Admiral 20B1 Combo restoration - Page 3 - Videokarma.org TV - Video

SwizzyMan · #1 10-10-2015, 01:15 PM

My bad the power supply is the problem. I cant run the power supply chassis without the tv chassis hooked up since the tv supplies the filaments and other voltages besides the AC to the power supply..

SwizzyMan · #2 10-10-2015, 04:42 PM

Also not sure why I can't get a raster.... I have an ultor of about 7.8kv

***Eric H*** · #3 10-10-2015, 06:08 PM

Everything on this diagram is on the power supply chassis isn't it?

With the power supply disconnected from everything else you should be able to put 120VAC on the primary where the Phono Motor is attached and run the power supply by itself.

If you still get red plating on the rectifier then the short is on the PS chassis, if not then it's further downstream in the TV or radio chassis, it should be fairly easy from there to figure out exactly which circuit has the short on it.

I'm guessing your High Voltage is low because of the drag on the power supply voltage.

El Predicta · #4 10-10-2015, 06:22 PM

I may have an extra power supply, will check.

SwizzyMan · #5 10-10-2015, 06:41 PM

Eric, You may have missed this but I did solve my red plating issue (broken ground lead on the electrolytic) My problem now is that my filter choke I THINK is smoking. And I can't seem to find out why.

SwizzyMan · #6 10-10-2015, 07:43 PM

Also I forgot to mention. I forgot to replace a .002 uf paper cap on the output plate bypass. That could be a potential problem!

SwizzyMan · #7 10-11-2015, 02:33 PM

With the power supply disconnected from the TV and the radio but turned on everything seems to be fine now. No smoke, nothing..

SwizzyMan · #8 10-21-2015, 04:46 PM

Anyone have a spare 20b1 combo power supply I could have?

Electronic M · #9 10-21-2015, 04:53 PM

If the supply don't smoke running disconnected from the TV and radio chassis, and is producing rated or higher voltage at all outputs, then the power supply chassis is fine. There is likely a short or excessive power consumption in the TV and or radio chassis.

SwizzyMan · #10 10-21-2015, 04:55 PM

Will check for anything this weekend. Didnt think I'd have so much trouble working on this.

SwizzyMan · #11 10-28-2015, 05:44 PM

This set is really confusing me. The power supply is no longer smoking but I STILL can't get a raster on the CRT i have about 6 to 7 KV but the CRT is weak. But I can't even get a very dim raster. This is really puzzling and I am not sure where to start with diagnosing and fixing this problem. All filter caps stay cool (I will replace them when I can get a raster). All tubes have been replaced except for the horiz out tube that is somewhat weak and is only a quarter way through the good zone and fails the trans-conductance on my hickok 600a. Any ideas where to start?

bandersen · #12 10-28-2015, 06:17 PM

That's definitely enough HV to produce a raster. Try moving the ion trap magnet around. If it's the typically dual blue/black Admiral magnet, the black magnet goes towards the base of the CRT.

Also, check the voltages on G1, G2 and the cathode of the CRT. Could also be an issue with the focus coil. Check it's resistance.

Phil Nelson · #13 10-28-2015, 11:07 PM

You can rotate the ion trap magnet as well as push it forward or back along the neck.

There should be a definite sweet spot where the CRT achieves maximum brightness with no shadows around the screen edges.

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

holmesuser01 · #14 10-29-2015, 04:20 PM

I'm restoring a DuMont RA-113. It was totally dead when I got it. Someone had burned up the power transformer when they plugged it in. I have replaced most of the electrolytics, and some of the other caps. So far, I've now got sound, and FM radio! I've also got no image on the screen. My CRT checks fine, and I now have 12kv at the anode after replacing the HV capacitors. I can hear the vertical running. I'm not seeing any signal from the video output tube, yet. It's a challenge that I like. I'll get it going, yet!!

SwizzyMan · #15 10-29-2015, 06:20 PM

Good news!! Got a raster and picture finally! Was an adjustment of the ion trap. The picture is lacking vertical height,lack of focus,and the vertical and horizontal holds are pretty bad and barely lock at all and dont lock for long. I also noticed that a small little portion of the h out tube plate is glowing red. It is concentrated in the middle of the plate on two sides and is a small dot. Picture is nice and bright. I did a full recap of all the paper caps in the TV and some off value resistors. I have not replaced the filter caps on the TV but none of the caps are getting warm but one does get a bit hotter than room temp which is part of the vertical sweep. Any suggestions on where to go from here? I would assume restuffing the filter caps would be a good idea.