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Old 9th Nov 2019, 3:25 pm   #55
ms660
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Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 10,338
Default Re: Vintage Radio and Phonograph cutter schematic

For instability and hum I would check the HT filter capacitor (electrolytic)

If no joy then short the control grids of V5 to chassis, that's pin 3 and 4 of the 6SC7 to chassis and note any difference.

Lawrence.
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