Is there some way to get snap-in capacitors with a 10mm lead spacing onto boards (ie vintage amps) with 20mm spacing? I know I can get a mounting ring and run leads from the cap to the board, but I'm looking for other ideas.
Solder about an inch or so of wire to each lead such that they extend sideways from the capacitor. Then carefully fold in the connections and bend the wires so they fit in the holes. Finish by soldering and cutting excess wire.
Leaving the cap sitting up on its pins wobbling? For reliability, you really want the cap flush against the board so it can't wiggle. Or clamped. If you want to run wires, then consider placing the cap on its side, lying on the board.
