Bill,
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If you haven't already, you need to isolate the A1 and A2 boards from the rest of unit.? You're making this harder than it has be if you haven't already.
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Also, earlier you mentioned measuring R44 as 18k.? It is a 20k resistor with 1% tolerance.? That is 10% tolerance.? Most of the resistors on the A2 board are 1% tolerance.? It is well documented in the 140, 180 series mainframes that when these resistors go out of spec, they can bring the whole supply down. Make sure to reference the parts list of the manual.??
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Pots and trim pots are also worth a close look on these units.? I've found faulty ones in these mainframes that cause funky symptoms.
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-Frank
Frank Mashockie