replacement transformer wanted for IMSAI power supply

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Mon May 10 09:14:27 1999

At 08:02 AM 5/10/99 -0000, you wrote:
>Dave Dameron <ddameron_at_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.

It doesn't sound like it, a shorted turn would have a large effect with any
primary tap, even with no load. Yes, the +10% tap is good, if you run the
120 +10% tap from the 120Volt line, you will get about-10% output voltages,
OK unless you have a fully loaded system. I routinely use a large 24 Volt
CT transformer as a "buck" transformer to get 120-12Volts and 120-24Volts.
for linear power supplies.
Primary: (COC.= winding)

+10% -C||
nom. -O||
-10% -C||Secondary windings here
      O||
      C||
neut -O||
-Dave
Received on Mon May 10 1999 - 09:14:27 BST