Semi-Customized DAC Part II (in which we hit a roadblock and ask for help)
by, 04-24-2013 at 08:44 AM (1375 Views)
Disappointing news from the trial run (no chassis or ribbon conductors, just everything laid out and hooked up with regular wire for testing):
Everything is soldered and connected, with a 1A fast blow fuse in the IEC inlet. When I plugged it in this morning, the transformer (an R-core transformer I purchased separately from the boards) got piping hot to the extent that I smelled plastic and was afraid to leave it plugged in long enough to listen to anything. One thing I did, though I am guessing it wouldn't cause this, is that I twisted the secondaries of each color together before soldering them individually to the appropriate contacts on the PSU PCB.
The fuse is intact and all the lights on the PCBs still went on the second time I plugged it in (though the solder contacts under at least one of the PSU capacitors also got very warm, and a capacitor or two was also warm). But the transformer again got way more hot than I think it should be, in half a minute or so getting so hot that after I unplugged the power it was still too hot to comfortably touch.
I'm supposing this is (very) wrong. Any notion of what I might have screwed up?