Admiral 20B1 Combo restoration

[SwizzyMan]

Well I finally found another project to keep me busy... I picked up a Beautiful Admiral 20B1 combo radio,phonograph,and television! Found this awesome set hidden behind some furniture and phonographs in an antique store in Daytona Beach where I was spending my Labor Day weekend. I am a frequent visitor to this antique store whenever I go over to Daytona (which I frequently do) and was surprised I found this set hidden in a corner. I was also sort of mad at myself for walking by this set multiple times and not noticing it. With a price tag of $125 I decided it was worth the risk. The owner of the store said she had turned the set on and it started smoking. That almost scared me away, but once I saw that everything was there and the cabinet was in decent shape I decided why not. Brought it back to the house and did an inspection. Very dusty! I found 5 or 6 tubes tested borderline weak and some tested almost dead. The picture tube is very weak with the needle barely making it out of the bad zone and into the beginning of the question mark area. Might have to pick up a new 12LP4 or 12KP4 if anyone has one. I plan to do a full recap of the paper and electrolytics in the television and power supply chassis. I will try to preserve the looks of the original wax and electrolytics by restuffing them as I go. I noticed that the 3k sand resistor connecting to the focus control pot was losing its sand coating and the resistance wire was broken in places. That resistor tested completely open. Also the 40/40 main filter cap on the power supply chassis has bulged and spilled its guts everywhere. Yuck! I sure do hope no real damage was done to my power transformer or anything for that matter. I have no idea what the condition of the radio or the phonograph is. Will tackle that after the TV portion is restored. Hopefully this set will be an easier one to restore than the CTC-7! Also please know I did NOT turn this set on!

[old_coot88]

Old B&W jugs can often test 'waay down in the red and still show a decent pic.

[Phil Nelson]

I am just finishing a nearly identical Admiral (chassis 20A1) at the moment.

That should be a much easier project than the CTC-7. Those chassis are laid out with plenty of elbow room, easy to work on. Admirals are well designed and they perform very nicely. Nearly everyone has success with them. These models are popular and well known to collectors, so if you hit a snag, advice should be available.

This article has restoration notes on my 24C15 console using the 20B1 chassis:

http://antiqueradio.org/Admiral24C15Television.htm

The only unexpected wrinkle was needing to replace the little mica caps inside the audio IF cans. This problem is not universal, but if you eliminate more obvious causes and can't get normal volume after doing the audio alignment, those two little micas are worth checking out.

In that case I removed the transformers completely, but in my current project I removed only the cans and left the transformers mounted in place. No need to disconnect and reconnect all of the xfmr wires. An even easier approach would be to cut the old micas in half from above using a wire cutter, leave them in place, and wire the new ones to the pins below the chassis; that eliminates the need to disturb the hair-thin wires on the transformer. Always more than one way to skin the cat

Regards,

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

[SwizzyMan]

Well this set is definitely a high hour set. I tested 16 tubes in the TV portion of the set. 11 of them are bad.... 2 6SN7's and 7 6AU6's a 6GB6G and the 1B3GT are bad.... That isn't good!

[SwizzyMan]

Replaced all the paper caps in the TV section and the bad filter cap on the power supply section. Did a power up test. No sound but very weak high voltage (2KV) most likely cause is the weak 1B3 rectifier. Obviously didnt get a pic with such low HV. Do any of you have a sams for this set you could copy for me?

[Kamakiri]

http://www.earlytelevision.org/tv_sc...s_admiral.html

[SwizzyMan]

Thanks a bunch!

[SwizzyMan]

Replaced the 1b3. Still no raster and low HV. I also can smell a little smoke coming from the chassis. I don't see any smoke or see any burnt components. Remember I did recap the main TV chassis and the power supply chassis. No sound either... Anyone know what may be going on?

[Phil Nelson]

I'd start with some basic voltage checks. The Riders manual at http://www.earlytelevision.org/tv_sc...s_admiral.html has two pages of charts showing what voltage you should be getting at every pin of every tube.

Phil Nelson

[SwizzyMan]

I'd suspect some of the big 2 watt resistors in the TV chassis could be off value. I know that those can drag down my HV if they are bad. Will check them and pick up new ones as needed.

[SwizzyMan]

Just encountered something really interesting with the 12LP4. This tube is a rebuilt tube rebuilt by national video corp in Chicago. When I powered the set on in complete darkness I got a extremely dim picture for a second then it disappeared. After taking a closer look at the face of the CRT I could barely see some damage on the phosphor in the center of the CRT face. looks like a bit of the phosphor was sucked off when the tube was relieved of its vacuum when it was rebuilt? Not noticeable in normal light just when I can see the filament from the CRT glowing inside the neck when looking through the screen. Did rebuilders usually cut the neck off with the vacuum still present inside of the tube? I have no other possible explanations for this.

[SwizzyMan]

OK replaced the big 2 watt resistors and one off value 1 meg resistor on the 1b3 socket. Brought up my hv about 6 or 5 KV with the ultor measuring 7.8KV way too low... What else could be causing this problem? Still no picture. Ultor voltage should be 16 or 12 KV I think.

[bandersen]

Around 9kv is typical for a 12LP4 so you're not too far off. 7.8 should be enough to produce a decent picture.

[SwizzyMan]

I read it a bit wrong... I am at about 6.3KV is that too low to produce a picture? Know that this crt is weak.

[bandersen]

That's normally enough to produce a picture. Do you have nothing on the screen ? Have you tried moving the ion trap magnet all around ?