Admiral 20X11 restoration
 

I figure while I have my 20X12 up on the bench I might as well tackle this set too. It's the black set on the left.

http://farm7.static.flickr.com/6162/...e3ba82e0_z.jpg

It appears to be a very early revision of the 20X1 chassis. It also has quite a few original Admiral branded tubes including the CRT.

http://farm7.static.flickr.com/6072/...ae124f41_z.jpg http://farm7.static.flickr.com/6207/...b6f936d9_z.jpg http://farm7.static.flickr.com/6020/...36a690e2_z.jpg http://farm7.static.flickr.com/6153/...e95f14e6_z.jpg

When I pulled the knobs off, a few small washers came falling out. I was puzzled for a while - where did they come from ? Finally, it occurred to me that they are spacers between the inner and outer knobs. Without them, the knobs have a tendency to track when rotating one or the other. I have a few Admirals sets with these same knobs, but never found washers before. I suspect they all were lost over the years and never replaced.
http://farm7.static.flickr.com/6207/...98bc55cf_z.jpg http://farm7.static.flickr.com/6165/...3c4db996_z.jpg

It's had some work done over the years. I'd say about half the original caps have been replaced. The two multi-section electrolytics are original though.
http://farm7.static.flickr.com/6157/...26724d04_b.jpg

I decided to try something a little different with this project. Instead of shotgunning all the paper and electrolytic capacitors, I'm going to try to reform the electrolytics by powering the set up slowly over several hours. Then, assuming I get some signs of life, I'll troubleshoot the circuits that aren't working properly.

I'm also itching to give my recently restored Solar CB-1-60 a workout :)
http://farm7.static.flickr.com/6175/...f82d2c8a_z.jpg

I've got one of that model cap checker (someone mounted a new transformer outside the case on mine) that I've been meaning to test/restore. I wonder how it compares to the heathkit C-3?

Is there an EIA code anywhere on the CRT or other tubes, indicating who manufactured them for Admiral? Is that rust on the transformer laminations?

There are some key precision parts in the CB-1-60 like a big tapped resistor divider and 2% capacitors. I'll post details in the Test Equipment forum in a bit.

I'm not familiar with the C-3, but I do have a Simpson 383-A Capacometer I'll be restoring.


Here are the markings on some 6AU6s. The CRT base is marked National Video Corp. Chicago, 10BP4 while the bell is stamped "Admiral" and "S". Perhaps it's been rebuilt :scratch2:

Yes, it sure is rust. I've worked on three 20X1 chassis to date and they've all had rusty power transformers. I use a little Loctite Rust Neutralizer on them than some satin black enamel paint.

http://farm7.static.flickr.com/6128/...50de617d11.jpg

http://farm7.static.flickr.com/6176/...86a99293_b.jpg

The reforming seems to be going OK, but I had to use light bulbs of increasing wattage because my cheapo variac died a few months ago. It blows fuses instantly when it's turned on even with no load :(
http://farm7.static.flickr.com/6021/...0b499f34f5.jpg

I was just curious who sold them tubes. I suppose they may have even taken lowest bids. The 6AU6's are Sylvania (EIA 312).

[edit] 939 is likely 39th week of 1949

Rust converter is good on transformers.

Thanks for the info :thmbsp:
I'm just about up to full line voltage. One can is cool while the other is just a little warm.
While waiting, I did some troubleshooting on my variac and found the problem :)
Can anyone guess what it was ?

I have had no experience with Chinese made imitation Variacs, but based on experience with the Japanese imitation species that flooded US in the late 1940's and early 1950's, causes for shorted imitation Variacs in order of probability:


1) Line bypass or wiper bypass capacitor failed

2) Insulating washer on the spring loaded wiper failed

3) Incorrect wiper adjustment allowed the wiper to over extend and an arc melted a bit of solder, which shorted adjacent turns on the winding

4) Carbon wiper brush fell out and the metal holder shorted near turns on the winding


Or, finally, if the fuse blowing is not instantaneous, but takes a couple of seconds, the fuse holder spring.

James

The power cord doesn't look like it was strain releaved very well. Might have gotten pulled real hard and the connections crossed.

I have the same variac, it blows fuses when trying to power the 525 watt 21-CT-55. lol Other than that, it works well.

None of the above. The culprit was the cheap AC meter right across the output socket with no protection. The meter coil shorted out.
I clipped it out of the circuit and the variac is working again :)

Well, I was able to get a one inch high raster on the original caps. No sound or video though. First, I tested all nine electrolytics - seven are in two multi-section cans. Only the replacement cap in the center of the chassis tested good. Two others had minor leakage. The others were all open.

So I tacked in replacements for the open ones, but now I had no sound or raster! Cleaning the tarnished tuner contacts got me some good sound. but still no HV.

I then got a scope on the hor. oscillator and found it was way off frequency so I rebuilt the whole circuit and the HO circuit too.

Every single paper cap I tested was either very leaky or way off value. Only a few of the more modern replacement caps were good.

Still no HV :(

Then, while fiddling around with the focus control, I suddenly got a raster back :scratch2:

I got an ohmmeter on it and found it was open :( Rotating it fully counter clockwise would bridge the bad section and get power going through to some circuits.

I tacked in a temporary replacement and finally got a picture and sound :banana:
http://farm7.static.flickr.com/6158/...c739f141_z.jpg

http://farm7.static.flickr.com/6128/...9bc3ca0b_z.jpg

The vertical height control is maxed out and the picture is still squished so I'll tackle that circuit next.
http://farm7.static.flickr.com/6162/...711f6f6c_z.jpg

So...You ended up recapping it. I knew you would.

60 year old caps are hopeless in my book. Why chance it?

I like that set, BTW. I'd like to find a good one to restore for my collection.

Keep at it, Bob.

Thanks. I knew I'd recap it too, just curious. I also recorded some video I'll be posting to illustrate how futile it is to try running vintage sets on the old paper caps.
As for the electrolytics, while I'm sure it is possible to reform them in some cases, I've never had any luck and don't really see the point.
Why not just replace them too while the chassis is out on the bench and not have to worry about them ?

After rebuilding the vertical circuit, I have plenty of height :)
http://farm7.static.flickr.com/6026/...f1a2c718_z.jpg

Next up, remounting the restuffed cans.
I also found a number of resistors that were off 100% or more in the video IF which I replaced. So I'll go through an alignment when it's all back together.
http://farm7.static.flickr.com/6169/...af8e3f8b_z.jpg

Speaking of Solar cap analyzers, guess what I ran across when straightening up my shop last week?

http://antiqueradio.org/art/temp/Sol...Unrestored.jpg

Let me know if you think it works well enough to be worth restoring. I doubt I would use it a bunch -- my attitude toward 60-year old electrolytics is that they all deserve to die the true death -- but anything with an eye tube warms my heart and I hate to have non-working things piled all over the place.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Absolutely! I mostly use it to test mica caps. It's nice to know if the originals are really bad before trying to try down replacements with oddball values.

I think this is the first time I ever bothered to test electrolytics. It was interesting to see how much better new caps test compared to vintage ones.

Micas, OK -- I will give it a whirl. Just found a decent 20-page manual online, too.

Nice job on the TV, by the way. My first Admiral is still languishing in the back row, but I'll get to it some time before next summer.

Phil Nelson

If memory serves, the main issue with the old EL caps is the electrolyte tends to dry out. Most had a paste of water and borax(?), and the water would slowly escape or be driven out by heat as the caps got warm. Initially, of course that would be from the tubes, but as they lose efficiency, the caps start producing their own heat as well...

There was a note a while back here where someone said that oil-filled caps were rarely bad; with water-based caps, since the innards are rarely damaged, you _should_ (in theory) be able to re-hydrate them and have them work again.

Could you please link that manual. I'd love to read some info on it to get me fired up enough to fix mine.

Tom C.

I've created a new Solar CB-1-60 thread in the test equipment forum.

You'll find a link to the manual and parts list there.

Thanks! Spotted that thread first, and read all but the linked pages (I'll read those soon).

I received some salvaged controls courtesy of grimer today. They came well packed in electrolytic peanuts :)

Unfortunately, this focus control is bad too. Not totally bad though. I get the correct 0 to 1,500 ohms on one leg through the full rotation. The other leg is open so there's probably a break very near that lug.
http://farm7.static.flickr.com/6215/...14dcafbce5.jpg


The original focus control in my 20X12 had failed too! I'm starting to suspect a design flaw :scratch2:

Time to investigate. I carefully popped open the one that originally came with this set by prying back metal tabs. Sure enough - there's a definitely break about 20 turns from one end.

This resistive (nichrome wire?) is a pain to solder so I wedged in a scrap of copper foil plated with gold. It seems to work OK, but there's a noticeable "bump" when the wiper goes over the damaged area. Luckily, this control isn't adjusted much and the damage is near one end.
http://farm7.static.flickr.com/6173/...21ae88af94.jpg

I'll pop open the one from grimer too and try to repair it. Whichever works better will end up in the set.

Yep, the control from grimer had a break is almost exactly the same spot! Once again, a gold plated copper shim did the trick :)
http://farm7.static.flickr.com/6174/...3691d4ffec.jpg http://farm7.static.flickr.com/6051/...1e57ba1a76.jpg

That's a pretty ingenious solution to that problem. I'll have to remember that trick. I suppose one would also be able to limit the travel of the wiper by putting a block of some plastic superglued to the inside of the control.

According to Sams, the focus control in later production units was 4w/1350 ohm. Early was 2w/1500 ohm.
So, you might want to put in a 4 watt pot. I have had the 4 watt burn out
also. I have found 4w/1500 ohm ww focus controls from other sets of the same
brand as used in the Admiral, and been able to remake a good control.
Your solution looks good.

I do have just one spare of those 4W variety. It's noticeably beefier and I'm going to use it in my 20X12. I'll use one of these 2 watters in this set and hope it holds up.

youtube vids?

I finished a total recap and replace many out of spec resistors.
I added a 220 ohm resistor to one leg of the focus pot to compensate for the shorted windings in the damaged area.

http://farm7.static.flickr.com/6047/...c4a348e2_b.jpg

The linearity is pretty good.
The horizontal is off a little (squares on the left are wider than on the right), but the linearity adjustment coil doesn't have much of an effect.
http://farm7.static.flickr.com/6233/...fc4dec60_z.jpg

Here's a multi-burst bandwidth test at 0.5, 1.5, 2.0, 2.5, 3.58 and 4.2 MHz.
Curious that the middle bars (2.0 MHz) are less distinct. I suspect the IF has a pronounced double hump response.

http://farm7.static.flickr.com/6039/...a17468de_z.jpg


part 1
part 2

Still working on part 3. It will cover alignment.

I finished with the alignment. Here's the video IF response before and after.
It really wasn't that bad to begin width. The service info calls for the peaks to be within 30% of each other. I tweaked the coils to equalize the height, but the only way to get a flattop is to kill the bandwidth.

My scope is set for 1 MHz / div so the bandwidth at 50% is about 3.2 MHz just as the service info calls for.

I suspect the IS was a design compromise to fit the chassis into a relatively small cabinet. The Admiral 20A1/20B1 stagger tuned chassis I've restored previously perform better. Then again those sets use a split chassis with plenty of room for more complex circuits.

http://farm7.static.flickr.com/6211/...dbea39e9_z.jpg http://farm7.static.flickr.com/6046/...589efc58_z.jpg

The picture is prrety good except for some faint diagonal interference lines.
http://farm7.static.flickr.com/6230/...0ac63eca_z.jpg http://farm7.static.flickr.com/6233/...cc2e04a8_z.jpg

Bob - You have a nice clean chassis a couple of pictures back. How did you get it that way?

I got lucky this time - no rust! I just used a damp rag to clean the the top of the chassis, yoke, tubes etc. The underside was already nice and clean.

I've been getting little shocks when my hand brushes against the CRT. I figured it was just static build up since the air is dry.
When I removed the CRT to replace the rock hard mounts, I discovered the CRT grounding wire was missing!
Here's one from another set. It's a short, curved piece of strong wire that hooks into the chassis and makes firm contact with the aquadag CRT coating.

I fabricated a replacement and no more shocks :)

With the CRT out I was able to scrape of the old mounts and clean up the chassis. Then I cut some new mounts from a sheet of neoprene and glued them down with GC rubber-to-metal glue.
http://farm7.static.flickr.com/6115/...506af757_z.jpg http://farm7.static.flickr.com/6111/...1da7415f_z.jpg


I also popped out the tuner for some cleaning and replaced a few out of spec resistors. It's pretty cramped in there!
http://farm7.static.flickr.com/6019/...a59fc65a_z.jpg http://farm7.static.flickr.com/6096/...31fd9b4b_z.jpg

Then, I finished up the alignment. Here's the equipment I used.
http://farm7.static.flickr.com/6103/...1b873764_z.jpg

Here are some post alignment screen shots.
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I'm calling the electronics of this set done. Now on to cleaning up the cabinet.

Nice sharp picture. Another one for the showroom.

That Tuner looks exactly like the one in my 1949 era Emerson 639. Wonder if these tuners are the same and if they were simply common parts used by lots of manufacturers. I took my tuner apart and then lost one of the two wires that holds it together. I fabricated a wire. Later I found the one I lost and plan to some day replace it back.

Carl

Lookin' good, Bob.

I'm pretty sure that's a Standard Coil turret tuner. I think Standard Coil was the name of an independent tuner manufacture.

Thanks guys :)

No matter how careful I am, I keep losing bits and pieces too. I rarely find them later though :(

Here's a photo of my 639. It sure looks like the same tuner :yes:
http://farm7.static.flickr.com/6008/...4d2e8435_z.jpg

Bingo! I was flipping through a copy of "Television Receiver Servicing" by Milton S. Kiver and found a couple pages describing this tuner in detail.
http://farm7.static.flickr.com/6047/...9276d72d_z.jpg http://farm7.static.flickr.com/6117/...3d9cc3f8_z.jpg

What is this?

http://antiqueradio.org/art/temp/Gizmo.jpg

Phil Nelson

P.S. Nice picture.

It's a Wavetek 1002 sweep generator (specs). It works great and was my main generator until I picked up a much newer Wavetek 1080 with the nifty VFD readouts.

Those big knobs remind me of some parts of the human anatomy. I wonder what was on the cabinet designers mind at the time that was thought up?......:scratch2:

:D The larger knobs do make it easier to dial in a frequency.

Here's all the stuff pictured.

Wavetek 1080 sweep generator
Wavetek 1002 sweep generator

HP 54600B oscope

Heathkit IG-102 RF gen.
Leader 17A RF gen.

Kikusui 1120 frequency couter

RCA VoltOhmyst VTVM (off camera)