Any Zenith experts around Los Angeles?

[TinCanAlley]

Originally Posted by DaveWM

So the horz blanking pulses were in spec (amplitude)?
How good is the CRT? Maybe worn out and cut off no good.
does not make sence setup line not working, is the screen blanked out completely (cut off) or does the vert not collapse?

The CRT tested strong. The vert does collapse, but the screen drivers aren't enough to bring the line up. Now if I also increase the brightness and contrast, the line is visible, but then the screen controls are set too high when I switch out of setup. I've used the grid pattern of the generator with great success.

[DaveWM]

I would not bother with the jail bars until you get the setup sorted. With a strong CRT you should not have to max out the screen drives to get the setup line to work. I would look at CRT pin voltages.

[zeno]

On delta tubes typically one end of all G-2 controls at abt 250VDC.
The other end is also tied together at apx 900V "BOOST".
Check the 900V with a 1KV meter !!. Probably the G-2 are at
abt 400V. Normaly a strong jug will quickly give you the line.
Also look at all the CRT voltages to be sure they are OK.
It may turn out to be all the same cause.

73 Zeno
LFOD !

[Electronic M]

Originally Posted by zeno

On delta tubes typically one end of all G-2 controls at abt 250VDC.
The other end is also tied together at apx 900V "BOOST".
Check the 900V with a 1KV meter !!. Probably the G-2 are at
abt 400V. Normaly a strong jug will quickly give you the line.
Also look at all the CRT voltages to be sure they are OK.
It may turn out to be all the same cause.

73 Zeno
LFOD !

Good advice. I'd like to add that there are sneaky ways to do it with sub-1KV meters. On some tube era sets the lower supply rail is 300-350V. I've (when I've lacked a 1KV meter) measured that 350V with respect to ground, recorded it, then measured the 900V rail with respect to the 350V rail (only a 550V difference), then added the two numbers...It's crude but it works in a pinch.

[Findm-Keepm]

Originally Posted by Electronic M

Good advice. I'd like to add that there are sneaky ways to do it with sub-1KV meters. On some tube era sets the lower supply rail is 300-350V. I've (when I've lacked a 1KV meter) measured that 350V with respect to ground, recorded it, then measured the 900V rail with respect to the 350V rail (only a 550V difference), then added the two numbers...It's crude but it works in a pinch.

Brilliant! Never thought of that.

I just knew that we kept a VTVM for measuring boost. Blow a DMM once, and you'll never do it again. It was a selling point for Beckman meters back in the early 80s - you can measure Boost voltage directly, thanks to a 1500V DCV range.

Ground reference to B+ - another tool in the toolbox... Thanks.

[TinCanAlley]

All those things were tested a couple of years ago when I first got this set. It's all, pretty much, documented in previous threads. Tested the voltages at the socket, etc. All were in spec when tested back then.

There's ringing in a circuit and that's what I'm looking for with the jailbars. I'm pretty sure the problem with the setup circuit is a resistor. I have the replacements and will be working on replacing them.

Thanks