Electronics > Repair

Fix vertical hold on a monochrome monitor

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rea5245:
Hi,

I have a monochrome monitor with a beautiful amber display, but I can't get the vertical hold to stay put.

It's a Magnavox 7BM623 074T. I can carefully find a sweet spot for the V Hold to stop the screen from rolling, but if I turn the computer and monitor off then on, it loses the hold and starts rolling slowly.

I've replaced all the electrolytic caps and the V Hold potentiometer. The problem remains.

Anything else I can try?

Thank you,
   Bob

bob91343:
You would get better results if you had a schematic.  The synchronizing pulse for the vertical oscillator is apparently weak or nonexistent.  You need to find that circuit and troubleshoot it.

PKTKS:

--- Quote from: bob91343 on June 11, 2021, 05:48:00 am ---You would get better results if you had a schematic.  The synchronizing pulse for the vertical oscillator is apparently weak or nonexistent.  You need to find that circuit and troubleshoot it.

--- End quote ---

That is true..

When you *CAN*  pause the rolling even for a second...

it  means the local oscillator is perfect

but you have problem w/the sync integrator..
Just try to find hard that part of the circuit...

The fault should be at the integrator.

Paul

rea5245:

--- Quote from: bob91343 on June 11, 2021, 05:48:00 am ---You would get better results if you had a schematic.

--- End quote ---

Yeah. Alas, I do not, and Google can't find one either.

themadhippy:
I thought the correct fix for a rolling crt display was a sharp thump on case,or does that only apply to televisions?

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