If memory serves me well, the "phase 90" had 741s in it, this means power supply is applied on pins 7(+) and 4(-), so you should find 9V across these pins. ![]() I assume you know how to operate a DMM and I also assume you have good soldering abilities, otherwise you'd better take the FX to a qualified tech as per Olddawg's advice.įirst place to look is the bias circuit, at the lower left part of the schematic, you'll find a Zener diode paralleled with a normal one, measuring across it should read about 3 VDC, if not, you should try to change the Zener diode. Olddawg is right, a scope would make things alot easier, OTOH there are some simple measurements you can carry out with a DMM, especially if the reissue version you have at hand is an exact reissue.Īs to the "static" issue, this caveat is not applicable with BJTs and old op-amps built with BJT technology, you have to worry about static only when working on MOSFETs and the like ( wearing a conductive bracelet tied to GND cures this issue, anyway ).
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