Quad 303 calibration issues

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20-Apr-2019 10:24 AM

jackdelang UK

jackdelang UK

Posts: 1

I've just installed the components purchased in the basic refurb kit.

The first stage of caliberation is looking for 67v Dc accross pins 1&9 - adjustments are made using variable resistor RV200.

However for me it is at 87 volts and the trimmer has no effect on this voltage.

 Can someone advise me please

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08-May-2019 04:21 PM

Stefaan

Stefaan

Posts: 593


It looks as if one of the transistors (TR200, TR201 or TR3 is broken. You should check them with a multimeter.

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09-May-2019 03:24 AM

EJP

EJP

Posts: 1589

Most likely Tr3 is c/e short-circuit. This can go undetected for years, as the only symptom is a bit more hum. The amplifier can work perfectly well without it.
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