G0-7 partial vertical collapse

yaryar

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Was hoping this one would have been an easy fix as the vertical circuit is pretty straightforward, but no luck. This chassis was recapped and new flyback installed, as well as Bob Roberts pot kit. Monitor has been working just fine in my Millipede for the last year, until the other night. Walked up to the game and found that the left half of the screen was completely gone, and the right half is about 25% collapsed. So far, this is what I have done:

1) Swapped all 400 series caps, IC 501, and vertical transistors from a known working chassis.
2) Replaced FR401
3) Did some continuity checks on the chassis

Anything else I could have missed before I pull the monitor and set it up on the bench and put the scope on it??
 
Did you replace C402 the 2.2Uf 16 volt tantalum? I had one that was in complete vertical collapse. Turned out it was shorted.

I would try replacing it. I have several and they are like a dime for a dozen. So if you need one let me know and I'll put one in the mail.

Ed
 
Did you replace C402 the 2.2Uf 16 volt tantalum? I had one that was in complete vertical collapse. Turned out it was shorted.

I would try replacing it. I have several and they are like a dime for a dozen. So if you need one let me know and I'll put one in the mail.

Ed

I'll check that cap out shortly. Also, I forgot to mention that I did swap D401 also and no change. I'm leaning towards a cap, because when I swapped several of the above mentioned parts, the screen did come up for a few minutes, then went to the partial collapse. Now, even if the chassis sits for a few days, when powered up it goes straight to the partial collapse. Tapping on the chassis doesn't cause any changes so it doesn't look like a cold solder joint. Continuity checks are good for the vertical section of the chassis also.
 
Subscribing. I have the exact same problem only total collapse. New fly. New caps. Ugh. New deflectors coming in tomorrow.

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Your horizontal output transistor is fine. Otherwise you'd have no high voltage and no image at all.

A broken vertical hold or vertical height trimpot can cause vertical collapse.
 
Your horizontal output transistor is fine. Otherwise you'd have no high voltage and no image at all.



A broken vertical hold or vertical height trimpot can cause vertical collapse.



I replaced both vertical trimpots and no effect. Replaced the IC chip (socketed it) and no effect. Checked entire board for cracks in solder. None. Did continuity checks on every circuit. All fine. I pulled the monitor and put in another newer G07 I had on hand. Typically if I can't fix the monitor after 8 hours of work I shelf it. Probably gonna pull the Buffet chute.
 
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