Can someone please give a roundabout idea what temperature (in Farenheight) that an average 60s color set should produce when healthy. My set is the 64-65 Zenith, but I am making this separate thread and hoping that we can be non brand specific.

This way I hope future vintage radio & TV people will have a reference to what is an important and most often talked about topic. I have just never seen a specific temperature range for this. Certainly it will be a range due to the many variables involved, but it would be good to know more than if the wax is not melting off, or if it's not smoking then it's OK.

With today's myriad of cheap electronic devices to play with like a laser thermometer, it will be really easy to monitor this.

Wow, I'm surprised at no feedback on this one! I saw a YouTube video once where the guy is checking his with a laser, but he never said what range of temps would be acceptable.

I think its more a measure of cathode current through the horizontal output tube that is important. If the current is right, the picture is the correct size, no yoke problems, then you can make a temperature measurement and that will be the temp. Also picture tube current should be correct.

Don't forget it's the current draw on the transformer that generates the heat......

And on the primary side it's the drive current through the winding.....

OK, that helps since I have already been through the cathode current measurement and come out just a little above 200mA after installing a replacement for a broken horizontal efficiency coil.


Frankly I was a bit surprised at how little difference a lot of turns of the slug of that coil makes. I figured that in tweaking it I would see a vast difference, but not really that much.

It should make a big difference, have you checked the cap (or caps) across it? You should see a fairly sharp tune range (again with a subjective statement).

The prob with temp input is there are so many variables, ambient temp, line voltage, horz out emmisions, and then there is the lack of consistent measurement (kinda hot, slightly warm, barely warm,hot, very hot) so it becomes very subjective.

I generally use a LED targeted IR gun, aim for the hottest spot (often the point near the output lead to the HV rectifier).

I don't think polling peeps is going to get much good info due to all of the above.

That being said I personally think that if you were going to use a tube type tv with an RCA style fly, then active cooling would be in order as most of my RCA and clones get too hot for me to leave them running for hours on end.

a small muffin fan that moves the air around the fly makes a HUGE difference.
consider that the FLYs can not be easy to get AND they are 50+ years old make me think this is a good idea. And NEVER leave on unattended. The down side to a fan is IF they were to catch fire you would have a blow torch on your hands.

Dave is right that coil should have a peak, and if I remember right, you tune it for minimum cathode current.....
There should be a number in your manual....

I generally go by the bath water standard for flybacks if it's hotter than you want your bath water to be then odds are there is something that needs further work...If I plan to run a set all the time I do tend to try for cooler operation though.

Power supply transformers on the other hand are sometimes MEANT to get hotter.

fyi, I noticed you said you have a zenith, I am not positive on this, but IIRC a lot of those did not even have a eff coil. Zeniths seem to have a lot less issues with flyback. If you give me the chassis/model I can look at it.

It should make a big difference, have you checked the cap (or caps) across it?

I replaced the single cap across it when I installed it. I hope that I didn't connect it across the wrong lead. There were three and I wasn't working in the best light or position unfortunately. I would think that if I hooked up to the wrong lead that I would see some fairly major indication of it. I hope so anyway. Guess I'll get out the schematic and double check that.

fyi, I noticed you said you have a zenith, I am not positive on this, but IIRC a lot of those did not even have a eff coil. Zeniths seem to have a lot less issues with flyback. If you give me the chassis/model I can look at it.

Yes, it's a model 5111 and most certainly has the efficiency coil. It's stamped in the chassis and I have ordered and replaced it. Anyway, the Sam's folder that I have says that it is a 25LC30/U chassis. It's Sam's Set 722 Folder 4 if that helps. It will come in handy to see if I have the single cap hooked up wrong.

Dave is right that coil should have a peak, and if I remember right, you tune it for minimum cathode current.....
There should be a number in your manual....

Well, about 200mA seems to be the generally accepted in the realm of this vintage of color television from what I can tell. Now, what I don't know is about what kind of peak I should be seeing with this measurement. First I want to say that I am using a Simpson 260 and I use the 50 volt scale. So unless there is a big variation that I would see here a difference in say 100mA isn't going to look like a lot of deflection of the pointer.

To be specific, the lowest point which was around 200mA is as low as it goes and it doesn't go way high from there. Now I have noticed that the slope is pretty sharp in that it doesn't take much of a turn to make the difference. Really, this is probably a good thing as I wouldn't think that you would want the potential for some way high, possibly damaging amount of current to flow, and of course if it were way to low there would be other issues.

My thoughts of possibly botching the install of the .15mfd cap look to be wrong. The schematic shows (as well as the old unit I removed) the cap across the two outermost terminals, and it is. So the only thing I think that I could botch would be mixing the conductors up, so I checked to make sure that #2 terminal which is a center tap, was connected to a .1mfd which it is. The other two leads I think could be swapped and it wouldn't matter since they are both across the 1 ohm winding.

I have a good raster which is linear both vertically and horizontally. The only battle right now is the hissing of I guess corona arc inside the HV cage which causes interference in the picture. I just know that flys are very critical with these sets and being transformers we all know that we don't want them running too hot, so I thought that I would try to get an idea of a reasonable temperature and HOPING that the arc or whatnot is not somehow internal to the fly if that is even possible. I am not familiar with the symptoms of shorts or other conditions that may occur with flys.

Still trying to get the corona arc out of this set and to make a long story short I changed the H. Output tube and damper. Then I hooked up my Simpson 260 to the cathode circuit and the set now initially holds about 200mA, but after several minutes builds up to about 250mA which I think is critical if not dangerous to the fly.

I should have just recapped this set, but I wanted to repair it first and see what I have, then consider a full or partial recap. Can someone advise me on what would cause this climb in cathode current and am I going to fry the flyback. It does seem to be running hotter, but not too hot to touch or anything. The darned brand new efficiency coil that seemed to be the only one in the country that I could buy seems to be frozen already! Can't understand that one. It was n.o.s. by Thordarson. I tried turning it from the rear and a chunk of the slug fell out. Geez!

Might have to sell this one to one of the "roundie" pros here!

Aw jeez that is a bummer. Coupla questions..

Did you still get the initial 200ma reading after the eff. coil slug broke?

When the K current climbs to 250ma, what does the raster look like?

Gassy H output tube could be the cause of excessive current (since it starts out normal, then climbs).
Definitely don't run it like that, since it's hard on the fly.

I should have just recapped this set, but I wanted to repair it first and see what I have, then consider a full or partial recap. Can someone advise me on what would cause this climb in cathode current and am I going to fry the flyback.


:) Hi Tubeguy ,

Any time I've encountered runaway cathode current , it has always been found to be either the grid circuit capacitors failing and driving the grid positive or a bad tube as old coot suggested . I've seen both gassy and tubes that have developed "secondary grid emission" do the runaway cathode current thing , but mostly find it in the capacitors slowly going partially shorted .

:) Hi Tubeguy ,

Any time I've encountered runaway cathode current , it has always been found to be either the grid circuit capacitors failing and driving the grid positive or a bad tube as old coot suggested . I've seen both gassy and tubes that have developed "secondary grid emission" do the runaway cathode current thing , but mostly find it in the capacitors slowly going partially shorted .

I was going with a gassy tube since he said it starts out normal at 200ma then climbs gradually. Whereas a leaky grid coupling cap woulda put the current high immediately.

But that cap should always be replaced as a matter of course anyway. Same goes for the grid coupling cap feeding any power stage (audio output, vert. output).

Aw jeez that is a bummer. Coupla questions..

Did you still get the initial 200ma reading after the eff. coil slug broke?

When the K current climbs to 250ma, what does the raster look like?

Gassy H output tube could be the cause of excessive current (since it starts out normal, then climbs).
Definitely don't run it like that, since it's hard on the fly.

OK, I am going to try to answer all questions based on this initial quote. I did get about the same readings after the slug broke. Just a chunk fell out of the back side under the chassis. The raster to me seems fine, but remember all along I have had barkhousen lines or some horizontal interference along with the distortions of the corona arching which I could never pinpoint, but sounds like it is inside of the HV rectifier. Oddly, when I did this check I had the polarity wrong on the meter, so I switched it to -DC. That was a mistake; probably a dumb one. The movement went the right way, but I did get a bit of a smell of something burning. Switched the wires, went to +DC and the arching was gone; just the runaway current....

I did save the old slug from the coil with the broken spool, but I can't get the new one to move at all and I fear it falling into a bunch of pieces and then finding out that the old slug is a different size of something. I don't know why that thing froze that fast except for possibly the coating on the windings heating up and gluing it in place. This set is driving me crazy....

I once brok a slug because I was being an idiot and using a metal hex key (BIG nono :nono:) instead of a plastic diddle stick. Slugs can be replaced with ones of similar dimensions from other parts coils/sets as long as the threads of the inductor are not shot. It might be a good idea to look into a plastic safe lubricant for them...

EDIT:One thing that might loosen your slug is (provided the wire is thick enough to stand the current) with the set turned off connect a D cell battery across the coil and let it warm up until the slug loosens up, then remove the battery and the slug and then quickly try to clean any wax or other gunk from the slug and coil threads before it cools....IIRC I did that to free the frozen lin. slug on my CTC4.

I may have to try that. The coil has three terminals as it is center tapped. I hate to, but I assume that I would connect the D cell to the outside terminals. Makes sense I suppose. If my old original slug is the same dimension as the Thordarson "direct" replacement then I am in business.

However, I tried adjusting after the current went high, so there may not be a reason to further try to turn the slug that was dipped to 200mA to begin with. Perhaps, and worse case scenario I will be able to find someone with a spare Zenith chassis that would sell me one, but I had zero luck with that before. Maybe this is why everyone has RCAs. Stick with what everyone has so you have resources for parts. I like Zenith and it's really amazing that the set works to the degree that it does being that old and dormant for several decades.

There are plenty of folks on this forum that have one or more Zenith roundys (my self included). The reason you don't see a ton of repair threads on Zeniths is that they are a lot more stable once working than RCA based sets (I also own some RCA based sets, and can tell you that the PCBs are a perpetual source of intermittents)....Heck a number of Zeniths that I own are still going on all original parts save for tube replacements.

Yeah, they are supposed to be really great sets, as you said once working. I'm going to try to keep fighting that battle. I wish I could get that slug to move just one more time and slide the old one in there. Seems like they would be the same size one being a replacement part.

The thing was free as a bird just a few months ago. It doesn't seem to run hot, but does look like it has at some point as there is what looks like melted laminant that has run what would be down if the set were sitting upright, but it has been on it's side since I put that thing in. I'd give every N.O.S. vintage flyback and yoke I have for a couple of extra coils and maybe a spare fly just in case.

EDIT:One thing that might loosen your slug is (provided the wire is thick enough to stand the current) with the set turned off connect a D cell battery across the coil and let it warm up until the slug loosens up, then remove the battery and the slug and then quickly try to clean any wax or other gunk from the slug and coil threads before it cools...

I still may try this as I would like an intact slug in my new coil, but the other half of me says leave it alone; for now at least. I have actually ended up with some better results then where I was heading earlier. I thoroughly cleaned the cup that the HV rectifier sits in and eliminated (for now at least) the corona arc and resultant interference that it presents to the raster.

Also, I took out the regulator tube that I had put in the night I checked the cathode current as well as the H.O. tube and put back what had been in there before. I didn't really have a reason to change the H.O. tube other than to try to get rid of the barkhausen interference lines ever present on both sides of the raster. Most prominent on the right side which I think is covered more by the damper tube. I may be wrong in these statements and welcome correction. I say barkhausen lines meaning a light line that once was straight but now is twisted like a snake. Sort of like the horizontal hold is about to let go although it is stable.

The regulator tube was just one of two that I had that tested better on emissions and no gas. However, when I pulled it I noticed that there is a sort of a ring that you see on I believe the would be the plate or the upper portion. The dark coloring of that ring is gone and is copper colored as if some arching has gone on in whatever set it came out of. It is not from use in my set. I just picked it up in a box of tubes at the flea market. Even though this tube had a better emission, it has a shorter life test on my Hickok 6000A. At any rate my H.O. cathode current stayed around 200mA as long as I ran the set as opposed to the runaway current that I mentioned previously. I still don't know how it will perform over a long period of time, but I will find out and post.

Again, the coil would naturally be better intact and able to be dipped, but I certainly don't want to further damage it as I have absolutely no leads on another. I don't see why they are so hard to find; at least second hand. As far as heating it up with a battery goes I am afraid that I may short the windings by burning away the laminate. At least I had adjusted it before it froze up and being new I fear that the only way that it could freeze up was that it was somehow overheated and the insulation that melted is holding it in place. As long as it isn't shorted I am ok and I have the spec sheet resistance values.

Thanks so much for the tips everyone!

One thing that might loosen your slug is (provided the wire is thick enough to stand the current) with the set turned off connect a D cell battery across the coil and let it warm up until the slug loosens up, then remove the battery and the slug and then quickly try to clean any wax or other gunk from the slug and coil threads before it cools.....

I still may try this as I would like an intact slug in my new coil, but the other half of me says leave it alone; for now at least.
...
As far as heating it up with a battery goes I am afraid that I may short the windings by burning away the laminate. At least I had adjusted it before it froze up and being new I fear that the only way that it could freeze up was that it was somehow overheated and the insulation that melted is holding it in place. As long as it isn't shorted I am ok and I have the spec sheet resistance values.

Can't you just lightly warm it up with a hair drier or heat gun wafted around the area or something so it's less likely to harm a winding trying to use it as a heating element?

Can't you just lightly warm it up with a hair drier or heat gun wafted around the area or something so it's less likely to harm a winding trying to use it as a heating element?

That is exactly what I was thinking. If a hair dryer will do it, that would be the thing to use. A heat gun puts out an incredible amount of heat and I fear that it would melt the spool which takes me all the way back to my original hunt for one of these. My spool had deteriorated to dust and the winding was just dangling. That may have been OK really as the slug was in there and the bulk of the winding was just as it would be with the spool, but the dangling winding's weight caused some separation of the winding and I was advised that just that would be enough to render the part bad.

I should have (back then) checked the H.O. cathode current while moving the winding around a bit to see what it would do.

OOPs! Duplicate post.

If the K current is holding reliably at 200ma., i would be inclined to not fuss with the eff. coil any more (despite not having been able to find the 'dip' earlier).
Back in the day, 210ma. when 'on dip' was considered nominal.
200 would have been all the better.

Thanks and I am inclined to think the same as (correct me if wrong) if the set is holding for let's say 30min. at 200 or 210mA and then I once again see a rise, it's not going to be the coil causing the rise and adjustment would not rectify the problem. I hope my thinking is right on this. That way I can move on to getting the video back to being clear and the color working once again.

I get so frustrated because at first this set played so beautifully and then the bottom fell out. First loss of color which has reemerged a time or two, followed by a pretty nasty picture. I'll have to post some pics I took of it playing the Woodstock movie. I WILL get it back to that state; 'with a little help from my friends.'

Thanks and I am inclined to think the same as (correct me if wrong) if the set is holding for let's say 30min. at 200 or 210mA and then I once again see a rise, it's not going to be the coil causing the rise and adjustment would not rectify the problem. I hope my thinking is right on this.
I would agree with that approach.
In addition, i would consider putting a #44 bulb in series with the plate of the H out tube. It's rated at 250 ma at full brilliance, so it'll run a little dimmer and oranger at 200 ma. Thus any brightening will give a visual alert of current rise.
Either that or keep a milliameter in the cathode leg.

Either that or keep a milliameter in the cathode leg.

With that thought in mind, or perhaps fusing the circuit; I simply broke the cathode leg and soldered in two strands of wire long enough to reach well outside the chassis. So far I have no permanent mounting and not sure what I will do there. No big deal, but it is really convenient to be able to wire in my Simpson 260 for these checks. When I'm done I just throw on a wire nut and go about my business.
I used stranded wire as that is what I had on hand. I think in the present case of the wires moving around a bit and for future routing purposes that stranded was the right decision.

I hadn't thought of using a bulb really. Sounds like a good idea if you know the nature of the bulb meaning what it would look like at it's brightest lumination and 'normal'. It would look a bit raggedy, but you could simply have it dangling under the set to be observed while watching the set. For that matter I guess you could put it in the tuner indicator! LOL

For comparison, the bulb's 'normal' is at its rated 6.3V (/ 250ma.).

The bulb would need to be located physically at the plate cap, because there's several thousand volts of pulse there. Running wires around would introduce an arcing hazard.

The alternative would be the cathode leg since there's no arcing hazard and you can run wires around with no problem.
But in the K leg, the bulb will introduce a few volts of negative grid bias plus a bit of negative signal feedback. This will reduce the gain a bit, which may or may not be a problem.
The feedback can be cut by bypassing the bulb with an electrolytic (maybe 1000 uf @ 10V.).

Of course a milliameter in the K leg would be ideal since it's essentially a short and would need no bypassing.

Mr. Coot, I must stop for a moment here and say thanks so much for reading into what is only limited information and trying to help someone sort out a situation like this. I am often amazed at the amazing amount of information retained and conveyed through people like you who I can only assume must have been lucky enough to work in the electronics field when it was what I refer to as real electronics.

As a student of the discipline myself I have often felt cut short by what has in many ways become a dumbed down craft both in education and in "the field." A lot of it has to do with the throw away society that we have evolved into that simply leaves no place to exercise the kind of knowledge that was once almost commonplace. I could go on and on in a rant here, but I work every day around "techs" who can't even read an analog meter. If they understood what they are looking at, they wouldn't understand how to use multipliers. There are those who by the grace of God know AC from DC, but really just the terms more than what they really are based on electron theory along with the fairly rudimentary understanding of the sinusoidal wave and how it can be altered to create the later. They don't have a need to know for one thing I guess to give them credit. It truly is a plug and play world now and I can't say enough in thanks to those who help pass the torch of what could become a lost art. Certainly, were a long way from vintage color TVs and such, but I truly believe that it takes a vast understanding of electronics to be successful at doing what we do here at VK and other places like it. I think the common Radio and TV repairman of yesteryear would bear the same or more knowledge than that of someone with a graduate degree these days.

Back in the day, 210ma. when 'on dip' was considered nominal.
200 would have been all the better.

Finally had some time to sort things out a bit better and made some improvement. First, the set is holding a steady 210mA, or did for at least an hour. The corona arc is all but gone, but you can sometimes hear it hiss just a bit, but not showing up on the screen. I'm real happy with that, but I would like to have it completely clear of any corona discharge. Possibly some more extended play time will work that out.

Either earlier here and/or on another related thread I mentioned complete loss of color. I have read that 6GH8 tubes were troublesome for whatever reason. That must have been an understatement as I remember checking the single tube in my set's compliment (which acts as the chroma reference oscillator) a while back and it checked OK, but I can't remember if that test was done on my cheaper Accurate Instruments tester or on my Hickok 6000A.

Either way it goes, I pulled the tube tonight and plugged it into my Hickok and the tube was really weak (in the red) on both the triode and the pentode tests. Luckily I had about 8 of them in my used collection and of them all only one came up to the question mark symbol between the bad and good scale on both tests. I thought that it was a bit odd that most of the tubes I had were testing in a very similar range which fell within that ever present "diodes OK" area, I tossed any that were below that point until perhaps I just try them in the set.

The one that was dead in the middle (question mark) got put in the set and BAM color at long last! :banana: That's been a long time coming as it's was the first thing to go wrong with the set. Now if I can get that ugly white line (Barkhausen?) out of the left side of the picture and do some convergence work I might be one of those lucky guys who have Zenith color sets that they don't have to post about because they work as is! LOL! :D I'll have to find me a CTC something to keep me busy if this goes right. I really don't have time anymore for a proper recap if repair is all that is needed. We will see.....

If'n yer wanting to experiment on that Barkhausen thing..... I have 2 of the same model set
and they both have OEM Horizontal output tubes still in them, and they both have an ion
trap on them about midpoint on the tube. I got the Sams for the set, and they have the ion trap
on from the factory, and an explination as to why the trap is there.... and yes they
say it's the "B" Barkhausen.

So If you want to, get a small magnet, hold it so you don't get a shock, like tir it to a
wood stick, and move it near the side of the tube and see what happens....

But if it's the tube that the set calls for, and it's a good one, it's possible the problem
is something else.... Like your mini aurora show..... I have found the best thing
to do for that is to clean everything near it with windex, then let it dry for a few days.
And for the slug in plastic coils, chapstick is the best plastic safe lube to use.... It don't
take much, apply with Q-tip inside the coil, then wind the slug in..... Good Luck....

On the other thing.... You should check voltages on the Horizontal output tube, before
and after the shift in current. Do any of them change, even a little... That may be a clue...
Remember bias on G1 to a good degree dictates cathode current..... Is it runaway or not....?
Good thing to look into that screen grid cap as mentioned too....


.

Before reading Username1's post, i was gonna say..
if you don't want to do a recap, at bare minimum replace the coupling cap going to G1 of the H out tube. Then he sed the same thing.
The slightest leakage in that cap will push the grid more positive.

Before reading Username1's post, i was gonna say..
if you don't want to do a recap, at bare minimum replace the coupling cap going to G1 of the H out tube. Then he sed the same thing.
The slightest leakage in that cap will push the grid more positive.


Yup.... There's 2 votes fer checkin the bias on the Horiz. Output tube....

Even if you decide to just change it, check the voltages first. It will possibly be
the only "test" of the cap, just in the small leakage there may be, even if any
possible cap. test itself may never reveal it to be bad, a higher G1 voltage may
be the perfect load test to show it's really bad....

.

But don't just check it; replace it as a matter of course. Same with the coupling cap going to G1 of any power stage (like audio out, vert. out etc.) since power stages are the most vulnerable to overcurrent.

If'n yer wanting to experiment on that Barkhausen thing..... I have 2 of the same model set
and they both have OEM Horizontal output tubes still in them, and they both have an ion
trap on them about midpoint on the tube. I got the Sams for the set, and they have the ion trap
on from the factory, and an explination as to why the trap is there.... and yes they
say it's the "B" Barkhausen.


Remember bias on G1 to a good degree dictates cathode current..... Is it runaway or not....?
Good thing to look into that screen grid cap as mentioned too....

I have heard of the ion trap used in this manner, but there is no reference to one recommended in my Sam's Set 722 Folder #4. My set's chassis is the 25LC30. I wonder if you have the older chassis, or maybe I should say the other chassis that some folks are talking about in another thread. It still may be worth a try.

I like the sound of the Chapstick idea for the slug as long as I can get the old one out. It seems to be disintegrating for whatever reason, so I keep thinking that I should get it out and put in the very much intact slug from the old unit that I removed with disintegrated plastic. On the flip, Old_coot88 suggests leaving it be as it would not be the problem if I had runaway current. It's only a fine tuning to my knowledge. Some earlier mentioned tube swapping caused and re-swapping rectified the runaway current which led me to discover the stuck slug trying to control it in a bit of haste. Right now she is holding a steady 210mA which is supposedly acceptable.

Now, to the G1 capacitor and biasing. I have not yet had time to check any voltages and it sounds like the right thing to do is simply replace such a critical cap. Looking at the schematic I see a .01mfd (C66) to pin 5 of the H.O. tube 6HF5 via a 100 ohm resistor. There is also a .001mfd @ 10% (C65) in parallel to that going through a 33K ohm resistor to ground. Admission of guilt on limited knowledge leads me to ask which of these is the right one. My bet is on the .01mfd going straight to G1, but I want to make sure along with getting a more firm understanding of these circuits.

This is great information once again folks! Thanks so much!

Hi !

I believe I was unclear, I have 2 sets of the same model, but NOT the one you have. What
I mean is that the sets I have are 1958 Emerson B&W tv's and both were made with
a built in problem that required the ion trap on the H Output tube.

Onto the coupling cap. Since you believe you have a current problem, knowing that
you have found the problem part, and actually fixed the problem is the reason you
would want to check voltages Before, and After replacing the coupling cap. on this
issue..... It is a way to learn, and help those who follow this problem on this thread
learn too.... If you just blindly replace the cap, did anything change...? Was a bias
voltage change the reason for the higher current ? Did you fix it or not ?

If the slug in the coil is broken, remove the coil and drill out the broken slug, start
with a drill just a little bigger than the hex opening, then go up from there. Eventually
you will have broken pieces, and have to knock or unscrew them out with steel wire,
or very small drill bits. Unless you can get a new coil and just replace the entire thing.


.

Hi !

I believe I was unclear, I have 2 sets of the same model, but NOT the one you have.

If the slug in the coil is broken, remove the coil and drill out the broken slug, start
with a drill just a little bigger than the hex opening, then go up from there. Eventually
you will have broken pieces, and have to knock or unscrew them out with steel wire,
or very small drill bits. Unless you can get a new coil and just replace the entire thing.

Yeah, that though me off a bit, but still good information and may actually work, but I bet my Barkhausen line is from something else. The method on the slug is good too, but I am thinking of trying an EZ out to remove the slug. The main thing is not damaging the coil.

I gave some specifics last night on G2 coupling capacitors and what I see in my schematic. Will someone look that information over and give me a short lesson in coupling and which of the two capacitors mentioned would be the coupling cap. Again, the one that goes straight from tube to tube would be the logical choice, but I could easily be wrong. Being that they are both in this critical circuit, it would be smart to get rid of them both. I will have to see what type they are to pass some judgement. There are actually two or three "bumblebee" caps in this set that I know need to go. I think the black beauties have a bad reputation as well. There was one of those across the windings of my old efficiency coil. The old brown 'drops' are probably the best as they are not paper/foil like the others.

Now, to the G1 capacitor and biasing. I have not yet had time to check any voltages and it sounds like the right thing to do is simply replace such a critical cap. Looking at the schematic I see a .01mfd (C66) to pin 5 of the H.O. tube 6HF5 via a 100 ohm resistor. There is also a .001mfd @ 10% (C65) in parallel to that going through a 33K ohm resistor to ground. Admission of guilt on limited knowledge leads me to ask which of these is the right one. My bet is on the .01mfd going straight to G1, but I want to make sure along with
It is difficult to tell from the above description how the 2 caps are actually wired... if the .001/33k resistor combination connects to ground, it would seem to *not* be connected in parallel with the .01/100 ohm combo. The coupling cap would be located between the plate circuit of the horizontal oscillator and the grid of the horizontal output. If the other cap is also connected somewhere in the grid circuit of the horizontal output, I would replace it as well.

jr

This is a typical coupling capacitor used between stages. It's the AC signal
path from the output (plate) of a previous stage, to the input (grid) of the
following stage. Not all configurations are the same, it is easiest to spot if
you are following the AC signal path, as a job of the coupling capacitor, is to
pass the amplified signal to the next stage, but block the DC voltage from the
plate, or collector circuit if it's a transistor amplifier. And again some configurations
will be different.

In the IF sections of your tv coupling between stages is done with a coupling transformer,
there is a load resistor after the transformer, but the transformer passes only the changing
signal amplitude from one side, to the other side, so again DC is blocked.

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Thanks a lot "Squirrel Boy" for the fine explanation and pictorial. The two definitely give me a better understanding of the circuit and will allow a clearer explanation of what I see in my schematic.

My .01mfd certainly goes from the plate of the horizontal oscillator to the grid of the output tube same as C85 in Username1's pic. So that is the true representation of a coupling cap. The .001mfd going through the 33Kohm resistor is positioned just as C84 is in Username1's pic only there is a ground symbol at the end. That pretty much has them in parallel. In the picture a load resistor is pointed out. Mine seems to be a 2 watt 82Kohm unit. Finally the picture shows an R127 going to chassis ground. There I have a 10Meg.

This may be a useless comparison to some folks, but it is helping me a lot in learning and that's often what we are here for. Parts swapping is more or less taking the low road. Not that it's all I know, but I am often guilty of it. I want to start using my oscilloscope more than I do. I know "TV repairmen" who seldom if ever use one, but it is certainly one of the more important tools in the electronics arsenal.

Thanks again everyone and when I make some changes or other accomplishments I will be sure to update.

There are many different tools that you can or need to use at different times
to repair any item, tv car, vacuum. I have found most repairs were actually made
using observation, block diagrams, walking through what was happening in my
mind, using a voltage or ohm meter. Oscilloscope was not too often the first tool
I went to for a lot of troubleshooting.

While looking for examples of coupling capacitors on the internet I was not able to
find a good tube example, so I took that one from a tv. I did find a really really really
good page with some design stuff on it. Now you don't have to do any math to see
what it going on, and you can follow the examples pretty easily, just let it work in....

http://dc213.4shared.com/doc/Te4Wew3A/preview.html

I believe this is a test page for someones website, so it may not be up too long....

I would download it and save it....

.

Interesting link. Unfortunately transistor based, but I guess coupling is coupling, and I did want a better understanding. Thanks!

Transistor Base = Tube Grid
Transistor Collector = Tube Plate
Transistor Emitter = Tube Cathode
For basic NPN transistor.
But tubes are Voltage Amplifiers with near infinite input impedance, and your
basic transistor is a current amplifier.... I think its FETS that are close to tubes
in the respect to no base current. Coupling is coupling as far as signal goes....
because it is amplifier stage to amplifier stage, so its ac signal coupling.
And there are books where you can find the same stuff but with tube examples.
They may just be a little harder to find...

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I like the comparison as I have an understanding of both and many of their capabilities, and I know rudimentary circuit applications for the transistor as our labs in college naturally in modern times were transistor based. I am lucky enough to have gotten my feet wet in a time when we studied both vacuum tube and transistor theory and application along with the God given opportunity to know how to use an analog V.O.M. Seems like our class had Simpson 260s and I don't ever remember digital anything although I know that they existed.

So, somehow I always looked at tube circuits or devices as one thing and solid state as another. So much for hybrids I guess. As far as books I have quite a library of vintage electronics books including a complete 1940s National Radio Institute (N.R.I.) correspondence course textbook set. Only a few of my books come up into the transistor era which never bothered me as my more modern college books cover all of that and of course the digital realm.

So again, thanks for the section by section comparison. Now, I need to find those two caps in my horizontal output circuit and get them replaced along with taking some voltage measurements and get them posted. For now I'm not going to worry with scope waveforms as I think it would really just throw me off track in my true understanding of the circuits and their behavior.