I used to have one of those! They're kinda unicorns but solid mics.I got all revved up for a tranny swap.....turns out plugging it in works too.
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May want to eyeball those diodes by the tranny. That board is getting rather warm. Maybe replace and fly the diodes a half inch off the board...
Check you varistors too. If the transformer blew on the previous owner, it tended to take a varistor with it.