Admiral 20X12 restoration
 

I picked this set up on ebay a few years ago. It's one of the few times I went for a set that had already been restored. Also the seller warned me that it had stopped working recently. These don't show up often so I took a chance.

After it arrived, I quickly discovered that the HV anode cap had fallen off the CRT. I replaced it and the set worked :D
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At least for a while anyway. After a few months of occasional playing it produced a high pitched squeal and the picture disappeared :(

Grimer says he has a 20X1 part chassis so I figured I'd better haul it up on the bench and have a look.

Note that the combo power/volume/focus control has been replaced with just the power/volume. The focus control is now located in the lower right.
Otherwise, whoever worked on it did a pretty good job.
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I started out by poking around in the HV cage and found the 1X2 had a short. I replaced that but still no go. I then check the hor. oscillator, width and linearity coils plus the flyback. All were good. Finally, I found the 1X2 tube had a short. I replaced that and got a raster back :)

Unfortunately, it's very dim :( I tried adjusting the ion trap and hor. drive, but something just didn't feel right. Usually when you power up these old sets you can kinda feel the power emanating from the HV cage - maybe even hear a little 15 kHz ringing. I wasn't getting that so I pulled out an HV probe and only measured 5kV instead of 9kV. Back to more checking...

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I gotta get a bakelite tv. That's on my keep my eyes peeled for list. I like the way they look.

They always remind me of a yummy chocolate bar. :D Love that ribbed cabinet.

How the heck can a 1X2 or any HV rectifier have a short? All you have in there is a filament and a plate thats a mile apart. I guess maybe if the filament opens and flips out?

You got it :yes: I did my best, but it's tough to photograph tube innards. The one on the left is good, the shorted one is on the right.

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HV tube shorts happen when there is a momentary external short of some type: flashover from the anode cap to aquadug, anode wire to chassis.., that draws an arc in the HV rectifier which pulls the material off the cathode. When I see a blown HV recitifer I always look for corona or leakage which can cause flashover.

Oh, I note the anode cap had fallen off prior to getting the set, it probably had already shorted to the chassic, starting the cathode damage.

Yesterday I was working on a Curtis Mathes set which had HV but no picture. It turned out the 2AV2 focus rectifier was cracked. Replaced it and the picture came on but the focus was bad.
I checked the focus voltage and it was only about 1 kv. I then sprayed the tube pins with Deoxit and pushed the tube in and out several times in the socket. Then I got around 3kv and the focus was good.
I think the problem was a high-resistance connection at the socket, maybe causing too much voltage drop in the filament circuit. Maybe you are having a similar problem.

Also I would check the horiz output tube voltages, have had low screen voltage caused by a bad resistor cause poor HV.

I swapped out the 6SN7 hor. oscillator and tried another 6BG6. That helped. I also replaced the 47 ohm 6BG6 grid resistor which had drifted up to about 58. That helped too.

Then I tested the CRT. Emissions are OK, but the life test is weak and I had no cutoff control with bias at -52v. If I dropped it to -36v, I got some response when rotating the cutoff control but still not right. So I used the rejuv. and auto-restore functions as indicated. That helped, but the cutoff is still weak.

I'd try swapping out the CRT, but someone did a sloppy base repair and I can't slide it through the yoke, etc. without filing it down :(
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At any rate, here's where I'm at. The picture is brighter and the bandwidth looks good. However, I have some horizontal tearing. I guess I'll do some more checking of the sync and horizontal circuits.


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If they used straight up epoxy for that repair, it should peel off the outside of the neck without too much force - it doesn't stick well to smooth surfaces like glass or plastic, unless you rough them up a bit first.

YIKES No!:yikes:If that epoxy is engulfing any of the wires where they emerge from the glass (which looks to be the case), any movement of the epoxy will likely break them off. Grind the epoxy down flush gently.

If the base is fitted properly to the glass, there will only be a very thin seam where they meet- and that will break or can be cut very easily without disturbing the epoxy under the cap.

Yeah if the base were intact that would be true. But there looks to be a BIG chunk broken out and missing, and the resultant gap rather sloppily filled in with epoxy. 'Least that's the way it appears to my enfeebled eyeballs. :pity::(

off to the left!
 

I noticed that your Admiral in one of the pictures has the picture off center. Mine is like that too. My focus/centering coil is all the way and, it will fill the screen but still is off to the left. Are you able to get decent centering or is this a trait of these TV's?

right behind with a 12X1
 

What a nice clean chasis and what luck my 12X1 looks the same.

Yes, indeed there is a big chunk of base missing and the epoxy was slopped in. I did some more work on the set and have a better picture. So, for now I'll just leave the old CRT in there.

Yes, I have a pretty good centering range with the lever. The horizontal centering is also effected by the hor. drive, hor. lock and hor. sync.

I found a few out of spec resistors in the hor. oscillator circuit and just replaced them all. That threw the oscillator off a bit so I went through the adjustment instructions in the service manual. When I finished with all that, here's what I got. The horizontal linearity isn't perfect, but overall not too bad I think.

First picture is from my Leader LCG-400, then a local low power OTA VHF transmission. Last two are from a converter box.
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Not so clean topside :( This set came from Florida and I suspect the humid air contributed to this rust. I'm going to tackle it with some naval jelly then paint the worst areas to keep it at bay.
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After some chipping with a knife, a whole lot of filing and a little vaseline, I finally got it out :)

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Now I can really get in there and clean the chassis. I'm also going to try a different CRT that has a better cutoff.
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I'm slowly winning the rust battle. I'm doing a section at a time. Once the rust is dissolved, I'm left with deeply pitted steel. I've been painting that with Rustoleum "rusty metal primer" then aluminum paint. I think it's a little cheesy looking, but should keep the rust at bay.

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I find it lurking everywhere!
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While waiting for the rust to dissolve, I've been checking everything else including the tubes. Most were good, a few marginal and this nearly dead 6J6.

Shorts, leakage and nearly no emission.
I find it amazing that this set is functional with this RF oscillator/mixer tube installed in the tuner.

Of course it works even better with a good tube ;)
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Is amazing how some sets can function with half dead or nearly dead tubes! Like that Telerad oddball set that I'm still working on, virtually all of the 6SA7's had little or no emisson but the TV still seemed to work! Weird huh? :yes:
BTW I was rather impressed at those upclose shots of that CRT, such a sharp image and good definition too, not bad for a weak picture tube, I can only imagine what a good CRT will perform like...

Cheers Glen

Nice work on that chassis! I don't envy the corrosion battle, My chassis only needed the dust cleaned off.

I just noticed you posted in my 20X11 thread that you have a couple now. That was quick :D

Actually I have one and a cabinet that is floating right now. I am getting a HV cage from grimer so I can jump back on it. I will be looking at some leftover chassis from a tv shop that closed in the 60s either this or next weekend, that should be fun. Maybe I'll find the guts for it. BTW your videos are a big help. There is no way I'd ever get these running without the internet.:thmbsp: