9 May
1999
9 May
'99
8:02 p.m.
Dave Dameron <ddameron(a)earthlink.net> replied about my IMSAI PSU woes:
If the voltages checked out without a load, look for a
very
good short somewhere.
The incoming AC was measured at 120.0 VAC. The primary has taps for
nominal, -10%, and +10% input. When I received it, it was apparently set
for -10%. I say apparently because the transformer doesn't match the one
in the IMSAI manual. The no-load DC voltages are expected to run high, but
these were even higher: 25V vs. 18V, 11V vs. 8V. I switched it to the +10%
tap, and now under some load (CPU, one memory card, front panel) the DC
voltages are very close to the nominal values. So I suppose this could be
indicative of shorted turns in the primary.
The 5 Amp line fuse didn't blow?
Nope. But the transformer emitted a foul stench after a few minutes. It
wasn't hot enough to be painful to touch, but it was close.