1970s or newer scope, B&K analyst, etc that NOT buying one is costing you much more than buying one.

Watch “that auction site”. You can find even a recent Tektronix for cheap, and that’s all the scope you need to get up and running in scope land. When you see what a scope can do for you, you wonder why you didn’t get one sooner….

Well I have been in the video amp but I didn’t check the video output maybe something there would cause this video issue. How about the blanking circuit ?

Ok well low voltages can give all kinds of problems things won’t work so at 113 volts ac b+ is 360v and the source voltages are 275 is 251 v 190 is 131 v 145 is 175 v and if the 2 voltages were swapped they would be functional and my problems would probably be solved and yet I went over my work with the power supply caps and appears right so this does look like I have 2 power supply caps reversed. I did this with chassis out horizontal tube caps off no hv but these source voltages I would think should be up to par without hv because it’s a source voltage.

Hi Timmy, I believe you have a Power Supply Problem.
You may even have multiple problems, but you need to
focus on the power supply if the below voltages are
actually what you are reading. Check this stuff
in this order.

385V Source - Your reading 360V - too low.
275V Source - Your reading 251V - Too Low.
190V Source - Your reading 131V - Too Low.
145V Source - Your reading 175V - Too High.

So lets figure out what's going on with the 385V. source. First off I assume you
already changed all the power supply caps, So be sure they are the correct values,
and correct voltage ratings, and in the correct spots.

If you do not have 395V at Doide X2 you should then check for 143V AC at the output
of the power transformer that feeds the Voltage Doubler circuit. If it's LOW
than you need to check the Thermister R211 to be sure it's ok.
You can check the other do-dads on that side too, be sure nothing
has an excessive voltage drop across it, Switch too.
Be sure the circuit breaker does not have high resistance across it.
L54 should be around 12 ohms. Be sure to check that W, Z Stuff at the
lower winding on the power thansformer. That 275V source goes through
a few caps & goes to those HV Reg Filiments. You remember having
a Short in that circuit on another tv you worked on with Low HV.

If Ok;

At L4 the choke in the power supply, there is a current reading there of 380ma.
You should use your current meter to be sure this is at 380, if high there is a
excessive current draw. If low you have something open possibly.
Be sure to cut, or remove the input line to the choke, put your current meter
in series with the choke & Diode, use a high current scale, Like 10A, because
the resistance of the current meter will be very low, like 1/10 Ohm, and will
not cause a voltage drop across it.

The 385V source flows through a 550 Ohm resistor R214 and becomes the 275V
Source, you should check this resistor.

Also check R 215.

Finally, Your 145V source is too high...... Please check R 216. And be sure to check all
your wiring in this step.

For your 145V Source to be too high, there is either a wiring mistake, or a possible
shorted capacitor between two voltage sources that can possibly be bringing some
higher voltage to the 145V source. This can be anywhere in the tv.

Next step is - you can see below the power supply is a small box that tells you
exactly how many connection points each source goes to, You will need to start
checking these.

The box is called B+ Distribution

If you read more that 380ma. then you need to disconnect each of the 9 - 385V
sources and try and see if one has a high current draw. Disconnect one, turn the set
on and check 385V source. If it goes up, that point can have a problem.

You need to do this stuff with everything hooked up & ready to work as usual.
You can't do Power supply stuff with parts of the tv turned off, or disconnected.

Good Luck I Won't be around much this week......

..

.

Yes most of what you mention I already checked the choke 11 ohms a new thermistor all the power supply caps even checked them parallel them I even checked the sams for where the 275 190 and 145 voltages go and traced them back to what I did in the power supply, checks fine. At the diodes it’s the same 360v the doubler caps have 180v on each cap diodes clipped there is 143v ac present thermistor is new the 550ohm resistor checks perfect all the ps caps are exact or higher in capacitance. I’m going to check line voltage going to the primary of the power transformer tomorrow and hopefully rule out a thermistor problem or transformer primary problem. And also the 15k and 5.6k both are perfect. All this is with 114v or so line voltage.

Be sure also to double check the polarity of C1 & C2, See how they are hooked
up in the circuit. The 2 160Mfg Caps in the Doubler Circuit.
And check the 380ma current.


.

Polarity is good I went over that several times along with everything else double checking. My digital meter can check amps not sure of ma or if I can get it on the wire. C1 don’t go to ground iirc. Well maybe I’ll pull tubes one by one maybe one is defective in such a way that it would cause a drop in voltage.

Wait a minute. Did you say a thermister was bad ?
Did you change it ?
If you did it could be the wrong type. Some go up in ohms when
hot & some go down.
Also does this use a relay for DGS ? Moto was one that did
but I dont remember how they worked. That was the early 70's
that I last changed one !

Zeno:smoke:

Wait a minute. Did you say a thermister was bad ?
Did you change it ?
If you did it could be the wrong type. Some go up in ohms when
hot & some go down.
Also does this use a relay for DGS ? Moto was one that did
but I dont remember how they worked. That was the early 70's
that I last changed one !

Zeno:smoke:
Changed the thermistor already exact one for the set moto number and no relay

Would it be a bad idea to jump the thermistor to at least see what the voltages show.the strange thing is first turn it on b+ will show 390v but steady it drops and lands at just making it to 360v.

You are most likely chasing a phantom here.

Remember that no 2 sets are exactly alike, and tubes are VERY forgiving about their bias sources.

If it says "385v" on a SAMS, this does not mean that the MUST BE that voltage there ABSOLUTE, there will always be variance, sometimes +/- 10% and this does not necessarily mean there is a problem, this is in fact normal.

but by all means, check the PWS area, but you will most likely find, there is nothing to worry about there.

:D

If you first get 385V and it drops as the set comes on, then it's possible a tube is
conducting too much current, and dragging down your 385V Source. It can be
ANY Load connected to Any Spurce point, But start with 385V.
As for the starting voltage, The formula for figuring Voltage from a doubler is
approx 2X(V-Peak) - .7V(Diode Forward Conducting Voltage.) From the
Transformer ( 143V X2 ) -.7 = 185.3V

If it's drawing more than 380ma. it is reasonable to believe a circuit may be drawing
more current than it should.

If your transformer secondary is less than 143VAC I would first go forward
and look on the primary side. The 143 V is with the tv on and all stuff
hooked up as in the schematic.

Not a Phantom, He has several PS voltages too low, and one too High.

You better double-Check that Thermister too.....

.

Would it be a bad idea to jump the thermistor to at least see what the voltages show.the strange thing is first turn it on b+ will show 390v but steady it drops and lands at just making it to 360v.

You may cause excessive current to flow. You can check the AC voltage drop
across it.

It might be a good idea to check line voltage, & Compare it to the primary
of the power transformer. I think it should be a small difference maybe
10VAC no more......??

113V at cheater cord, Maybe 108VAC at primary???? I don't know what to
say about that, I have no idea what THAT Thermister's specs are???

The Thermister at 25 Ohms cold, My Guess is it would go close to
Zero when it warms up, So Very little voltage drop across it.
when it's hot....

L46, & L47 appear to be line filters, There appears to be no Degaussing
circuit on the schematic. The Thermister must be to prevent a surge.


.

As for the thermistor I got the same results from the new thermistor as the old one. None of this make any sense to me tracing the 145v to specific tubes and trace back to the power supply and there’s 175v. It still seems to me that something is crossed within the power supply cap network so I’m going to go back to this area and look again because it make no logical sense to have 175v at a 145v spot this voltage is coming from somewhere. Bottom line is I believe something is back feeding another circuit and I need to find it. I would think if something is pulling it down then all the voltages should be bottoming out but there not the circuit has no real amperage to keep voltage up during a short of some kind.

You are jumping too far ahead of yourself, don't focus on the 145v issue yet, for that is load dependent, IE if the 2 loads on it are insufficient, it will drift up, no matter what you do.

Go through the steps that Squirrel boy described, especially the current check at L54 (380ma ).

go through the checks he gave.
AC V@ plug before L46/L47 and after.
AC V@ primary of power xformer (blk-red/black)
AC V@ secondary of power xformer (red/red-green) before & after M7, 143ac
DC V& Ma@ L54 395V 580ma.

145v is sourced via 5.6k resistor (r216) from the 275v rail, and goes to L25 & v9, as mentioned, if things are not right in other parts on the set, the load on the 2 won't be normal, and it will drift up.

The 145v seems to be primarily used for Audio, pin 8 of the audio output, and power to the Audio det/limiter, but it also goes to pin 5 of the tuner power connector to provide 130v B+#2. If the tuner is not connected/ inactive, the load on the branch for 145v won't be enough, and thus read high.

On the choke red wire measures .29 amp yellow wire nothing. Not sure what that comes out to in ma.and the thermistor in place warmed up the ac lost 2 volts ended up at 113 vac so not bad I have an ac running here on the same line so it will be alittle low. I think I’ll run 3 wires out for the 3 voltages 145 190 275 to check with the chassis in all hooked up and take it from there but I do know the b+ was always low hooked up or out on the bench.

.29a = 290mA

very odd, could the DVM have been set for AC amps rather than DC?

My dvm has both ac dc but it showed up on the ac scale not the dc. Is 290 ma not so good thing here.

it needs to be on the DC scale in order to take the correct measurement shown on the SAMS, if set to AC, it can be triggered by the AC ripple and give an inaccurate reading, thus you got .29a on one side of the coil and nothing on the other when set to ac.

My dvm does it digitally no way to set it to dc. Maybe the diodes are leaky at this point I don’t know.I checked my dvm I can switch it , it’s got ac on top dc on bottom micro amps if I switch it it goes to ac micro amps so I had it set right.

My dvm does it digitally no way to set it to dc. Maybe the diodes are leaky at this point I don’t know.

Time for a cheap DVM that will.

I have one of these as one of my 3 " throw away" DVMs

https://www.amazon.com/gp/product/B07DW681FQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

If i fry it, no big loss, and I CAN set it to DC amps.

Maybe there’s to much ac here idk. Diodes come to mind.

SI diodes don't normally wear out, this does not mean they can't be damaged or stressed, but if used within specs, they tend to last forever, unlike selenium.

I just find VERY unusual that you can't set your DVM from AC/DC amp measurement modes, if this indeed true, it casts doubt on everything it's telling you, and I do wonder what the heck type that is, cause in all my many years of tech repair, I have never seen that before.
And, it's highly recommended that you get another DVM, like the one I suggested, or any other low to mid range one, and use it as a 2nd opinion.
Don't rely on just the one, especially if it WON'T let you put it into DC amp mode.

Well this dvm never failed me it’s a g2 phoenix it just didn’t pick up dc I don’t know why. it has 2 scales top and bottom ac top dc bottom and when I powered up with the clamp on it initially gave me a quick number on the dc scale but went right to ac. I’m going to put the chassis back in and check the 3 voltages. I have 3 wires coming out to check these voltages.

That explains it...
The inductive clamp sensor can only mesure AC current.
To test DC, you must put the meter in series with the filter.
http://www.instrumart.com/assets/uei-g2-phoenix-manual.pdf

WARNING

your DVM can only take 2a max.

https://www.youtube.com/watch?v=x2NLYydxbo4

You must put the DVM in line between the output of the diodes and the filter.
The clamp on thing won't work.

Oh ok so much for that lol.

Ok chassis back in hooked up b+ 350 v the 145 v is now 133 v the 190 v 165 v the 275 v is 244v these voltages are more in line now but drastically low and this was at 114 vac. I guess I’m going to pull tubes one by one maybe there’s one that was manufactured wrong even though the heater works all tubes do light up heaters are good. Well I hope it do come to a shorted ceramic disc finding that can be challenging unless a short goes away when a tube in that area is pulled.

Keep in mind, the SAMS had the voltages taken with an input of 117, if you ar running at 114, you will of course see lower voltages, HOW MUCH lower, who knows.

to be 100% sure, you should be on a variac and at 117v AC input at least input, just like the SAMS says.

this 3v may seem like not very much, but once it gets through the doubler + the RMS of everything, who knows.

Maybe so but I still at one point I had 120 v and still had the low voltage.

You still have yet to determine what the Ma load is at the point between the connection of x2/c1 – L54, as mentioned, you will have to put your amp meter in series to see if you have excessive load , more than 580 ma,
and as been mentioned by others, check for voltage drop across circuit breaker M7.
Check for 147vAC on the secondary.
Check for voltage drop across plug & Socket 2 ( 9 – 8 )

And if you STILL find nothing, & current is within normal, your voltage doubler could simply be under preforming with your chosen new caps.
I would still recommend larger ones 180uf @200 647-UCY2D181MHD3 and these diodes 78-SF4007
I have used this combo many times w/o any problems.

I already changed the doubler caps to 250 v 180 uf both the same. I checked ac line in at the thermistor with a loss of only 2 volts. I was thinking of replacing the diodes with 1n4007 if I have to. I also had checked for any resistance with the breaker and I also disconnected the diodes and the secondary has 143 vac just what the sams shows. And I don’t want to burn my dvm but I remember I have a ma meter I used to used for cathode current on the rca clones.

One thing bothers me. Go back to @1975 with this set. It comes in
no snd / no raster. Something finally killed it No mater how many
other problems it has, probably many, one thing should bring it back
to just running.
After a quick check to see if the PS is up & running go to the H sweep, maybe
the H out tube is dead. We did not pull a Sams to be sure the voltages were
within 3%. At that point the jug was evaluated ( by eye) & it went from
there. SO IMHO only get the raster back & not worry so much about the
crazy PS voltages. You only need a few voltages to make the H osc & H out run even with lowish B+. You may have bad width but it will give you a raster.

BTW Never blindly trust Sams or the OEM manual !
BTW #2 A good meter is a lifetime investment. Since the 70's I have
had a Hickock ( bench meter) a Beckman & a few flukes. They all still run
& are very hard to accadently get fried. I also got both my sons Flukes
for xmas.
BTW#3 Never blindly trust a tube or CRT checker we NEVER used a tube
checker but had a TOTL B&K for customers & it was a big profit center !

enuf fer now
Zeno:smoke:
LFOD !

Yes I Agree with Zeno, you need to invest in a good meter. I got me a brand spankin
new Beckman 330 back in the day, Love it, works like a charm. Loved it so much
I got a second a few years ago off ebay for $30. It had calibration stickers on it
from a lab of some kind. Checked it on all scales against my original, & it's Spot On!

The 2V drop across the Thermister is great! At this point you need to partly suspect
your meter on some readings. Also be aware some cheaper meters are not so immune
to AC noise on your DC readings. And DC Amps you have to use probes in series
with what your testing. Clamp is only for AC.

Also be aware that the Horiz Output tubes get a feed from your 385V source, and as
stated above, this could be dragging down your power supply voltages. There are
both Voltage & Current numbers printed on the schematic that can be helpful
in the H Output circuit.

If you have all the stuff in the PS working and have low voltages then you need to look
at excessive current draw somewhere in the set, and that can be dragging down your
voltages.....

This schematic is very smart, Most power supplies will produce it's designed voltage
At some rated Current. Once that current is exceeded the voltage begins to drop.
This is one possibility, and it's for you to find.... That's why there are current readings
at key points on the schematic for this tv......




.

I know there are key points to test but none are listed specifically for ma or amp or what the parameters should be.

I am also in agreement with what the others are saying, better test equipment is needed.
Especially as many have stated, an oscilloscope, or else you are in risk of just going in circles.

For example, my list of stuff includes.
Fluke 77 Series II Multimeter
Fluke 117 multimeter
Tektronix 7934 oscilloscope
The above is the authority and bedrock of most all my testing.
Extra stuff is.
LCD 1999 3 1/2 BM4070 LCR Meter
LCR-T4 Mega328 Digital Multi Tester
Etekcity Digital Multimeter MSR-A600
Proster Digital Multimeter Mini Multi Tester
Crenova MS8233D Auto-Ranging Digital Multimeter.

This stuff is rather cheap and therefore I'm not afraid to damage it in any kind of risky tests, and they have held up well so far, and even though they are what I deem cheap throw away equipment, they still tend to agree with the calibrated Fluke meters over 97% of the time.

What would cause resistance in the circuit breaker it’s just an on off switch , arcing ?

What would cause resistance in the circuit breaker it’s just an on off switch , arcing ?

The circuit breaker is a common failure point, it's not just an on off switch, it has a thermal element that reacts to current, and causes the breaker to trip when it goes over set point.

carbon on the contacts is the reason for most fails.
If you are seeing large voltage drop across it, then it's clearly bad, you can temp jumper it to see if the voltage problem goes away.

Ok placed the ma meter plugged in started low around 80 ma but as the tubes heated the needle went up steady and quickly and it pinned my meter at 500ma the meter only goes to 500ma so I have a massive load pulling it down.

Ok placed the ma meter plugged in started low around 80 ma but as the tubes heated the needle went up steady and quickly and it pinned my meter at 500ma the meter only goes to 500ma so I have a massive load pulling it down.

SAMS says "580ma" at L54,

So it stands to reason, that once the HV kicks on and the sweeps start up, it will jump over the range of your meter of 500ma, if that's its limit.

My schematic the ma is kind of messed up can’t make out why it says ok so it says 580ma I thought it should be around 380ma. I would think 580 is absolute max

My schematic the ma is kind of messed up can’t make out why it says ok so it says 580ma I thought it should be around 380ma. I would think 580 is absolute max

not exactly, it will be different from set to set, tube to tube, don't be surprised by a difference of 10-15%

Well this ma went up very fast and I would have thought as it approached the 500ma it would have slowed down but it didn’t it was fast. My dvm only goes to 400ua so this meter can’t use

Well this ma went up very fast and I would have thought as it approached the 500ma it would have slowed down but it didn’t it was fast. My dvm only goes to 400ua so this meter can’t use

Avalanche event, horizontal oscillation starts, HV comes up and so does horizontal sweep, there is now boost for the vertical to start, voltage is now optimal at CRT for raster.
All these events in succession cause a rapid uptake in current, this is normal.

Ok makes sense but now it’s anyones guess what’s going on here. I already put in 2 sets of b+ caps the doubler caps.

Well I pulled one tube at a time voltage went up very little or went down alittle at this point this could be either not enough ac for some reason or a cap ceramic or one of the red caps but as of now at least 70% of the red caps are changed already and every one I took out checked perfect unless there’s one I didn’t change may be the bad one.

The circuit breaker as shown on the SAMS is starting to bug me A LOT.
It has to be an error.
With the secondary rated at 143v @ .58a, there is absolutely no way for it to be protected by a 4.5a circuit breaker, the transformer would self destruct long before the 4.5 breaker tripped.

I have checked the RCA CTC 10/11/15 schematics, which have basically the same type of power supplies, and they have 2.1a breakers.
https://www.ebay.com/itm/393284894216
which makes much more sense.
The SAMS listing of 4.5a has to be an error, IMOH.

No it couldn’t be protected.

Is it at all remotely possible that the diodes or one of the diodes could be compromised in some way.

If that were the case, you would likely see more drastic effects like excessive AC ripple at L54, if the diodes were not working well, or overloaded, the listed 1.5 ptp would be higher.

Double check the transformer 148vac befor diodes. I guess it’s time to start cutting wires to the specific circuits the 275 145 190 and each one cut hopefully the problem shows itself.

Double check the transformer 148vac befor diodes. I guess it’s time to start cutting wires to the specific circuits the 275 145 190 and each one cut hopefully the problem shows itself.

That will achieve very little, if anything at all.

The moment you start to deny power to areas, sooner or later you will hit something critical, and cause horizontal sweep to shut down, and thus no HV, or vertical and raster, and w/o that, the power will spike.
There is just no way around it, you need a better DVM to measure current draw to see if you do indeed have too much draw.

On breaker we used Mallorys. They had a carry & break rating.
The hoz outs alone are good for 240ma.
You can try pulling all the low level tubes & leaving in the hoz AFC, H osc,
2 hoz outs, damper, HV rect and HV reg. BTW I looked, can someone
post the PS schematic ?
Also does anyone look at an OLD Sams index & see if there are any
PCB's on this set ? I have a 2001 & for some reason none
of the TS chassii are listed.

Zeno:smoke:

On breaker we used Mallorys. They had a carry & break rating.
The hoz outs alone are good for 240ma.
You can try pulling all the low level tubes & leaving in the hoz AFC, H osc,
2 hoz outs, damper, HV rect and HV reg. BTW I looked, can someone
post the PS schematic ?
Also does anyone look at an OLD Sams index & see if there are any
PCB's on this set ? I have a 2001 & for some reason none
of the TS chassii are listed.

Zeno:smoke:

this is the only one I know of.
https://www.earlytelevision.org/pdf/motorola_ts-907_sams_739-3.pdf
seems all point 2 point.

this is the only one I know of.
https://www.earlytelevision.org/pdf/motorola_ts-907_sams_739-3.pdf
seems all point 2 point.

The only pre-WID rectangular-color tube motos I have seen are hand wired and looked like what you'd get if a Zenith TV and a car radio had an illegitimate kid.

I think moto kept their color TVs hand wired till WID came along.

The only pre-WID rectangular-color tube motos I have seen are hand wired and looked like what you'd get if a Zenith TV and a car radio had an illegitimate kid...
:lmao:

1971 Sams index shows no bulletins.

Ok got an update the 6gk6 pin 1 150 ohm resistor to ground burned up changed the resistor and that one started getting real hot so I pulled the tube and put the old one tube in and it didn’t get hot again but at the same time the old tube shows very little emission on the tester so this resistor may not be getting hot because the tube is bearly conducting. So I have to wonder why this is happening with a new tube either the tube is defective or something else is being affected in the audio circuit. And with the old tube in all the voltages came back to normal so this was the problem area. So what possibly could cause this when the tube conducts.

Ok got an update the 6gk6 pin 1 150 ohm resistor to ground burned up changed the resistor and that one started getting real hot so I pulled the tube and put the old one tube in and it didn’t get hot again but at the same time the old tube shows very little emission on the tester so this resistor may not be getting hot because the tube is bearly conducting. So I have to wonder why this is happening with a new tube either the tube is defective or something else is being affected in the audio circuit. And with the old tube in all the voltages came back to normal so this was the problem area. So what possibly could cause this when the tube conducts.


That's almost always caused by excessive grid leakage, IE g1 being pulled WAY too high ( off 0v) forcing the tube full on, C55/C56 bad / leaky? If there were at one point, the output T5 may be damaged, and needs to be tested, but it says 0v at pin 2 of the 6gk6, if you do not see this when it's up and running, C55/C56 are leaking the 90v from the det.

and do check the output x-fomer.

The audio trans checks good so are you saying the tube is good and it my be a cap ? Because the tube gets extremely hot in a short amount of time like it’s full on.

Check for voltage at pin 2 of the 6gk6, or the volume cont, ( same circuit ), if not 0v or close to, then you need to find why it's not.

most likely bad caps.

way too much info on the subject! :D

http://www.geofex.com/ampdbug/coupling.htm

Pin 2 is showing 55mv and the tube is slightly red plating.

And it's quite normal for miniature output tubes to get hot enough to burn your skin off, but smoking the cathode resistor is NOT normal.

No it’s not normal but it was nice to see the voltages normal now I have to find the cap culprit.

Here is an example of a breaker with ratings
IIRC the hold is max amps that will not give accidental trips.
The break is for instant trips.
https://www.tedss.com/CBT400/

Thermistor seems just to prevent high cold set inrush current.
Should go to 0 ohms hot. You can jump it out to test.
When its cold you can put an ohm meter on it & heat it with a heat gun
etc & watch it drop in value.
BTW most thermistors that fall apart can be soldered back together to get you by.
Now if you leave out the 6GK6 you can work on everything else.

Zeno:smoke:

https://frank.pocnet.net/sheets/049/6/6GK6.pdf
55mv (0.056 V) Is infinitesimal, not enough to be causing the problem, you have something else going on here.

check check and re-check

Primary of t5 (930 ohms)
C55/C56/C57/C58 ( All but c57 rated 1kv or higher)
6gk6 tubes, they may be bad even if tester says they are OK.
Make sure the output transformer is good and all caps are of good quality, you could be having a problem with parasitic oscillation, (high freq) that is overloading the output.

One thing to try is to ground the center pin ( wiper ) of the volume pot, this will force the grid to 0v, if you STILL red plate, then you know the problem is something else.

And I believe it’s the tube I have the chassis on the bench and tube in the resistor gets hot I pull the plug then plug back in and resistor stays cool it seems to be random and those 2 caps they only matter if the plug is in to complete the volume circuit so that really don’t leave much but the tube or a .005 pin 8 cap because it gets hot all plugged in and complete or on the bench.

1.4 ohms secondary primary .933 ohms comes up as k ohms. That’s good.

Do try what I mentioned, tie the center of the volume control to gnd and see if it stops getting hot.

The volume control is not plugged in this has become a random thing one moment the resistor and tube gets hot then it don’t even not plugged into the volume control so it don’t matter at this point if the chassis is in or out. Now it’s looking like a defective tube or as the schematic shows a .005 to ground with a 145v source on the other end but the sams don’t show that it has 2 .005 caps not one.

W/o that volume plugged in, there is nothing to keep that grid pulled low, and it will float high, causing the tube to bias on.

If it keeps acting up, what I would do is.

Replace BOTH c54/c56 with something like 667-ECW-H20103HV & c55 with something like 667-ECW-H8102RHV , and so on.
There is a tie to boost voltage via r82, but since there is no diode on this line, this means there is a strong horz pulse there, c54 is there to filter that, c56 is there as bypass and let only audio to the output stage, if ANY of these caps are faulty, DC and/or horz pulses can be passed on to the output.

What does the x z and w represent. Can a ceramic disc intermittently leak or short.

667-ECW-H20103HV & 667-ECW-H8102RHV are mouser part numbers
I did not wanna paste huge links here
tiny links
https://tinyurl.com/2p8apn29
https://tinyurl.com/yvbjsc9k
ceramic discs normally dont give problems, BUT, it does not mean the never do.

paper caps. ALWAYS BAD.

Vintage film caps and Mica, most of the time, don't act up, but I HAVE seen them cooked to death and bad before.
https://imgur.com/veMo2go
these are from my CTC-16XL and were causing color problems.

in other words, you must treat all old caps on a case by case basis by diagnosis ASIDE from the paper and electrolytic, which you will always assume to be bad.

My dvm has a capacitor mode to check them and it’s a great thing to have but even though they check good in circuit and under load I know is a different story. It can check uf and nf.

My dvm has a capacitor mode to check them and it’s a great thing to have but even though they check good in circuit and under load I know is a different story. It can check uf and nf.

correct, a DVM cant test for leakage.

Hey thank you for all the help you have been offering me I do appreciate it.

=^-^=

sneaking onto here helps with the boredom @ work!

" OH GREAT, THANKS! 25 MORE PRODUCTION BOARDS FAILED, YOU WANT THEM DEBUGGED BY WHEN!?!?" :scratch2::yikes:

Lol ��

This 150 ohm resistor if it burned up down to 95 ohms would this alone cause the tube to go full on ? If zero ohms at pin 2 will cause the tube to go full on then how can the tube go full on if there is any voltage getting past c55 and c56 that would have voltage at pin 2 so I would think if it’s not zero and there’s voltage present then the tube wouldn’t be full on. I checked the volume pot it measures 2.4meg wiper varies ok. So just changing the burned resistor should this fix this at all.

The 150 ohm cathode resistor is for limiting current, even if it was not there, it would not overload the tube.

The only thing that could is too much positive voltage on pin 2.
And as stated before, W/O the volume control plugged in, there is nothing to stop the grid from creeping up and turning the tube on, this is a design flaw.

Ok well maybe at some time of the history of this set maybe someone had unplugged the harness that carry’s the volume control and it burned the resistor so I’m still not sure about the tube. That’s the only one wire on the volume control that goes to pin 2 so with all hooked up the tube shouldn’t run away but if it does then I don’t know from there. I changed all those caps you mentioned and the booster leg with the 1.5 meg resistor is good. Or maybe between the plug connector maybe a bad mate within the plug itself.

You could always hook your DVM to the center post of the volume control ( wiper ) with the set in operation, and move the control through it's entire range, you should not see a voltage much higher than 0v, a few millivolts are not enough to cause a problem, but 2-5v or more, PROBLEM! :O

I checked continuity of the wires on the volume control as well as the changing ohms when I rotate the knob it all looks great.

I checked continuity of the wires on the volume control as well as the changing ohms when I rotate the knob it all looks great.

The method I described is an easy access way to monitor the voltage on pin 2 of the 6gk6 with the chassis in set, the center of the volume pot is more or less directly connected to that pin, by watching the voltage there, you are also watching the volts on that pin.

Yes that’s the green wire goes to pin 2. So now I have to change 2 .005 discs and got another tube coming hopefully Friday. Then put it all back together and hope no more load pulling down the b+.

Well putting the chassis back in so if I still have this b+ being pulled down then all I can come up with is a bad cap to ground I don’t think a resistor would do this because it just seems like maybe one b+ voltage is bleeding over to another via a cap to ground. Pulling all tubes one by one with chassis in hooked up didn’t show anything positive.

All back together and the audio output tube is new and still getting really hot fast voltages still low and the green wire on the volume pot goes directly to pin 2 and there is 280 ma at that pin the volume pot is 2 meg it measures 2.4meg if pin has to be zero I have no clue why there is 280ma there. Still looks like this audio circuit is pulling the b+ down b+ down means all other voltages go down with it. The volume pot has 3 connections green blue and ground which ground is on the body of the pot and one end of the pot maybe the ground is picking up stray voltage from somewhere else and back feeding the pot. I don’t know at this point. If the tube is at zero volts then it will run full but with 280ma then the tube should not run full even chassis out pin 2 still showed around 50-60ma. Now I have discovered that the 1st video 6aw8 and the video output 6hb6 are getting hot fast within 30 seconds being on so I’m off now to look at that circuit.

Hi Guys, It is good o see you have made progress on this set. So If the audio tube is
getting hot and is possibly the current draw, it should be easy to figure out what might
be wrong. First turn it on and hook up a quality audio signal to the volume control,
make sure you put it through a .1 uf cap and see how it sounds... Good quality or not?
Does the audio output transformer measure 930 Ohms? Is there approx 145V on pin 8?
If you are reading .25V on the grid & Center line of the volume control, check out R80,
R81, R82, be sure they are right.
Also there are other goodies to think about., like crudlies on the tube socket pins allowing
little bits of current to flow and give you small voltage at pin 2 the grid to the tube.
I Assume Timmy that your 280ma. at pin 2 is actually .28V small typo.
I Also found I kept making the same typo earlier in this thread saying 380ma. for the
power supply current, when it's actually 580ma, as others have correctly written......
Also you should be able to ground pin 2 without causing any harm, and see if the tube
runs cooler, & Your PS voltages return to normal.....

I'm a big fan of voltages being pretty close to what the schematic says, but .25V is kinda
small for that spot.

As it is, when you run the set do you get sound, or snow from the sound when you turn
up the volume ? does it sound like it should? Clear not distorted?

Also remember single tube audio output circuits like that are Class A Amplifiers, so the tube
is biased on anyway, and always, otherwise you would hear distorted sound as each
sound would be turning the tube on and off all the time. Class A Amplifiers are always
conducting, and the input signal smoothly changes the grid voltage & smoothly raises, &
lowers plate - cathode current to give you a nice smooth sound.



.

I could answer all you wrote if you want my number let me know it will only take a few minutes so much typing lol. The audio trans checks perfect 80-81-82 resistors perfect and after having the set on the last time I had an antenna on channel 3 fades alittle probably out of tune but channel 4 sound was perfect but heard no snow with antenna off and yes I made a mistake pin 2 is a green wire is the wiper set on it measured 280 mv But the tube didn’t red plate until I had the chassis out and found the 150 resistor burned. The tube just seemed to get really hot fast now I find within 30 seconds the 6aw8 and the video output 6hb6 get really hot fast I have read that low b+ is not good for tubes maybe things change with the tube conducing at low voltage. My initial finding was I had no video so maybe something in the video area causing all this.

It is always possible you have more than one problem. If you suspect the Video Output
tube is using too much current, then you need to do voltage checks at each pin & see
if you find any burnt looking parts in that circuit. It's also sourced to the 385V.

The video amp 6AW8A is also sourced to the 385V.

But if the audio out tube accounts for all the extra power supply draw, then we may be
getting ahead of ourselves.


.

That’s just it there is nothing I’m finding resistors check perfect it makes no sense I thought maybe something in the convergence but I don’t think there is any high voltage points there to pull it down.

keep in mind, as stated before , audio output tubes always tend to run hot, as do horizontal outputs, this is just par for the coarse and does not mean there is something wrong.

Ok maybe so but I still have the low b+ and no video and I went over the video amp and output and found nothing I did suspect the 1n60 but I do have sound.

If the sound is clear, and you replaced the cathode resistor, and that circuit seems ok,
then it's time to check the next circuit. It may seem frustrating because there is no
dead short, and everything mostly works, but somewhere you may have a tube
with bad voltages on it, improper biasing, and using too much current.
It will take time to find it, Most likely with tedious voltage checks.

.

You still have yet to get a decent DVM that has a decent amperage range to check what current draw you really have at L54 right after the voltage doubler.

And until you can do this correctly, as you have stated that the meter you have does not have the range to do so, you are just going on assumption.

GET A decent DVM and check the current at that point to see if it is indeed excessive.

this is an important step.

Going to try something I have been using a 10 foot extension cord to power this tv so with the resistance of the extension cord and the thermistor and using a power cord from a b&w tv very thin and an air conditioner running from same outlet maybe this will make a difference, excessive resistance would cause this.

Well that didn’t work but from the first day I plugged this set in it red plated one horizontal tube and it’s still doing that now only one tube and it’s now looking like the pulling down of voltage maybe in the horizontal the oscillator runs but after warm up plug in again the oscillator will not start again until it sets for awhile and cools down. I don’t know if the yoke would affect the horizontal oscillator from starting. This happened with the old flyback but I since changed the flyback with a nos one. Problem is the voltages across the board are still low it’s not like I can look at voltages and see that one rail is lower then the rest and go to that area b+ low everything is low.

hummmm Red Hot Tube Plates = Too Much Current.

Is G1 for each tube -45V?

Maybe you need to take a break from this tv for a few days......


.

The g1 was low to begin with so I turned it down more like not even a 1/4 up. Took the chassis back out to double check the 2 timing caps .0039 and .0068 it’s always possible I reversed them especially because the print on them is so small I should have used a magnifying glass that’s how small and yes I should get away from it. But only 1 tube, hmm.

here is the biggest help to know when hor osc is OK.

https://i.imgur.com/afNm19c.jpg

best investment you can make.

I know but it wouldn’t pay for me since I would use it once then put it in the closet lol ��

Not sure you are checking the right " G-1". We mean the G-1
of the hoz out tubes. They are in // to give enuf output.
Typical sets draw abt 210 ma this one IIRC 240, beyond most
hoz out specs. Thats why 2 HOT's. Others did it in the early days.
Admiral did & if you changed the FBT there were pages to mod the
set to use one 6KD6 H out NOBODY wanted to do them.
If that neg voltage is not there the tubes stay on too long.
See class C amps. !
Once one fries the other takes over. That one will overheat trying
to supply the HV but one cant keep up current demands.
Bottom line is without the proper G-1 voltage you will cook up expensive sweep tubes. Fix that FIRST if needed !

enuf fer now
Zeno:smoke:

This from the start didn’t do this all the time was random then it was ok now it started doing it again when the oscillator is running I have perfect hv. Maybe it’s because the b+ is low creating this. Only tube I can’t test is the damper.

I know but it wouldn’t pay for me since I would use it once then put it in the closet lol ��


So after this one your never gonna touch another TV again.... ever ????? :saywhat:

Stop making excuses for not investing in your hobby, screwdrivers & wire snips only go so far..... :rolleyes:

I bit rough but.....
We went out to a rib joint last week. I got a full rack & my squaw got
a half. It was a great feed & leftovers I measured my rack & it was
16" long. Next day I finished mine then the next day I took a dump and
it was just a memory. Nothing left but the CC bill.
A nice meter will usually last a lifetime unlike the ribs. Here today, flushed
tomorrow.......
So anyhows get the H OSC going FIRST ! The PS voltages are probably
a red herring.
And YES take a few days off. When we got a dog it got put aside & usually
another tech got it & fixed it fast. That tech was often the shop idiot !!

73 Zeno:smoke:
LFOD !

So after this one your never gonna touch another TV again.... ever ????? :saywhat:

Stop making excuses for not investing in your hobby, screwdrivers & wire snips only go so far..... :rolleyes:

Unless you sell all your tube electronics or stop using them permanently you will encounter another problem where having a scope will be helpful. Test equipment is the one thing I'll probably never sell even if I were to dump 95% of my collection...I know if I sell it, a week later I'll need it bad enough to regret letting it go.

Dealing with this without a scope is like trying to win a marathon when one of your legs just got amputated yesterday and replaced with a peg leg... Dealing with this with a DMM that isn't sufficient for the job is like running that marathon with only one leg, and that leg is the peg leg...

That said if your meter has a dedicated DC Volts setting you can measure DC current as a voltage if you have a power resistor of a known value. Connect a 1 ohm or 10 Ohm power resistor in series with the cathodes, clip your meter across the resistor and measure DC voltage. DC current will equal measured DC voltage divided by resistance of that resistor...A 1 Ohm will make the math MUCH easier.

The shop idiot was a rotating position, Everyone got to be it at least once........

Same with Shop Genius....

Smoke a few high dollar Horizontal Output Transistors and your title changes fast!


.

Scopes are a funny thing. Up till the late 70's we almost never used them.
Then they became indisposable on new sets. So much so we started using them on old sets instead of plugging at them with a Simpson 260 or
RCA volt-ohmist. I thing almost any tube set can be fixed with a good meter
and a ringer for yokes & FBT's. It helped we bought the Sencore suite
then another all on crash carts. New stuff took the fustration out of
test leads etc. Sencore also used to publish a LOT of how to stuff
that was of great help.
Anyhoo time to finish my ale & hit the sack. & GB all my VK friends.

73 Zeno:smoke:
LFOD !

Unless you sell all your tube electronics or stop using them permanently you will encounter another problem where having a scope will be helpful. Test equipment is the one thing I'll probably never sell even if I were to dump 95% of my collection...I know if I sell it, a week later I'll need it bad enough to regret letting it go.

Dealing with this without a scope is like trying to win a marathon when one of your legs just got amputated yesterday and replaced with a peg leg... Dealing with this with a DMM that isn't sufficient for the job is like running that marathon with only one leg, and that leg is the peg leg...

That said if your meter has a dedicated DC Volts setting you can measure DC current as a voltage if you have a power resistor of a known value. Connect a 1 ohm or 10 Ohm power resistor in series with the cathodes, clip your meter across the resistor and measure DC voltage. DC current will equal measured DC voltage divided by resistance of that resistor...A 1 Ohm will make the math MUCH easier.

While I didn’t get an exact ma from L54 it does measure up perfect in ohms the ma would show higher then 580 if the voltage is being pulled down so obviously voltage is being pulled down and obviously affecting the horizontal oscillator so if everything I check from coils and resistors check good there is ceramic disc caps so if there is one leaking to ground back feeding another circuit causing this problem how can I get an idea if stray voltage is making it to ground. Is there a way to check ground in such a way to see if there is voltage there that shouldn’t be there.

In all the many sets I have restored, 10+ (lost count now), I have only had one occasion of an horizontal output tube red plating, ( Magnavox ), and this was due to a defective damper.
Truth is, you have picked a rather hard set to work on, even for experienced vintage TV buffs.

The dual horizontal outputs is a perfect example of this, not sure why Moto chose this over a single larger tube, because it only make it more complicated.
If you have not done so already, it is highly recommended that you get a matched pair of 6JM6s, where this is not critical, it will insure that the horizontal output circuit is working at optimal efficiency.

Yes I got 2 new RCA tubes and one started to red plate but I pulled the plug. So if the damper is bad would it pull the voltage down along with red plating a tube. I have a new damper I wasn’t able to check the one in the set. The only other thing I found that I missed was a 25 v150 uf cap to the contrast and brightness but it checks at 223 uf so I’m changing that one. It seems once chassis is in and the convergence and tuner are plugged in then the voltage drops but the convergence is low voltage don’t think it would pull b+ down the way it is.

Yes I got 2 new RCA tubes and one started to red plate but I pulled the plug. So if the damper is bad would it pull the voltage down along with red plating a tube. I have a new damper I wasn’t able to check the one in the set.

New does not necessarily mean matched, though you may have difficulty finding them, they are sold in pairs that have been tested to work well together, no 2 tubes are exactly alike, and it prob won't matter THAT much, but in a situation such as this, it is always better to use a matched pair over a non-matched.
Like sold here.
https://www.vivatubes.com/nos-matched-pair-sylvania-usa-6jm6-grey-plate-2-side-o-get-vacuum-tubes-100/
out of stock :(

In all the many sets I have restored, 10+ (lost count now), I have only had one occasion of an horizontal output tube red plating, ( Magnavox ), and this was due to a defective damper.
Truth is, you have picked a rather hard set to work on, even for experienced vintage TV buffs.

The dual horizontal outputs is a perfect example of this, not sure why Moto chose this over a single larger tube, because it only make it more complicated.
If you have not done so already, it is highly recommended that you get a matched pair of 6JM6s, where this is not critical, it will insure that the horizontal output circuit is working at optimal efficiency.

I had the last of the 28 tube Motorola's, the ETS908. We ran the set 5-8 hours a day! It only required a few tubes, here and there and never any circuit work.
It lasted about 10 years, used until the 23EG got too weak to show a decent picture. It still had the original 6JM6's.

I had the last of the 28 tube Motorola's, the ETS908. We ran the set 5-8 hours a day! It only required a few tubes, here and there and never any circuit work.
It lasted about 10 years, used until the 23EG got too weak to show a decent picture. It still had the original 6JM6's.

I guess I'm just lucky that the 25AP22A in the Hoffman Colorcaster I found is in fair condition, it too originally came with a 23EG when it was new, still trying to find another tube, blue gun is weakest. :(

As it is now I’m going to look at the convergence panel which has 5 200v red caps. It also has a selenium diode don’t even know if that maybe shorted there was no smell to say it burned up but this voltage drop is when the convergence panel and tuner is plugged in. But have to check everything maybe this route will show something.

As it is now I’m going to look at the convergence panel which has 5 200v red caps. It also has a selenium diode don’t even know if that maybe shorted there was no smell to say it burned up but this voltage drop is when the convergence panel and tuner is plugged in. But have to check everything maybe this route will show something.

That most likely won't get you anywhere.

there is no bias going to the convergence circuits at all, it's fed by horizontal and vertical pulses from the respective transformers. No boas needed at all
the vertical output has a convergence tap on it, the horizontal shares the same feedback winding on the flyback that is used for horizontal AFC and color sync.
in fact, you can unplug the convergence circuits completely and still get HV, you will most likely see a partial collapse of vertical range.

I dont know half of what you guys know when it comes to these tvs but I don’t get why the voltage drops once they are plugged in. Can I test the selenium diode with a dvm.I have noticed that when the vertical is running you can usually here it at the yoke all my other color sets I was able to here it this one I don’t. So if the vertical is not running that maybe pulling down the b+ since there is a 385v on the primary side of the output transformer or maybe no running at the correct speed.well I know if the vertical quits then I have a horizontal line but maybe not running at correct speed.

the answer to that is no, for the most part, a DVM can not test selenium diodes, the diode test feature was made for SI/GE types which have a much lower junction barrier voltage, and thus trying to test selenium will always look bad to them.

I dont know half of what you guys know when it comes to these tvs but I don’t get why the voltage drops once they are plugged in. Can I test the selenium diode with a dvm.I have noticed that when the vertical is running you can usually here it at the yoke all my other color sets I was able to here it this one I don’t. So if the vertical is not running that maybe pulling down the b+ since there is a 385v on the primary side of the output transformer or maybe no running at the correct speed.well I know if the vertical quits then I have a horizontal line but maybe not running at correct speed.

I have said it, and so have many others, you need to get better equipment, because now, you are just going on assumptions, and as long as you are, you will keep going in circles no matter what you try to do.

You NEED a better DVM that can measure the current draw right after the main diodes, you need to know what the draw is with NO guessing. 580ma? more? less?

And as others have said, you need an o-scope.
is the ripple after L54 1.5v? more? less?

ALL OF THIS is important, And can't be done with what you have right now.

I know I know but I cannot spend crazy money for just this set nothing in stone that says I’ll be working on more sets in the future so with that said one day in the very near future I’ll post when it’s fixed. I have nothing else to do during the day.

Wasn't this set listed on eBay for like $225 before you bought it (I remember because before the ETF meet I was considering buying it)?

If you choose wisely you could get 4 scopes and a decent budget DMM for what this set cost.

It's definitely time to throw in the towel on this set and cut your losses.
You've learned from this encounter.
Don't feel bad; it happens to all of us in life.
There are future projects with your name written all over them.

I have pointed this out before.

https://www.amazon.com/AstroAI-Multimeter-valentines-Resistance-Capacitance/dp/B08FDH8845/ref=sr_1_34?keywords=dvm+multimeter&qid=1661882160&sr=8-34
https://www.amazon.com/Crenova-Auto-Ranging-Multimeter-Measuring-Backlight/dp/B00KXX2OYY/ref=sr_1_7?keywords=dvm+multimeter&qid=1661882412&sr=8-7
https://www.amazon.com/Multimeter-Continuity-Multimeters-Multifunction-Protective/dp/B08LD6PDQQ/ref=sr_1_8?keywords=dvm+multimeter&qid=1661882412&sr=8-8
https://www.amazon.com/Ranging-Digital-Multimeter-Battery-Alligator/dp/B06ZZG2F2N/ref=sr_1_6?keywords=dvm+multimeter&qid=1661882412&sr=8-6


here is 4 examples of what I call cheap throw away DVMs, I have 3 like these, which I use for risky testing, and not afraid to damage them, 95% of the time they agree with my high $ Fluke meters, which i use when i want best accuracy, like alignments.
The cost is so low on these, no reason not to have 1 or 2.

here is just a few hand held o-scopes.
https://www.amazon.com/Quimat-Oscilloscope-BNC-Clip-Assembled-Finished/dp/B07QML4LJL/ref=sr_1_5?keywords=oscilloscope&qid=1661882888&refinements=p_72%3A1248921011&rnid=1248919011&s=industrial&sr=1-5
https://www.amazon.com/Oscilloscope-Multimeter-LIUMY-Professional-Automatic/dp/B08832JX4H/ref=sr_1_3?keywords=oscilloscope&qid=1661882888&refinements=p_72%3A1248921011&rnid=1248919011&s=industrial&sr=1-3


not so cheap, and will take a bit to learn to use.

Yes they are nice good prices as for the dvm there is no need to condem the one I have already only my meter don’t go above 400ma but right now what good would it be for me to know what the ma is I already know there is a draw down so to look at a meter showing me 700-900ma won’t tell me where it is only that it’s drawing more then it should be which I know already. And the horizontal oscillator loss is due to the current draw on the b+.

But right now, you are working in the dark, you need to know what it is exactly, other than beyond the range of your meter (400), is it taking 500ma? 560? 580? 600-610ma? All of this will be telling you something, you have to know what the draw is first, then if it's too much, then look for the reason of the draw, if it's not, like below 400-500ma, then the power supply may be having a problem putting out enough power in the first place, this would be evident by excessive ripple output, which would wreak havoc with all circuits.

Ok I have another dvm I’ll have to see if that one goes above 500ma and if there is excessive ripple then that would mean bad caps or maybe diodes and what’s going to show me ripple other then a scope.

Yes, bad/weak diodes or leaky caps (c151/c152) would cause excessive ripple before/after L54, and limit the power output, thus the wave seen at L54 would be much higher than 1.5v ptp, and the power supply would be struggling to put out full power.
On the other hand, if it is overloaded, like say over 600ma, then the problem is external, as others have said, don't take the 580ma as gospel, expect -/+ 10%
But the first step, as others have said is to know for sure.

The other meter to low so that’s out but I did look at the dvm I have been using and the range says in the book 400ua 0.01 and the other 2000ua 0.1 so maybe I had the range wrong.

The other meter to low so that’s out but I did look at the dvm I have been using and the range says in the book 400ua 0.01 and the other 2000ua 0.1 so maybe I had the range wrong.

it just does not have the range needed, 2000ua = 2 milliamps.

you need something with a 10a range, cause you are dealing with 500ma 1/2a almost.

Ok so the crt holds lots of voltage even after turned off so from the beginning I’m getting buzzed from the hv cage even when off so I may have hv leaking to ground.

Yes, it's a giant storage capacitor, and it will always find ways to get you!
Best to discharge the anode after it's been on so you don't get zapped, it can't really hurt you, unless you have cardiac issues, as it can scare the crap out of you, and cause you to yank your hand back and cause nasty cuts in the sharp edges all around.
If I had a dollar for every time I have been zapped working on TVs and such, I would have been able to pay my mortgage in ½ year!

There is even ways to have fun with the HV, if you are A) dumb, and B) know what you are doing, like this guy.

https://www.youtube.com/watch?v=Rb6vMgurAH0

It’s very little I’m feeling I don’t think the hv should make it to ground in that way enough to actually feel it. So I guess it’s not possible for any amount of anode voltage making it to ground wouldn’t cause any problems, I feel it could because after all all the circuits wind up at ground. I know I’m grasping at straws at this point but maybe I should try another regulator tube maybe it has a heater short.

Most likely grounding issue.
The HV cage is screwed to the main chassis, so they are direct connected, the CRT is grounded via aquadag on the outside, normally via a spring touching it, can't be sure about yours not having seen it.
This assembly is normally built into the entire CRT mounting assembly, and grounded at the bottom by a metal strip that touches the main chassis.
If for some reason this does NOT make good contact, then a difference of potential can happen, which can result in unpredictable operation, so usually, when I work on a TV and the chassis is not firmly screwed in the cabinet, I always have a clip lead from the chassis to the CRT mounting assembly for extra safety.

It does have a spring it’s tight and the tube is clean. Is it at all possible that the hv could do what is is from a possible heater cathode short in the 6bk4.

It seems like a short like that could risk smoking R141, and R213, so it's unlikely.
6bk4 pin1 at 380v via R141 (1k) heater z to gnd via R213 (68k) , if shorted, I think something would have to give.

Well maybe this is pulling the b+ down.

Well there is one 450v 80uf cap for the b+ that I’m going to change because I already changed the 160uf caps thinking maybe they were bad but made no difference so I’m going to change that one since even if it checks good it could still be bad don’t know the esr of the cap and maybe it cooked inside from the frequency of the b+ circuit. And after all the cap has a name I never heard of, cheapy.

Changed all power supply caps now all nichicon caps big increase in the b+ but it’s still being pulled down to the point where the horizontal oscillator won’t run then it draws even more and the hot tube again red plates so on the bench this don’t happen but after I put it back in the cabinet and plug everything in this is when it happens so at this point I’ll have to sit on it for now. Baffling to say the least when the oscillator runs I have excellent hv but that’s only when I first plug it in once warm up pull plug put back in no oscillator and big draw. Oh well. The veritcle centering pot after turning more then half then it varies very little I have to think maybe it’s shorted it’s wire wound and has a 385v feed to it or possibly a shorted turn on one of the sections of the verticle output transformer got to think of everything at this point.I guess now I’m going to check voltages on the tubes.

Does a 1n60 diode go partial bad or it’s good or not good. And with the mention of injecting a composite video source does that mean like from a vcr with a .1cap. As for voltages they are there now after changing the damper. Pin 7 of the 6aw8 shows 13v so at test point b is that supposed to be 5 volts to say the diode is good?

Changed all power supply caps now all nichicon caps big increase in the b+ but it’s still being pulled down to the point where the horizontal oscillator won’t run then it draws even more and the hot tube again red plates so on the bench this don’t happen but after I put it back in the cabinet and plug everything in this is when it happens so at this point I’ll have to sit on it for now. Baffling to say the least when the oscillator runs I have excellent hv but that’s only when I first plug it in once warm up pull plug put back in no oscillator and big draw. Oh well. The veritcle centering pot after turning more then half then it varies very little I have to think maybe it’s shorted it’s wire wound and has a 385v feed to it or possibly a shorted turn on one of the sections of the verticle output transformer got to think of everything at this point.I guess now I’m going to check voltages on the tubes.


Good Morning:

After reviewing the posts since I was away, All I see of any significance is this
post about Horiz. Output tubes overheating.

You don't need to look anyplace else. If the 6JM6 is so overloaded that the
plates glow red then this is a problem. Max ratings for that tube are 175ma
cathode current, The tv schematic shows 120ma each tube cathode current.
I would assume around 220ma it will begin to overheat, 260ma maybe red
hot plates?? This would be a source for lowered power supply voltages. If
only 1 tube overheats that means only 1 has a problem, Possibly not the
Osc. but you have to figure it out. Cathode current readings for each tube
will show what's up.

6JM6 Specs: https://frank.pocnet.net/sheets/127/6/6JM6.pdf

This tv uses 2 6JM6 tubes in parallel, so 2 nearly identical circuits that should
have the exact same voltages on all the tube pins - This is a place to start.
Also cathode current and screen grid currents are printed on the schematic.
You need to check them and see what's going on there.

-45V on G1's most important voltage to measure. You should check all the
parts in the Horiz Osc, & Output section, All Voltages, & Sorry to say but
at some point the wave shapes at input of 6BL8 & 6JM6's. Be sure there is
no DC component making it's way to the G1's.


I would focus my attention here. If an Osc. sometimes does not start, then
you can be sure it's not running properly when it does start, lower output,
possible misshapen signal to the 6JM6's.


I gotta go, see you later on.... Good Luck....



.

What was happening is I was turning the horizontal hold- oscillator and that’s what was making the oscillator stop or not start so both hot are at -45v I adjusted the coil voltages look good on the oscillator tube but now I’m trying to figure out why I cannot get an image on the screen so I’ll have to figure out a video source to try or the video detect diode may be bad. But I fear that the L6 may have been fooled with because inside looks like it has been turned but I do get something on the screen but can’t make out if it’s a distorted image it changes using the fine tune and it comes close. I still have sound. If L6 was turned from what I see on the screen then it may not be to far out. And b+ voltages are good now since I changed the damper.

If you do indeed have stable HV, (congrats on that! ) , you should now try what both I and EM has suggested, feed in a composite video signal to Point B, from a VCR or DVD, through a isolation film cap of .01 or so, the level will be lower than the set needs, but you should see something, and be able to get lock, also, removing the 3rd if tube V3 when you try this, don't focus on sound or getting a signal in from the tuner yet, see how it looks with video input, then go froward from there.

The input at point B is based on this, https://antiqueradio.org/A-V_AdapterForVintageTVs.htm
I used this for reference several times, as when the status of the tuner/ IF is unknown, I have always used video input as a starting point.

Ok it worked out good so now the video amp and output works so now I’m looking at possibly the 1n60 or L6 was touched.

Good! Very good! :)
That means everything from that point forward is OK, including color.
Now all back from that point should be looked at, like the resistors in the IF, especially the ones on the cathodes, they love to drift out of tolerance the most for some reason, and yes, sometimes the detector diode does go bad.

You mean the resistors going to ground.

Yes, realistically, all of them should be checked to see if they are still in tolerance, but I have seen that the lower value ones on the cathodes are the ones that tend to drift the most in sets, this may not be the case here, but I have seen this 85% of the time, and it's always good to check for this, as if resistors are out of tol in the IF, it will make tuning in things nearly impossible.

Ok well I’m off to finding bad resistors hopefully and not the video detect diode which is almost impossible to reach. I was a bit amazed at how decent the picture was. These resistors I should check are off each IF tube ?

You will just have to hunt around, there is no telling, for example, the RCA CTC-16s had a bad habit with faulty R48 (150K) R50 (180K), and a few others, my rca 630ts clone had all bad 39 ohm cathode resistors in the IF, same with the Stromberg Carlson TV I did, 47 ohm as did the Arvin, which also had 47 ohm on the cathodes.
It seemed more than coincidence that they had bad resistors in the same places more or less.

Well I went over all resistors on all 3 IF tubes and the only one on 2 was a 1.6k that measured 2k that’s it. Is it likely that a disc to ground may be bad ? I still have a hunch that L6 may have been touched it looks like it was moved looking in the adjustment hole. Do you know how to check a germanium diode get a reading on ohms both ways where one side flashes numbers back and forth. And so again if there is sound then the video rides along so I think I could exclude the tuner.

there is a diode check feature on your meter.
http://www.instrumart.com/assets/uei-g2-phoenix-manual.pdf
you have to make sure it is diode mode, not sure what button to press but when in the right mode, a diode symbol should be seen on the display.

https://www.youtube.com/watch?v=Rj9WpoaX2Gk
how the test is done

there should be easy access via pins 2 and 4 at L6.
diode mode is the only way to really test it.

resistance checks wont tell you anything, in diode check mode, one way should be about .5xx on the meter ( give or take) and the other much higher, as seen in that video.

That diode test is for silicon diodes the one in the set is a germanium diode much different in diode mode the germanium diode does nothing no reading either way but different reading in resistance mode they are very sensitive and I have these diodes and compared mine with the one in the set and I have my doubts that it’s bad. I just thought there was a special way to check.

That diode test is for silicon diodes the one in the set is a germanium diode much different in diode mode the germanium diode does nothing no reading either way but different reading in resistance mode they are very sensitive and I have these diodes and compared mine with the one in the set and I have my doubts that it’s bad. I just thought there was a special way to check.

SI/GER all test the same way, it's selenium ones that you can not use the DVM diode check on.
you should be seeing a voltage difference when you change the leads back and forth.

I don’t see anything in diode mode with a germanium diode that’s why I thought there’s another way to test them.

I don’t see anything in diode mode with a germanium diode that’s why I thought there’s another way to test them.

that can only mean the diode under test is bad, or the meter cant test it, which is unlikely.

If you have a replacement already then try the meter on it, if it does not show a reading, it A) not in the right mode, or B) not able to test diodes for some reason.

they test the same way
https://www.petervis.com/Radios/making-a-crystal-radio/germanium-diode-test.html

just give dif readings.

That is odd I have checked many diodes but not germanium diodes so I don’t know why it won’t check and that article I did see it briefly. I did try it on the diodes I have same result.

Ok I figured it out your right my meter does test them all I had to do was hit the select and it changed to volt.

Ok I figured it out your right my meter does test them all I had to do was hit the select and it changed to volt.

Great! :D

chances are that the Detector is OK in the set.

what you may end up doing is NOT trusting the tube tester, and getting a whole NOS set of IF tubes, and perhaps Tuner tubes, but that's just a suggestion.

Well I hope the detector is good and I even thought of putting in the old tuner tubes which showed shorts to see what happens and I also tried different IF tubes but still the L6 like I said it looks like it was screwed in and out marks left in the plastic sleeve both top and bottom.

Let's hope that;s not the case, cause if any if them were changed, then the level of difficulty to align it is very VERY high, needing very special equipment and skills to get it right. sweep marker generator + oscilloscope and LOTS of time / experience.
https://www.youtube.com/watch?v=fHeWbyFMF8A
https://www.youtube.com/watch?v=I1h5zNFvn_U&t=212s

NOT easy

Oh I know I hope not as well.

As of now looks like the diode is infact good it tests just below 3 so that’s good. Now after finding no bad resistors in the 3 If tubes areas I have to figure where to go from here.

As mentioned before, it's best that you have a set of known good (NOS) IF tubes, 2, 6EH7s 1 6EJ7, and new tuner tubes.
And it looks like you have the coil/core type tuner vs the rotary switch type, these type have a bad habit of getting dirty contacts (black), making tuning impossible, the best way most have found to clean them was to remove the tuner cover, and clean them with a pencil eraser and solvent like isopropyl alcohol or the like, until the contacts are bright and shiny, making sure not to leave any bits of eraser behind.
If the tuner has not been cleaned already, there is a good chance that the contacts in there are all black and dirty and a source of trouble.

https://www.rfcafe.com/references/popular-electronics/images6/tv-tuner-popular-electronics-march-1967-4.jpg


best i can find on short notice

Hmm interesting well I’ll look at that and see what I come up with and at the same time I hope there’s no bad resistors in the tuner itself.

That is always possible, but due to it's nature, the tuner is a bit more forgiving with resistors drifting than other areas of the set due to the fine tuning, and the ability to adjust each core.

I pulled the cover and they actually look clean but when I touch the contacts they feel gummy or sticky maybe this is some sort of tuner lube. Maybe I’ll just clean the one that’s marked 3. Maybe alcohol is good to get the sticky stuff off.

Most likely an old cleaner lube that has broken down, I'd clean both 3&4.

If its really bad...

https://www.radioshack.com/products/radioshack-control-contact-cleaner-and-lubricant


but its almost impossible to get now. :(


I have 1/2 can left.

LOL!!!

Some maniac is trying to sell a can of it on evil-bay for $150!
CRAZY!

I got it for $10 last year! :O

Lol 150 bucks lots of sick people on eBay. And I have a half can of the same stuff from RadioShack but I just put the cover back on it was a real headache.

here is a thread about it.
http://www.videokarma.org/showthread.php?t=65178

And yes, the cover is easy to get off, a PAIN to get on, same on all sets.
The engineers must have been laughing a LOT about that!:D

Yup got to bend the tabs alittle bit and finesse it. I’ll have to put everything together and see what happens because I had the horizontal coil way out to get hv and since changing the damper and readjusted the hv and made sure I had -45v on the tubes so if the frequency is way off the can create a problem getting an image.thing is I didn’t try it with an antenna after changing the damper I only put the video in and got the image so I’ll try it together.