Westinghouse H886K21
 

Hey everyone,

I've come into a 1955 Westinghouse H886K21 which is my first tube TV set. I've done restoration and repair of tube radios and HiFi, but no TVs. Having watched many hours of YouTubers' TV restoration videos I felt foolhardy enough take this on.

I found it with a brightener (which I removed) and roughly 2 out of 3 tubes tested weak and a few with minor shorts. Before pulling the chassis I've first tried replacing tubes to see if I could at least get a baseline. Came up right away with full horizontal, some vertical but no visible image and after replacing a few tubes and working controls free, I was able to get sound, but still no image. There's a low level of constant static in the background of the audio, but otherwise it's full and has good volume so we know front end is functioning. I've also replaced the sync amp, the sync separator, AGC keying, vertical mult, vertical output and horizontal AFC tubes, which has yielded little change.

Here's a video of where it's at:

https://youtu.be/vGhXHNI5qdE

In the video, I'm first adjusting the brightness, then the vertical hold then the horizontal hold (clearly the control needs a good cleaning). Adjusting the rear sync, height, width, linearity, AGC controls affects the height (though never goes below the top half of the screen vertically) but still no solid picture.

As I haven't yet even pulled the chassis I'm obviously not expecting perfection as it's likely on a good amount of original components. I'm more inclined to want to troubleshoot to learn as much as I can, instead of just doing a wholesale/shotgun replacement of caps, etc.

So I guess I'm looking for some advice for where I might start, and next obvious steps to try to sort out my little vertical problem, first?

Thanks!

FK

I hate to be the bearer of bad news, but with a set of that vintage, a shotgunning of the original paper caps is strictly necessary. A set in that state is essentially impossible to troubleshoot as you suggest. There's no video, weak sound, insufficient vertical sweep, horrid hum (though it might be 6BN6 buzz; Westinghouse and Zenith were fond of the 6BN6 in that era). And that's just what we can see that's wrong with the set. You could be running at extremely high horizontal output cathode current thus putting your flyback at risk, etc.

Plan on replacing all the paper caps and electrolytics, but you can do what I do (as suggested by Phil Nelson): replace a handful of paper caps, say six or seven, then plug the set in and make sure you haven't made anything worse.

Start recapping in the sweep sections and power supply first to avoid nuking an unobtainable part.

...and if you need the Sams Photofact, it's Set 294, folder 11. I have an original, yours for postage. PM me if interested.

Well, shucks. Was hoping it'd be like one of those videos where replacing a few tubes and it plays "fairly well". Beginner's luck I suppose!

It's possible the sound issues you mentioned could be caused by the cheap DTV box I was using for that, so if that persists after doing recap I'll try other sources and see.

I've ordered a full set of caps and agree with your technique of recapping in small batches to make it easier to spot and roll back mistakes. The good thing is that this cabinet has a lot of space to work and seems very simple to get the chassis in and out so hopefully this will be a good learning TV!

Thanks for the advice!

FK

Update -- finished replacing paper and electrolytic caps and with a lot of fiddling of the controls, I finally have a picture of sorts.

https://www.youtube.com/watch?v=-nMNRP56N1Y

The vertical hold is very touchy and this is the best I can get for brightness and contrast. As this CRT had a brightener on it when I found it very possible this is the end of the line for the picture tube. Think there are any more gains to be made by working on it, or best to shelf it and start the search for a 21ALP4A? :(

Thanks all!

FK

If it had a brightener on it, it is that dim, and the CRT bias voltages and HV are in spec, then may as well put the brightener back on and see how decent of a pic it can make and for how long.

B&W CRTs prior to ~1960 were often not nearly as bright as newer CRTs we are used to seeing....That said it does look dim for a tube of it's era.

I may have a good spare 21ALP4. IIRC I sold one this spring, and I think I had 2 before then.

Since the vertical is rolling and the horizontal is stable I'd suggest checking the vert and sync separator tubes, checking all resistors in those stages and replacing any that are out of tolerance.

Get the set to working solidly first, then you'll know for sure that it's worth hunting a new CRT.

So with the contrast at about 10%, the CRT voltages are on spec, though there's no picture at all until contrast is past about 90%. The B+ supply voltages are right on too. I don't have a HV test probe though so can't measure the HV unfortunately. I've been checking resistors and only have had to replace two or three, and the worst was maybe 25% off so clearly they used good parts.

Have tried a few different vert, sync and AGC tubes and have the best ones in there now, though there wasn't a huge difference. Both horiz and vertical lock are fairly poor and only get solid horiz lock with the control is the extreme end. It also seems to get worse as the set heats up.

Nothing I've done has improved or changed the brightness. Put the brightener back on for a little bit but improvement was minimal if any. That video was recorded in a pitch black room and it actually seems a bit brighter on the video than in person.

I'm going to keep grinding and checking voltages and components and see what happens.

Thanks for the tips!

FK

That CRT will not be hard to find. The 21ALP4, 21CBP4, 21AUP4, 21BSP4 and others were pretty much used in all the mid-50 sets. I know for sure that Motorola, Silvertone and Philco used them in almost all their 21" models 1956-58.

Can you try a good CRT checker to be sure you can't give it a good bump?

Have you tried adjusting the Ion Trap? A slight misadjustment will kill the brightness.

It could also be low HV... I've seen sets, especially B/W, where some incompetent repairman put a brightener on the CRT to try to fix a dim image caused by droopy HV.

That was one of the last good sets Westinghouse built! All the following models were cheap corner-cutting, hot chassis, PC board jobs. Some of the lower-end 21" models, didn't even have a voltage doubler, a portable chassis in a 21" console. They were minimal performers.
On Decades TV, they were running some old Westinghouse Studio One. On one Westinghouse advert, Betty Furness was extolling the virtues of the Gated Beam Audio Tube, that always insured perfect sound.

Hoo Ha!:no: It was an elegant idea that lowered parts count and worked great until a bit of component drift set in.

At least some Westinghouse sets had the "quieting" or "buzz" control on the front of the set. If they were going to use the 6BN6, at the very least they should have made the quieting control a standard for the front apron. It needed frequent enough adjusting to justify it, that's for sure...

Ha. Didn't know that. L'arn something new every day.

Well, I did adjust it a bit and was able to get a little bit more brightness out of it -- didn't think to try that, thanks!

Vertical and horizontal lock are still very poor, and definitely degrades as the set heats up. Have been swapping out tubes, but none seem to make a significant difference. Even changed HZ output and damper just for grins and no change at all.

Brightness is getting better, but hold is bad. It loses vertical when changing channels on the DTV box and even when a show cuts between scenes it can lose vertical.

https://youtu.be/Pgm-8XGRZq0

I unfortunately don't have a HV or CRT tester or pattern generator. I'll check eBay and see if there's something available that won't break the bank.

I've been checking voltages and the third B+ (should be 130V) measures around 117 though the higher two (240 and 210) are dead on. I've changed the power resistors and all of the filter caps are brand new, so something is dragging it down. Also noticed that the AGC control on the back has absolutely no effect at all on the picture. I guess I'll start focusing there and see if maybe there's a bad resistor hiding out or something, since at this point all of the paper caps have been changed.

Big progress since day 1 though! Thanks so much for all of the suggestions!

FK

If both vert and horiz stability are bad, and the caps have been replaced, I'd look for a drifted or open resistor in the sync separator circuit.

I think I figured this one out actually. Turns out the tuning and fine tuning on the same shaft were frozen solid together and didn't even realize there were two. Was finally able to work it free and with the fine tuning dialed in the lock is solid both ways. Now of course, sound is best when tuned away from best picture, but that seems like more of an alignment issue -- problem for another day!

I was noticing the certain voltages were still low, such as the CRT screens and the boost voltage was about 520V where it should be 580. Checking the schematic again I realized there were two caps that I didn't mark as replaced which turned out were in the HV cage (duh). I carefully took it all apart, replaced the caps and carefully put it back together and.... no HV. Took it all the way apart again, triple checked the wiring and joints, carefully put it all back together and... still no HV. Verified DC resistance all the way across the flyback, resistance between the grid caps of horiz output and HV rect were both spot on schematic. Ultimately, it appears that in the jostling around, the filament of the HV rect decided to go open - no continuity between pins 2 and 7. Tried touching up the pins, removed the base and tested directly at the leads, but still open. Unfortunately this is the only tube I do not have a spare of, so at a small pause.

Before all of this I did experiment with the brightener and it did make a difference in terms of overall brightness however the contrast was still very washed out. As in, adjusting brightness/contrast it went from dim gray on gray to saturated white on white. Possible if the caps I did replace could have been causing this? (attaching snippet of schematic)

Thx all!

FK

Well, I've learned that apparently you can't test a 1B3 tube's filaments with an ohmmeter, and apparently my tube tester also cannot test a 1B3 tube so entirely possible that my diagnosis could have been inaccurate.

I went back and did a few more checks and found a few more out of tolerance resistors and one that was open and decided to give it another try. This time, HV did come up briefly but it started arcing after a few seconds. I took the HV cage apart again, even coated the leads of the new caps with corona dope, quadruple checked everything put it back and same thing.

https://youtu.be/mxDbkEfzzWA

The camera doesn't pick it up very well but the buzzing is accompanied by blue-ish flashes in the HV tube. From what I've read, blue means the tube is gassy, but everything was working fine before.

Ideas?

Thanks!

FK

Pull the cap off the top of the 1B3 and see if you can draw a nice blue arc to the tip of an ungrounded (plastic handle) screwdriver, if you get a good arc and the buzz is gone then the problem is probably after the tube, perhaps under the base of the 1B3. It could be a gassy 1B3 but those usually just glow purple without any noise.
It's possible you cracked it somehow and completely let the vacuum out, in that instance it might arc and buzz internally.

"Well, I've learned that apparently you can't test a 1B3 tube's filaments with an ohmmeter"

Huh? I just went out to the shop and measures about a dozen of them ... all were right around 2 ohms, pin 2 to 7.

jr

I read somewhere else that it requires the 15KHz AC from the flyback to actually light the thing... so that's not the case? Well, that lends itself well to the problem being the actual tube then. It must have just been barely holding on and taking it out and putting it back in just did it in. Have purchased two more so should have them by end of week. Edit: found a guy not too far from here selling a lot of tubes for possible use as an "art installation" that includes two 1B3GT's... hope they're good! Gonna go pick them up tonight.

FK

Pulled the cap, buzz is gone. No arc from the screwdriver... tiny little blue spark if you basically touch the cap but that's it.

https://youtu.be/Ms4351ADleA

What number, or, size is the picture tube? That arc sounds low, but, you never know.
Does your set have a width control, Horizontal Phase, Horizontal oscillator, or, width?
My guess is horizontal oscillator troubles. If not, something in horizontal output, of, Damper. Does your set use a hv capacitor on the hv rectifier?
Bill Cahill

Good news -- back in business, it was the 1B3 tube after all.

https://youtu.be/fsLuy2y1dy4

Brightness is still a problem, the above video is taken in a pitch black room with brightness and contrast up almost all the way before the image completely saturates. The brightener increases the overall amount of light produced, but the poor contrast is unchanged. This video is without the brightener. Would also say it looks brighter in the video than in person.

The picture is a bit noisy too, but that could be more related to the $20 DTV box that I'm using. Depending on how this all turns out, I might try to pick up a BT Agile for a better signal source.

The horiz and vertical lock are solid as long as the station is tuned in properly and both controls are pretty much at their extreme clockwise position. I've subbed out every tube at this point and tested every resistor, and all caps are replaced. The horizontal control is a little bit fritzy so I'm going to try to replace it and see what that does.

I purchased an VA62 pattern generator, a CR70 CRT tester and a 1000-1 HV test probe so should soon be able to determine CRT state.

FK

It's a 21ALP4 and has a 1956 date code sticker and Westinghouse branded with no evidence of repair so looks like the original. It doesn't use a HV cap -- attaching the HV portion of the schematic.

Also, does anyone know what is symbolized on the schematic by the x's and the dashed lines? I had thought that meant a disconnectable connector or the result a switch of some kind, but don't see either of these present.

The width control does have an effect on sync, and I have not yet tried adjusting the horizontal oscillator nor the horiz mult trim. The AGC control has absolutely no effect on the picture and I've checked everything I can find between the tuner and the 1st IF and all seems to check out okay. Perhaps it just doesn't have an obvious effect due to substandard signal from the $20 DTV box?

FK

The x's and dashed lines are SAMs notation for production changes. The solid line circuit is what was the original or predominant circuit. The dashed lines represents a circuit change. So you either have the circuit of the solid line or the dashed line (with the solid line circuit broken at the x's).

No switches or connectors are represented in this manner.

Got it - thanks. That had occurred to me, but none of those are listed in the Production Changes table they have. So for example, in later revisions, the second 330K resistor (R39 the blurry illegible one) was removed and both G2 and the focus control were fed off the same 330K resistor... those tightwads.

Based on that, I appear to have the earlier revision. Good to know!

FK

The AGC control should allow you to go from blank raster (no signal) to overloaded (negative picture with poor sync and buzz in sound) at full clockwise.

It may be an open control but what are the chances the set is producing a marginal picture and not one of those extremes?

That CR70 CRT tester should permit you to see the "cutoff" performance of the CRT, that is how well and linearly the control grid voltage G1 modulates the brightness, and by default, contrast.

Those coils between the 12BY7 and the CRT should be checked to see if one is open.

The voltages there vary based on the contrast (aka picture) control, and with it in the right position I can get the 210V on the plate of the 12BY7 and 160V on the CRT cathode, so the coils aren't open. I'll double check that the total DC resistance matches schematic.

I'm going to go over all of the AGC circuit again with a fine-tooth comb. I agree it doesn't sound right so it seems like it's the next thing to tackle.

FK

From the youtube video it looks like a low emission CRT to me. It has that silvery look on highlights. If the CRT tester you are getting has a rejuvenate function it might be worth a go. I've found that older B&W tubes rejuvenate quite well and usually last for a good amount of time. Colour tubes not so good.

Cheers.

I went through and checked all of the resistors in the AGC and video output circuits and found the 390K was measuring about 430K and the 15M was measuring closer to 30M. I replaced the 390K, and put back the 15M (since I don't have anything that high on hand), and in so doing it seems to have developed a new problem. There's now this pulsing effect in both the video and audio that isn't affected by tuning or any of the controls.

Still absolutely no effect from the AGC control on the picture. The schematic says the control is 750K, but it tests closer to 475K. However the wiper travel is smooth and resistance is correct all the way around and I'm not finding anything out of the ordinary at all.

Now for the good news. I tested the CRT on the CR70 and sure enough, no cutoff and tested at about 2 in the bad range. Irext, I took your advice and did a rejuvenation, and just like that I have cutoff and emissions in the 10-11 in the green. And now the picture is indeed brighter, though the life test drops like a stone. Is this effect typically permanent or have I just given it an adrenaline shot that will wear off?

This was how it tested after the rejuv, last night. I left it connected to the CR70 and tried it again this morning and while cold it started at about 2 in the bad and slowly creeped up to about 9-10 in the good range over about 3-4 minutes. Still had cutoff control, but not as good as in the video. Is there ever any benefit to hitting it again with rejuv/auto restore or is that just asking for trouble?

https://youtu.be/tGNYEsj6CGw

Not sure what's going on now with this pulsing/noise. Here's the new, brighter picture with that annoying new problem.

https://youtu.be/GSc_GAQxrsI

FK

That noise could be HV arcing. One of my sets did a milder version of that for a few weeks before the HV rect. died.

Was afraid of that. It was working fine two days ago but this just started last night before I did anything to the tube. I looked in the HV box and didn't see any visible arcing, and have tried two different 1B3's and no change. I'll try different horiz output tubes and see if that makes any difference.

I did notice that rotating the AGC control does have an audible effect on the normal HV sync pulsing/buzzing sound (whatever you call it), mostly from a volume perspective. So it's doing something, just absolutely no change on the picture. If the 15M resistor between B+ and the AGC control was bad or flakey (it tested at about 35M on my VTVM, and was beyond my DVM's measurement) could that cause the AGC issue and perhaps this new noise issue? The vertical seems to be affected most by this and occasionally the screen will go bright and saturated for a second. Just a thought...

FWIW tried injecting IF signal from the VA62 and still had same "arcing" and AGC problem. So at least we can rule out the tuner contributing to any of the problems... not like that was really a culprit, but oh well.

Thanks!

FK

That 15 meg resistor might be the cause of your problems, causing the noise and poor agc control.
15 meg sounds high, are you sure that is the correct part?
Have you cleaned the pins of the tubes in the IF amp?

jr

Yeah, 15 meg: brown, green, blue - see attached pic (yep that solder joint is factory) and schematic. How critical do you think that value is? If I put say two 2.2's in series would that be sufficient? It's not like there's going to be any useful amount of current through a 15M, it's just to complete the circuit but not actually really do anything right?

I've swapped around the IF tubes several times and wiggled them and doesn't affect the noise. I wiggled all of the tubes too and even tapping on the chassis does nothing so really doesn't seem like something loose. Going to hit an electronics store on the way home and if I have to stick six 2.2M's together I will, lol!

FK

Since the gold band indicates a 5 % tolerance, I would think that it is fairly critical. It is part of the voltage divider network that sets the AGC voltage. Likely 3-4.7 or 5.1meg resistors in series would be close enough (since the pot gives you some adjustment range).

jr

Too little of the schematic is shown to fully evaluate it's purpose, but it's value is likely critical. See that gold band on the end?...That signifies a 5% tolerance resistor. Most resistors in most TVs were 10%, or 20% tolerance. %5 resistors usually cost more and typically were not specified by engineering unless needed. You can make a series set of resistors if you need, but you probably want to check that it measures within 5% of the design value. If it is off a bit more it should not kill the set, but AGC may not set or react right...If you have signal and no more flicker that would confirm the resistor.


Speaking of resistors I've seen ones in series with the HV lead develop internal arcing...They may or may not test fine with 9V from your multi-meter, but at 10-30KV will arc and make RF noise that the set can tune and feed back to the picture and sound.

AGC stages especially non-keyed ones often had long time constant RC circuits with large value paper caps and or resistors.

Got it. The parts list doesn't call out a tolerance on that resistor specifically, but of course makes sense to replace with as close to correct value as possible. I'll see what I can come up with.

Attaching a larger version of the relevant schematic (really hard to get these legible and stay under the upload file size limit!)

FK

Good ol' Radio Shack!

http://www.videokarma.org/attachment...1&d=1503517290

Just 6 of these together and I've got myself one 15 meg 1/2 watt resistor... :rolleyes: