Need help.

[Bill Cahill]

Admiral 20X122 console tv.
I went entirely through this set. It played great on bench. Put it in cabinet. Still played great. Two days later turned it on, and, loud buzz in the sound, and,a negative picture.
Still haven't found the problem. I even replaced all the mica caps.
Also, would like to pick up a good orinimal speaker for Set, and, bottom chassis tray.
Thanks, Guys.
Bill Cahill

[Electronic M]

How is the AGC control behaving?

[bandersen]

The 20X1 chassis doesn't have an AGC control. Here's a link to the schematic: http://www.earlytelevision.org/pdf/A...Sams_100-1.pdf

I'd start by checking the voltage on the 6AS5 audio output cathode.
This set uses a stacked power supply design with the class A audio output tube doing double duty as a voltage divider for the lower B+ supply rail.

[Bill Cahill]

This is a tv only. Bakelite console cabinet. You are right, though. No AGC control, except the usual contrast control doubling as agc control.
I don't believe it to be a stacked power supply, though I could be wrong.

[bandersen]

Yes, it uses a stacked supply. You should have about 140 volts on the cathode (pin 1) of the 6AS5.
The contrast control which varies the gain of the video amp is tied to that point.

[Bill Cahill]

OOps. You're right. Thanks for the reminder. Maybe that filter there went bad. Thanks for helping me.
Bill Cahill

[Bill Cahill]

Originally Posted by Electronic M

How is the AGC control behaving?

As he said, there is no AGC control. The contrast control doubles for AGC.
No, to my answer. The images fade out with some of the hum.
Bill Cahill

[Bill Cahill]

I'm wrong on model number. It's our favorite bakelilte ten inch console. 20X122
I also need some other parts, such as a good original speaker with original cable, and, plug, under the chassis metal shield, a plastic screen in better shape, this one is badly scratch.
Thanks.
Bill Cahill

[Bill Cahill]

Can anyone help me??
At one time I had it playing well. Now, I get a loud buzz in the speaker, and, a negative picture.

[Bill Cahill]

Stupid me. I forgot it's our favorite 10" bakelite console.
Thanks.

[bandersen]

Have you checked the 6AS5 cathode voltage as I suggested earlier ? Or just try swapping out that tube if you have a spare.

[Bill Cahill]

No, not yet. But, I don't have that tube in stock.

Thanks, though. Can anyone spare that tube??
Thanks.
Bill Cahill

[Tony V]

There are several of those tubes on Ebay. They are NOS and between $2 and $4 with free shipping. Cant get no better than that.

[Bill Cahill]

Thanks, Tony. Bill Cahill