View Full Version : GE roundie


DaveWM
06-19-2012, 07:48 PM
picked this up today, will get to it later. Not my style but interesting chroma section. will get better pics don't have my camera right now.

zenithfan1
06-19-2012, 10:36 PM
WOW, that's cool! Especially since you are in the "land of no roundies" :) The GE sets rarely show up, even around here. Great score!

ctc17
06-19-2012, 11:48 PM
The riches of opulence abound in America, i would show my manliness to such a television receiver to my most desirable wife!!!! The television apparatus is so very fine. I wish I could shrink himself provides for very small, and to live in the list!
Your television make me feel very lucky and young in the before. I hope that you will hold it gently and add love. Please make picture after you restore
I think that television is very beautiful, I like this (large and vital thrust and solidity of television in micro-house myself!
This is the television reciever to be found in fanciful palace ruling class!!!!

Sorry Dave....I had tooo :banana:

zenithfan1
06-19-2012, 11:59 PM
I almost choked I am laughing so damn hard! This is the most funniness ever that I heard, I bow to your manliness! LOL^_^

Eric H
06-20-2012, 12:05 AM
Is anyone else having a problem seeing the pictures? I see the thumbs but they dont click.

mstaton
06-20-2012, 12:07 AM
Yes, they don't work

zenithfan1
06-20-2012, 12:27 AM
They don't work for me either.... I thought maybe it was a mini console:)

mstaton
06-20-2012, 12:32 AM
Maybe a 21 centimeter CRT.

Electronic M
06-20-2012, 01:29 AM
Yes, they don't work

Same here...I was beginning to wonder.

PS:CTC17, have you been smoking the same stuff as that Sanjarali cat?...Misa no standingunder what yousa sayin'.

tvcollector
06-20-2012, 05:28 AM
Pictures aren't working for me either..

Charlie
06-20-2012, 06:47 AM
Me either... but kool looking set from the little pics I can see.

old_coot88
06-20-2012, 07:03 AM
picked this up today, will get to it later. Not my style but interesting chroma section...
Wunner if that's the chassis that uses a NE-2 neon bulb in the burst gate circuit.:saywhat:
Had one in the shop one time with screwed-up color sync. Tried the usual tube subbing, voltage checks etc. and no luck. Then replaced the NE-2 and the problem was cured.
Strange, because the old bulb was lighting up normally.

DaveWM
06-20-2012, 07:38 AM
those were the craigslist pics, I tried to saving the image, since I don't have my camera right now. will get some better pics next week.

hi_volt
06-20-2012, 07:45 AM
Very nice set from what I can tell. I like the style.

DaveWM
06-20-2012, 07:55 AM
whats interesting to me it does not seem to have a color osc tube, so no zero beat adj or other freq control issues to fight. Looks like the same demod system as used on the porta color, just amp up the burst and let it ring. The chassis layout is like a CTC-15, but the PCB are def not RCA, the chroma and sweep boards are swapped (sweep near the back of the chassis) 3 tubes on the chroma (uses a compacton triple triode for the color dif amp). The audio is on the deflection board and the space where the audio board should be is pure power supply, just resistors/diodes (full wave)/thermistor.

bigger than normal speaker. Has had some sevice (PS board has some replacement resistors tacked on top).

Odd, red loop of wire coming up from the back of the PS PCB, looks like it jumps the thermistor, looks factory, and has been cut at the top. Maybe a factory option to use in sets that don't have a auto degauss? with the loop intact the thermistor would be bypassed? this set has the degauss hardware.

DaveWM
06-20-2012, 08:27 AM
looks like the CRT is near dead, cooking it now but not looking good. Oh well for 10$ I don't feel bad about it.

Zenith26kc20
06-20-2012, 08:55 AM
This set may have what is known as a crystal ringing color circuit (hope I remember that right). It doesn't have a color oscillator or a color killer. Burst excites the crystal and that provides the 3.58 signal. It is a bit weird to deal with.....

DaveWM
06-20-2012, 02:59 PM
pulled the HOT and VOT, dialed up the voltage to about 60v no smoke, went up to about 90v sound out of speaker (snow sound) see some wiffs of smoke around the replaced resistor, on of the cans feels a bit warm, but its right next to a big sand resistor. hmmm.

I am going to leave it at 45v for a while and try again, but looks like going to have to pull it and check those filters before risking a full power startup.

DavGoodlin
06-20-2012, 03:17 PM
Same here...I was beginning to wonder.

PS:CTC17, have you been smoking the same stuff as that Sanjarali cat?...Misa no standingunder what yousa sayin'.

Hey - at least no one here seems gislan.

DaveWM
06-20-2012, 05:18 PM
went a ahead and tried it again, after jiggling the RF amp tube I was able to get a clear strong audio. I will prob give it a shot in a while with everything in, keeping an eye on the HOT cathode current of course.

DaveWM
06-20-2012, 05:59 PM
good sound, HV comes up fine, HOT current about 185ma, horz just out of lock in range, can not flop the lines. Going to try some new tubes in a bit.

DaveWM
06-20-2012, 06:27 PM
new 6BH11 got the horz to lock it, color working but a bit weak, contrast weak, and some odd horz shifting like a hum bar, but not a regular moving event.

I am going to try a new AGC tube and video out. The horz locks but can't flop both ways (lock at the end of the range). there are a few ceramic tube caps on the sweep board. The vert sync is not strong but it is there. Need to check the basics like the B+ etc... waiting on the service manual book for that.

DaveWM
06-20-2012, 10:38 PM
well the ckt breaker popped so I guess I need to pull the chassis and check out the filters caps to see if they are shorting.

strike that not the breaker but a bad connection at the chassis interlock, but I do see a hum bar now so will check for HK shorts and if all good then will pull the chassis and check the filter caps.

DaveWM
06-21-2012, 06:03 PM
after testing a couple sections of the cans, which tested a bit low (50uf vs 80uf) AND did not respond very well to an attempt at reforming I decided to go ahead and recap. This set only has two cans wiith good access to them so they were easy to buzz off with the bone cutting saw. I then used a long sharpened piece of music wire to cut hole thru the bottom. the long drill make it easy to go thru the bottom without getting near any of the parts under the chassis. Going from the bottom lets you place the neg lead right at the edge near a twist tab, then place the positive lead right at the can terminal. this make it a bit easier since you dont have to try and configure the caps to have a central neg lead, I use radial lead caps since they are much less expensive and fit under the can well, I will alum tape the can back just to keep it there for reference. the other advantages of this method is you don't have to waste time trying to remove the old can, and all the lead dress can be left alone, just wrap the pos leads around the term and your done. After replacing the filters I will power it up again just to be sure I have not messed anything up, if it works then I will start checking some of the low voltage brown drops, as they have a history of getting "weak".

DaveWM
06-21-2012, 08:51 PM
argh, replaced caps still have a wandering hum bar, will check the rest of the tubes for HK, did not do the tuner/IF yet.

did adj the AGC, working as it should. Still very low contrast, I was hoping replacing the can caps (one was the video amp cathode bypass) would help there, no joy.

Got some other stuff to take care of so will have to give it a rest for a few days.

ctc17
06-21-2012, 10:44 PM
This set may have what is known as a crystal ringing color circuit (hope I remember that right). It doesn't have a color oscillator or a color killer. Burst excites the crystal and that provides the 3.58 signal. It is a bit weird to deal with.....

Yes, like the p0rtacolors. Seems to be much more reliable to me than the standard 6gh8 driven crap. I am always having issues with the color staying locked on the rca style sets.
The GE way of doing it always seems to work, its just very hard to get the color right. There are a few adjustments that are very touchy. I do have a NOS 19" GE with this decoder that works well though.

DavGoodlin
06-22-2012, 07:37 AM
Dave - is that the CB-21 chassis? I worked on quite a few GE from 60's but never saw that one. DG

DaveWM
06-22-2012, 07:49 AM
I think so, I remember seeing a C on the back will check later.

Chroma board as a bunch of trimmer pots on top and some trimmer caps on the bottom.

dieseljeep
06-22-2012, 10:32 AM
Yes, like the p0rtacolors. Seems to be much more reliable to me than the standard 6gh8 driven crap. I am always having issues with the color staying locked on the rca style sets.
The GE way of doing it always seems to work, its just very hard to get the color right. There are a few adjustments that are very touchy. I do have a NOS 19" GE with this decoder that works well though.

I always refered to the larger screen GE's as glorified Portacolors.
Proves out the meaning of the letters, GE. Good enough.
I got a few of those as freebees. I scrapped them all, as flybacks were bad. The last one I had, had an RCA hi-lite CRT that was perfect. I installed it in a Zenith roundie. Man, what a picture! I wasn't about to waste that great tube in a lousy Ge.:D

DaveWM
06-23-2012, 11:06 AM
using a brightner on it make the CRT produce an OK pic, good enough to continue trouble shooting anyway. There is something odd going on with the tint, does not really seem to phase shift from magenta to green like my oher sets (including my porta color). I have a service manual coming so hope to gain some insights into how to trouble shoot the chroma. The upside is the HV section seems fine, fly runs cooler than most other color sets. Still have to hunt down the hum bar and contrast issue (maybe just the weak crt on contrast). there is no bias adj on the CRT either.

old_coot88
06-23-2012, 11:26 AM
Does that one use a NE-2 neon bulb in the burst gate area? If so, it can cause color phase/ sync issues even though the bulb appears to be firing normally.

DaveWM
06-23-2012, 11:55 AM
Does that one use a NE-2 neon bulb in the burst gate area? If so, it can cause color phase/ sync issues even though the bulb appears to be firing normally.


Yes it does, it also looks blackened from the inside? Have not tried to observe it in operation. Schematic coming. I will have to see if I have any spare NE-2 laying around. the color demodulation seems to be working ok, it just seems like the tint control does little to shift the tint, does seem to effect the color saturation, not to the extent that the color control does though.

DavGoodlin
06-23-2012, 07:59 PM
Does that one use a NE-2 neon bulb in the burst gate area? If so, it can cause color phase/ sync issues even though the bulb appears to be firing normally.

I read in my book that the NE2-H was a recommended replacement. The grounding of the flyback aux coil (that triggers via this neon) may be faulty. This was an issue in the later rectangular chassis KC-KD-KE as well.

Edit: This book has a good bit of advise about alignment of the color circuit (a quirky GE exclusive). The predecessor chassis CA and those before were RCA design. The tint control is a variable capacitor for example. PM me if you want a copy of the 'CB' chapters.

DaveWM
09-04-2012, 10:31 PM
back on it again. Had a weak video out tube, that helped with the brightness.

I was getting all kinds of RF interference, a close exam showed some breaks in the balun mounted on the tuner. got that fixed up then I lost color. I think it was just the color pot grounding on the chassis when it was in the tuner mount on the back of the chassis. Of course I broke the neon bulb while putzing around on the chroma chassis so I went ahead and replaced that. While I had the chassis out I replaced the broken thermistor (it was just being held in place with pressure on the leads) with a CL-90. I also checked the schematic, the hacked in resistor was two 3.3k WW in P where there should have been a 680ohm...oy.... anyway I did not have a 680 on hand so I went with a 830.

there are some .1 brown drops (1kv) in the vert circuit that I will keep an eye on. I did not have any sweep issues but one of them sits right up against the 6EF7 and looks discolored from the heat. I don't like to make too many "fixes" on a working set at one time, so I will try it again and see if the color is working again. If it does I will prob pull the chassis one last time to go ahead and replace those, as well as the .0082 in the feed back and the .001 2kv snubber on the primary of the vert out (its one of those paper in hard ceramic tube shell types).

tvcollector
09-05-2012, 01:58 AM
I wish I could see pictures of this set.. It looks to be an interesting set..

DaveWM
09-05-2012, 07:56 AM
I read in my book that the NE2-H was a recommended replacement. The grounding of the flyback aux coil (that triggers via this neon) may be faulty. This was an issue in the later rectangular chassis KC-KD-KE as well.

Edit: This book has a good bit of advise about alignment of the color circuit (a quirky GE exclusive). The predecessor chassis CA and those before were RCA design. The tint control is a variable capacitor for example. PM me if you want a copy of the 'CB' chapters.

I have the GE service manual book, is your book the orange one vol one by Robert Goodman?

Some other interesting things about this set. The CB chassis I have is for the round CRT, but the same chassis was used also for the rectangle chassis with a plug in board for the pin cushion (if I am reading it right) My set also sports the later tint control that has a pot with a variactor diode to act as a phase shifting cap instead of the variable cap.

If all goes well I will pull the CRT to remove the lens today or tomorrow, there is only about an eight inch clear spot so it should come of easy.

dieseljeep
09-05-2012, 01:08 PM
I have the GE service manual book, is your book the orange one vol one by Robert Goodman?

Some other interesting things about this set. The CB chassis I have is for the round CRT, but the same chassis was used also for the rectangle chassis with a plug in board for the pin cushion (if I am reading it right) My set also sports the later tint control that has a pot with a variactor diode to act as a phase shifting cap instead of the variable cap.

If all goes well I will pull the CRT to remove the lens today or tomorrow, there is only about an eight inch clear spot so it should come of easy.

Then you people have the nerve to moan about the Motorola 6LE8 circuit.
I had one of those GE's that had a perfect RCA sourced Hi-Lite CRT in it. Needless to say, I scrapped that pig and installed the CRT in a Zenith. It was the last Zenith roundie they made. :yes:

DaveWM
09-05-2012, 01:18 PM
well the CRT is indeed a RCA Hi lite. At 1st the pic was not that great, but the last time I had it running with color it was looking pretty good that is after I replaced the video out tube. The Cabinet is blonde and in very good shape.

DavGoodlin
09-05-2012, 02:17 PM
I have the GE service manual book, is your book the orange one vol one by Robert Goodman?



Yes, it is.. I learned alot from those TAB books in HS because those 10 year-old sets started showing up on curbs and at VoTech.
My RCA vol 1 book by Carl Babcoke is tattered, bound with tape and smudged with notes, a treasure trove all these years later.

Funny thing is that Robert L Goodman also wrote the Zenith and Philco books the same year. Stan Prentiss wrote the Magnavox book and did a great job.

There are many I don't have in that series, but I just hooked a set of 14 of the books off ebay for $5 each, the original cover price. Hope to "get them for my birthday" next week:D

dieseljeep
09-05-2012, 06:52 PM
I bought a lot of those Tab manuals at the time. A lot of great imformation.
One of the quotes from the GE manual: " Color killer, Who needs it".
If you look at the GE schematics, you'll see a lot of simularity from the 1957 color circuitry design to the later offerings, such as the porta-color and the CB, KC etc. Cheap and nasty.

DaveWM
09-05-2012, 09:17 PM
looking good, color is back, decent gray scale. I do have my old friend line pairing rearing its ugly self. My 1st attempt to resolve that was of course adj vert hold, but it jumps in and out of pairing so I will pull the chassis and start with those brown drops in the vert circuit, esp the boost filter cap (.1 1kv) that sits right next to a compactron. while I have it out I will also replace those pesky feed back caps in the vert plate circuit (.0082 is on of them). I will also replace that .001 on the vert primary to ground, just in case some horz is getting in thru the yoke into the vert out trans. I recall having a real tough dog with line pairing that was cured with a new yoke.

the horz prob needs a bit of work as well, its pretty much all the way to one side to lock and will not flop, so I am going to look at the caps/resistors in that circuit as well.

DaveWM
09-08-2012, 12:17 PM
argh, pulled the sync sep tube with the set on to replace and see if my line pairing goes away. Well it did as did the video. Being a compacton it is a multifunction tube, I know better to pull tubes with the set on, but I did it anyway and smoked the video driver TRANSISTOR (the only one in the set). Of course there was no actual smoke just a blanked out screen. I had anohter Si NPN handy so popped that back in and all well.

So warning becareful about pulling tubes alway have power off just to be safe.

Will try to see if I can get the CRT out an pop the cat off next.

Electronic M
09-08-2012, 01:39 PM
Tip when dealing with multi-section tubes: if you have many spares handy cut off or bend the pins on the section you want to disable and make sure to plug it in the right way...I've done it that way before and it works.

DaveWM
09-08-2012, 03:43 PM
popped the cat, did not have to soak as the PVA was soft enough to dig out spaces for the wood wedges (clothespins), about 10 in total. Just have clean it, put it all back together and will call it done. This set has a near mint cabinet, but the CRT red is a bit weak but not bad. After I get it all together I think I will get started on that CTC-5. I put a little restore finish on the 5 and it looks pretty good. Has some nicks and chunks missing down near the legs, but the overall finish is not bad.

Tony V
09-08-2012, 05:10 PM
How about some pics :)

DaveWM
09-08-2012, 07:28 PM
will get pics as soon as I get it all back together. CRT is back in, setup the HV/purity. Still need to check the HOT cathode current (did it when I 1st got it but will check one more time). I noticed some arcing down on the pwr board around the varistor, Not sure what that was all about. guess I need to pull the chassis again and check the solder joints. The horz has some thing odd going on, I will get wiggles in vert lines sometimes, not others. Tried adj AGC no help (it works it just does not eliminate the problem). I may need to scope the sync pulse and look at it when the problem show so see if the issue is at the sync or after. What bothers me is its not constant just some scenes with vert lines will get the wiggles while other times not. I have a feeling its some video getting past the sync sep tube.

DaveWM
09-08-2012, 11:20 PM
the cap across the osc coil tested a bet leaky and weak, so I replace it as well a .0047 paper in ceramic tube cap. put it all back, arcing gone on variester, hmm no pic, very dark pic,AGC barely does anything, poor sync lock, WTF....

I looked around where I had just checked some resistors in the sync sep circuit where I had to take them out of circuit (PCB), careful looking shows very small solder bridge right around where I was working. Cleared that out but its getting late so I am just going to call it quits for tonight. I am starting to dislike this set
:no:

DaveWM
09-09-2012, 11:34 AM
well that was it, the solder bridge must have been fouling the AGC. the new cap seems to have made the horz osc a tiny bit better as far as the ability to hold lock with the horz control. Still seems to have that problem with hard vertical lines, so think I will try a couple more things tube wise, then the scope and if that does not do it I will just pack it up and forget it.

DaveWM
09-09-2012, 02:59 PM
don't know what the deal was with the horz pulling, I put the DVD box on it rather than the OTA from a modulator and it seems fine now. the line pairing is settling down as well. I will get some pics soon now, just have to take a break, too hot out in the garage. I decided to leave the brightner off, it has a better pic with it but not too bad with out. Plus I could not for the life of me figure out a good place to put it. I tried zip tie under the CRT neck but then the bump out would not fit. There was just no good place for it.

AiboPet
09-09-2012, 05:15 PM
Make sure your source INTO the Blonder Tongue (or whatever)...is getting a good connection with decent RCA cables. I sometimes have to pay attention that the inputs to my little transmitter are not picking up hum bars from all the other stupid stuff I have in the same cabinet. I used to get all worried I was having filter problems in one of the sets....only to find out I was having issues with the source material.

I know it seems a bit elementary....but I've overlooked this a couple times before and JUMPED to the "worst case" conclussion.

DaveWM
09-09-2012, 07:05 PM
pic is better than this, the motion added some bluriness

DaveWM
09-10-2012, 01:50 PM
Under the heading of not leaving well enough alone, I was thinking about the horz eff coil setting last nite. the fact that the dip took place with a large bit of the slug out of the coil (I did drive it down it never got better) I got to thinking maybe one of the 3 caps that connect across the coil may be bad. I checked the .0022 that connect directly across it on the board, but I never checked the two .068 that are connected below the chassis. So even though I have it all back together I think I must pull it out again and check those. I generally just clip on lead, test, and then use a pig tail to reconnect if ok.

DaveWM
09-14-2012, 02:54 PM
I have a slight purity issue on the bottom, tends toward greenish, I think its the yoke as it droops quite a bit due to plastic fatigue. here is a better pic with flesh tones. I ended up going without the brightner.

wkand
09-14-2012, 04:58 PM
Really nice job with this set, Dave. Very patient troubleshooting! I did not especially care for the screen image of Arizona beating my Seahawks, though! LOL!!

Very Nice set!!

DaveWM
09-14-2012, 05:23 PM
Thanks, it was fun. I never got the eff coil figured out (why it has to be so far out for the dip) I checked the caps that are tied to it thinking something was wrong there, but they all checked out. I have some other yokes that I could use to see if I could improve the purity but its not that bad and its hot out in the garage so I will give it a rest. Besides the CTC-5 I have a very nice sylvania roundie console that needs to have the lens popped off (its good to go besides that). So I have others that need attention as well.

DaveWM
09-14-2012, 09:50 PM
I putzed around with the purity a bit, the red blob was just a touch off center so I recentered and then reset the yoke, seems better now (green on the bottom is pretty much gone).

DaveWM
12-09-2012, 06:44 PM
its been a while so I decided to fire this one up again. The tint range is not very effective, the flesh tones don't really change much, the greens go from weak green to weak blue but not by much. the Tint also seems to cause the color to intensify in one direction, like its change the amplitude of the reference as well as the phase. I was thinking of putting my scope on it to see, but I would rather just use my vector scope, but I have it in storage so will have to put that off. I would like to see if the tint control is increasing the petals as well as rotating them.

This set has the pot for a tint control, so it uses a variactor diode, rather than just a variable cap for tint.

any one have any exp with variactor diodes as far as failure modes? that is do they ever become less effective with age and use or is it an all or nothing kind of thing?

timmy
12-10-2012, 09:45 AM
I have a slight purity issue on the bottom, tends toward greenish, I think its the yoke as it droops quite a bit due to plastic fatigue. here is a better pic with flesh tones. I ended up going without the brightner. with the yoke drooping i use flat card board at the end of the yoke and this cures that and it dont conduct emf.:D

DaveWM
02-15-2013, 06:58 PM
finally got the vectorscope on this, and again while it can produce ok face tones the green just was not there. the vectorscope showed what looked like the petals laying down sideways, I tweaked the transformer in the phasing circuit and after about 3/4 turn the flower stood upright and bingo nice greens.

I hint that something is not right is when you get decent flesh tones, yet the tint control does not do much in the way of adjusting.

don't settle for brownish greens, and don't go nuts trying to improve greens with drive and background controls. I will get the Wiz of Oz on it later for a nice screen shot.

DaveWM
02-15-2013, 09:38 PM
here are some shots with the green (and tint) working now..

old_tv_nut
02-15-2013, 10:29 PM
Pretty nice!

DaveWM
02-15-2013, 10:32 PM
"good enough" :D

Zenith26kc20
02-18-2013, 09:16 AM
I don't think GE's looked that good from the factory! I'm jealous!
Great job!
Now I want to watch "War of the Worlds" on it. The Gene Barry version!:D

Zenith26kc20
02-19-2013, 08:41 AM
That picture had me thinking all night! What Vectorscope do you use?
I have an antique Lectrotech V-7.
I even pulled a KE schematic out and remembered how much fun some GE's were to work on!
Again, great job!

DaveWM
02-19-2013, 10:01 AM
Heath kit. got it off ebay, just needed to reseat some of the IC's to get it working. There is a pretty simple setup per the GE service manual, just using the color bar gen and a VTVM. A single test point and tweak coils for max and min, but I did not do that, but rather just diddled the two coils to get the best image on the scope

kvflyer
02-19-2013, 08:44 PM
I too got a Heathkit vectorscope from the auction site. It came with the manual and I have not used it yet. I got it for the minimum bid of something like $10.00 plus very little shipping. I could not pass up the item for that price even if it sits on the shelf. I would guarantee that it was almost never used (if ever used!).

DaveWM
02-20-2013, 10:03 AM
they are fun to play with, have a built in dot/cross/grey scale/purity setting, and shorting switches for the grids. the main thing is it give you a quick check of the output from the chroma demodulators, so if they are not right you don't have to spend anytime messing with CRT setup trying to fix problems that are not real.

DaveWM
03-08-2013, 03:11 PM
had a little set back, fly got hot, started to lose sweep and HV, turned it off, fly very hot.

checking a few things, the line voltage is high (125vac) and I did not yet switch to the high line tap, so that will be 1st. double checked the HOtube, about 215ma, at 115vac its about 200ma, playing with different 6JS6s got it down to about 195ma @115vac.

the eff coils slug is way high (mostly out of the form) to get a dip. I am going to replace the cap and maybe the coil associated with that circuit. and will replace the boost filter caps as well (if I did not to that already).

the service manual has a not about changing the HOtube screen resistor to 18k from 13k so will do that as well.

there is a diode that is connected to the aux winding on the bottom of the fly (agc/burst/hor afc... winding) thru a cap. the neg of the diode connects to the grid of the HO tube thru a 1.5meg resistor.

My guess is this is a safety circuit that cuts off the HOtube in case of hv runaway, sort of like the RCAs that use the neg voltage from the blanker tube as a safety in the same way. Besides the diode there is a cap and a couple resistors. The grid bias of the HOtube was a bit high (too low a neg) by about 10v (was -56vdc vs -67vdc) could be the vtvm calibration I suppose but that is big enough to look into. I will have to get the scope out to be sure. The scope is the only way to see if the neg bias is correct when that backup safety circuit is used (the neg reading is a composite of the two, the rectified drive from the horz osc and the rectified drive from either the diode mentioned above or the blanker tube).

DaveWM
03-08-2013, 08:04 PM
nothing definitive, the horz osc plate load resistor had drifted up some to 92k shb 82k not much but then again, maybe just a tad less drive. While I was in there I went ahead and replaced the .01 coupling cap, it was a small brown drop rated at 400v, it sees a pretty good sized pulse so I put in a .01 1kv dipped. those boost caps are all disc, I really doubt they are leaky, and they had the spark gap cardboard spacer on the lead that I did not want too fuss with.

the diode used in the bias circuit of the HO tube tested fine, and the resistors that form a voltage divider (1.5 meg and 12 meg) were right on the money. There is a small 680 pf disc cap that supplies them from the flyback, it looked fine I just can see it being bad, will leave it for now.

did switch to the HV tap, so before doing anything else will see what it looks like now (couple cap,plate load resistor, and PWR Xformer tap).

I still don't like the looks of the eff coil slug being up so high, but I dont like to make too many changes at once without testing.

Oh forgot the 18k I will have to get one of those from the surplus store tomorrow, I want to to that before testing again as the service man said that should always be replaced.

DaveWM
03-08-2013, 09:18 PM
found a sams on it (I was working from the service manual) so started with the resistance chart on the horz osc, hmmm another plate load resistor off a good bit, this time a 12k that was down to 8.8k. found a 12k that tested 13k in my stash of 2 watt carbons so I put that in. It also called shows a cathode current of 215ma, which is where I was, just seems a tad high.

I am starting to wonder if something in the HOTube started to short or get gassy or some other failure that may have pushed it over the top when the melt down started. oh well anyway press on and see what happens.

DaveWM
03-08-2013, 10:23 PM
I put a 3.3k power resistor in series with the existing 12k, put it all back and touched up the eff coil again, now its about 187ma had to switch to the strong HOtube as the weak one resulted in too narrow a sweep (and about 165ma).

I have to double check the HV and make sure it regulating, the color seemed a bit off and the pic was not as good. I suspect my HV is down. If so I will undo the screen resistor change and check again.

DaveWM
03-08-2013, 10:52 PM
HV holding right at 25kv regardless of brightness or scene changes. The tint is a bit odd, it seems to change a bit from left to right. I suspect its the odd ball GE color circuit (no color osc). Maybe the lower voltage from the tap is effecting it, but I did not notice it on lower line voltage. hmmm have to look at the schematic some more. Maybe a weak burst amp or something like that.

The eff coil is still WAY out nearly out of the form to get the peak. I did not change those caps (the one across the coil and two that go to ground from each end of the coil).

I noticed a very slight foldover on the right edge that was not there before. I was going to adj the coil just a bit to see if I could correct that.

Oh one more thing, the HOtube grid voltage is now about -64v increased the neg voltage about 8v.

what I may end up doing is wiring up the chassis so I can switch out the extra resistance on the screen. I would like to add a low/high switch on the back, I have this on some of my sylvania sets (for the PWR xfromer tap).

DaveWM
03-09-2013, 06:59 PM
after a considerable about of futzing with it, I decided to return the tap to the orig spot, this will boost the overall voltage, which should help the CRT as its only ok. I will leave the screen dropping resistor in place. I think this will get me to about 195-200ma and temps in the 120-140 range once the fly cage is closed back up. the only other thing I did after the screen and those couple of plate load resistors and the coupling cap for the HO tube as to replace the .47 filter cap on the AGC, the old one way cracked around the terminals, not sure how that happened, but I figured it may have compromised the seal.

I plan to try a new lin coil in it at some point to see if that has any effect but that will be a later day. I really want to get back on that CTC-7AA

DaveWM
03-10-2013, 01:48 PM
so I am putzing around with it somemore and I notice the horz scan lines have a slight wiggle in the last couple of inches on the far right side. Damn...

keep looking at it, try a new H osc tube, reset the horz osc coil (ground the test point a set for float by), no sine wave coil on the GE to fool with. still there.

get scope, has a funny looking bump on the flat top, but that may just be the scope picking something up. looking at the set in the mirror hmmm.

Take a break, start up the movie again, odd some french words (part of the movie warnings are in french for some reason), any way I did not know the french read from right to left, its been a while since I took french in HS but I do not remember that...

next come the Brothers Warner imblem, wait thats supposed tot be WB not BW..

Duh horz yoke hooked up backwards. all the time I was looking in the mirror and it looked right. I reverse the horz leads on the yoke and the little squiggle is gone. Sometimes the easy stuff will get you.

I am going to put it away now before I break something. The HO tube is at 195ma so I hope my overheating fly is done. I will get a new lin coil and replace that later to see if that makes the lin adjustment point more reasonable looking, but I have had my fill of this one for a while.

ChrisW6ATV
03-12-2013, 11:18 PM
Dave, I had to laugh at the backwards yoke that was OK in the mirror! Thanks, we all make silly mistakes from time to time.