Power supply failed - Astron PPS-4A - any ideas?

[Jeremy D. Grotte]

I've got an older power supply, an Astron PPS-4A (SN 97431045), 0-16v, 0-4a,
CV/CC, digital indicators, yada-yada. Main PCB has a ZSDT-CT/01 and both
volt/amp pcb's are labelled Z-DPM/01. I could throw it away and buy
something 'new and improved', but it was my very first 'real' power supply
(vintage '97?, I know...not that old) and I'd like to keep it around, mainly
for sentimental reasons.

Anyways, it's dead. I can power it up, set the voltage, set the
max.current, and I can set it thru the full of range of both.
When I turn on the output, the internal voltmeter and an external meter
readings indicate .6v (a diode drop) and no current.

I've pulled the unit apart, checked for the obvious (and some not so
obvious?) burnt parts, bad solder joints, reseated all the connectors I
could see, etc, etc. No luck.

Anybody have a good schematic/troubleshooting guide, hints, ideas for this
unit?

TIA...
JDG