I recently picked up a Fluke PM3394B which was refusing to display any traces, or trigger on any input, but at least the digital side of things looked to be ok.
Turns out the the analog board had various vias which had become disconnected, and a couple of broken traces, and fixing these had lead to a functioning oscilloscope - result!
The dodgy vias are very small diameter, and may be laser cut (not sure, but it's a mid 90s Philips design, so whatever they were using at the time). To sort these, i've traced the missing signals to other places where the vias were working, and used connections between these points to resolve the missing signals. It's not the neatest, but it's working. Here's a shot of the board with it's extra wiring:
If the vias were larger, i'd have pushed a wire through and remade the connection that way. Given these are too small, and the dodgy ones are blocked, is there a better technique? Will drilling out the holes (assuming I can track down a thin enough drill bit) work, or will I just in reality end up doing more damage, and I should stop at this point as it's working?
BTW, the failure seems to be caused by thermal cycling. This scope had two extra daughter cards for TV and external sync options, and the trace and via failures were under these boards, so i'm speculating that extra heat or lower airflow from these boards has caused thermal issues over time with the board.
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