I somehow don't quite understand: You're getting both +15V and -15V at the opamps, but you assume that something is wrong with the power supply because the test point in the supply itself doesn't give you -15V? I would guess it's probably the wrong test point then.
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Re: [vintagesynthrepair] CS-70m power supply issue, -15V rail is dead
2013-07-20 by Malte Rogacki