1982 Zenith 25" System 3 with Space Phone

[Alex KL-1]

Originally Posted by radiotvnut

I picked up this 1982 25" Zenith System 3 console with Space Phone and the deluxe audio amplifier for free from an estate sale.

I can tell that the 9-160 board has been serviced (good luck finding one that hasn't, LOL). At first, I thought it was a case of simply not having CRT heater voltage, since I heard HV come up and I had sound (noise from the speaker, no signal connected yet) and evidence of channel change. However, after listening closely, it sounds like the HV is ramping up at turn on and immediately shutting down, which is confusing because I thought everything was powered from the flyback and it seems like if the horizontal sweep circuit was shutting down, then that would kill everything.

Later, I'll connect a signal to the set and see if I can at least get audio from the DTV box, and I'll put an HV meter on the 2nd anode, to see if the HV is ramping up and then going down.

Alternatively, you can probe the video output +B (for output transistors for driving the CRT cathodes). Generally is anything from 175 to 200V in most TV's from this era. Too large value can trigger the HV protection (if TV have one).