[duncanlowe]

With the 'put a bigger fuse in' theory I also while still a trainee saw a fail. Another but supposedly more experienced trainee built a power supply. Connected and switched on but the glass fuse popped. So he tried the next size up with the same result. The next size up again didn't so much pop as explode leaving only the end caps and vaporised glass. To his credit he did stop at that point and ask me what I thought might be the problem. I pointed out that connecting the secondary to the mains and the primary to the rectifier / regulator probably wasn't wise. I'm guessing it produced a nice HT supply for a fraction of a second......