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Restoration73 · 17th Jul 2017, 2:35 am

A multimeter may not give anything more than a static check on a semiconductor. As already mentioned the fault may be due to problems with the driver or power supplycircuitry. If the amplifier still functions, you may be able to fault find without the destructive effects by reducing the mains voltage or limiting the DC current to the outputstage using a wirewound resistor, e.g. 47 ohm 11 watt or similar. Faults caused by instability may need a signal source and oscilloscope to observe.

17th Jul 2017, 2:35 am	#11
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Quad 303 repairs. A multimeter may not give anything more than a static check on a semiconductor. As already mentioned the fault may be due to problems with the driver or power supplycircuitry. If the amplifier still functions, you may be able to fault find without the destructive effects by reducing the mains voltage or limiting the DC current to the outputstage using a wirewound resistor, e.g. 47 ohm 11 watt or similar. Faults caused by instability may need a signal source and oscilloscope to observe.