I'm building a VFO..
So, first I do the power supply. I put a transformer in the chassis, then dug into my junk boxes for a set of suitable diodes for a bridge. I have 4 matching 1N255's. Rated at 380 volts @ .4 amps, they will handle what I'm building and since they are in the junk box they will do quite nicely.
I've never used Stud type diodes, but no problem, mount 2 of them on them on the chassis and two of them on stand offs. Mount a choke and a pair of cardboard wrapped axial lead electrolytic capacitors.
I'm sure someone already knows what I did wrong, but to continue, I wire everything up.
Then, before I go any farther, I smoke test the power supply. I should get ~ + 185 volts, but instead I have ~ -70 volts
. So I do a quick visual to make sure I have the meter connected right. About that time ...
Sounded like a cherry bomb. One of the caps exploded. Oil everywhere. I shut off the power strip. What did I do wrong???
I assumed (without checking) that the stud end of the diodes (where they mount) is negative which would make the chassis negative. Wrong, the stud end is positive. Which means I wired up the electrolytic caps backwards.
Clean oil off the chassis. Replace 2 blown electrolytic caps. Mount all four diodes on standoffs and make double sure the chassis is negative. Now it works.
So.... If you want to know what happens when you push 185 volts backwards through an electrolytic cap rated for 450 volts, you don't have to try it, I already did and I can tell you it turns them into cherry bombs.
Don't Try This At Home.