Magnavox CT 220 Anode Voltage.

[Xdevo1973]

Hi Everyone,

I finally decided to tackle this TV that sat in my basement for 10 years. It’s part of my Windsor Imperial top of the line console from 1948. I’ve restored a lot of radios and consoles but never a TV. I have it working pretty well. I’ve measured the anode voltage at 8kv. It drops in half with the brightness turned all the way up. Is this the right voltage? I’ve replaced the damper and the HV rectifier. I’ve replaced about 30% of the wax capacitors but not all of them, since I’m waiting for an order to arrive. I’m also waiting for a replacement horizontal output tube to show up. The CRT is a 12KP4.

[JohnCT]

Sounds a bit low, but it shouldn't drop that much with brightness change unless the tube is being over driven. If the HV drops by half from dark screen to normal picture brightness something is definitely not right.

If the picture "blooms" when you raise the brightness, that normally points to a bad HV rectifier tube or HV caps around the fly. If the picture shrinks when you raise the brightness, it's more likely a bad horiz out or damper.

John

[bandersen]

Typical anode voltage for a 12KP4 is 10kV.

http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/12KP4.pdf

[Xdevo1973]

Hi Everyone,

I think the anode voltage is ok at this point. It stabilizes at 8kv. I have another problem though, the 1N32 detector diode is intermittent. Is there a modern equivalent that I can order?

[mrjukebox160]

1N60 or NTE110A

[Xdevo1973]

Thanks for the information. I ordered some diodes. I also did something rather unorthodox and "fixed" the intermittent diode. I heated the negative end for about a minute with a soldering iron. I then tested it with a multimeter and it works consistently-even after I placed the diode in the freezer. I'm not sure how long that will hold up however, so I'll replace it with a new one once they arrive.