1943 feedback sound 'warmup' issue

ThomasM

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Hi guys, my 1943 has developed a 'warm up' buzz. I turn it on and it's giving feedback noise (buzz) and the monitor isn't syncing. After awhile, the buzz stops, and the noise/lines on the screen continue - and eventually end (or if I unplug and plug it back in), then works fine.

I just assumed that it was a monitor thing - and it has been on my list to swap/restore the monitor. Today, I did that - and the buzz continues.

I'll research more - but any immediate thoughts on these things are typically a pcb board issue or power supply?

Thanks
 
It could be a ground issue or possibly capacitors going bad on the actual pcb. Look close at the caps near the audio section and see if you notice any that have vented or swelled up.
 
How old is your power supply? You could be getting filter noise bleeding through.
 
Thanks guys - yeah, the power supply has been changed out, but it's been sitting for awhile in storage, so it may be time for a new one.

Given it's a JAMMA board, I may swap in another board and see what happens, swap the fuses, do some testing of the power supply and troubleshoot more carefully. Hopefully not a PCB issue on the 1943 board.

Will report back - excited though, as I just swapped out the old burn-in monitor with a brand new tube swap and freshly capped K7000 chassis so that picture should be nice and crisp!

Cheers
 
If it is the pcb, it's probably the capacitors, there's only 5 or 6 in the audio section so it would be a lot less $$ than a power supply. The pcb doesn't cost very much either, normally less than $100. One more simple thing to try is cleaning the jamma connector or maybe just reseating the connector.
 
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