K7400 Exploded Trace From Not Being Secured

zenomorp

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Donor 2015
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Got this K7400 in on a trade yesterday. Was told it was working fine but it wasn't secured in the frame and when the machine it was in got moved, it slipped out of the frame and there was a "pop" when it was powered on. It still worked, but the image was "wavy" and after a few minutes, the tube would start to get discolored like it needed to be degaussed because the thermistor was out of circuit.

Put it on the bench today and quickly discovered the issue. A trace that runs through D102 as part of the degauss circuit and ending up at the degauss thermistor/relay was blown apart. Had to replace D102 as it was completely shorted (the image was "wavy" because half of the rectification circuit was open due to the exploded trace - I'm surprised to powered up and worked at all). After replacing the shorted D102 from a donor board, fixing the trace with a piece of desoldering braid, and doing a little reflow in the area (especially on the thermistor/relay), it's back to working great.

Got the B+ set to 117vdc via the light bulb test (will need to be readjusted later due to this chassis only having a partial cap kit installed which I'll have to complete and then re-verify the B+ after that), let it run for about 10 minutes, and it seems to have no latent issues. I'll finish the cap kit, do a full reflow, clean it up, fix up the neckboard, and it should be at 100%.
 

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