-=> Roy J. Tellason said to All
 -=> about "POWER SUPPLY" on 10-25-03  04:06.....

 RJT> Beats the heck out of me what parts I might be wanting to look at
 RJT> next,  to the extent that I can with my eyes in the shape they're in
 RJT> these days. 

There should be a couple of large capacitors rated at about 400v,
IIRC these should have about 150v on them when the unit is
powered up. Discharge these first before continuing with tests!

Some of these power supplies have a mains fuse on the PCB. While
it appears at first to be a damn stupid place to put a fuse, it
does prevent someone replacing it with one rated for automotive
use (10A or higher).

You should first test for continuity from mains input through the
power switch and rectifier diodes to the big capacitors.

Check the two transistors that feed power from these caps to the
transformer. Note these are high voltage transistors, usually
rated at 600v peak if you are thinking of replacing them. A
digital voltmeter usually has a diode test position which is
fine for checking the forward and reverse voltage drop through
the junctions. One of these transistors may have gone open
circuit.

Connect power, measure voltage across the big caps. Should be
about 300v total IIRC. Check for high frequency signal from the
power transistors to the transformer - caution: HIGH VOLTAGE.

Beyond that, you're getting deep into more or less unknown
territory.

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Read the manual?  Doesn't it come in automatic?
___ Blue Wave/386 v2.30

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