I've been messing with electronics for most of my life both professionally and for fun. One rule I was taught early on is that you must always employ a current limiting PSU for any new build. Whiskers, misplaced components, dry joints and VERY VERY seldomly faulty components can be very depressing, 99% of the time the fault has always been of my own making and it's saved me on many an occasion.
For old mains transcievers and receivers I have a variac with 2 light bulbs in series. If there is a short, the bulbs burn brightly as you wind up the variac. It should be straightforward to build a low voltage version of the same, I might have a go at that.?
73s Ted?
2E0THH?
Ted 2E0THH