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Old 22nd Oct 2020, 7:39 am   #68
Station X
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Location: Ipswich, Suffolk, IP4, UK.
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Default Re: Motorola 5A7A dead.

R20 is connected to pins 1 and 5 of the 1U4.

I'd leave C10 well alone, low value capacitors seldom give trouble. Chances are you're measuring resistors in parallel with it. Only way to be sure is to lift one end.

I'd replace R4, as it's drifted high in value, and see what that does for the filament voltages. If no joy replace the rectifier E2 with a silicon diode such as a 1N4007, marked end towards R4. However you'll then need to increase the value of R4 to compensate for the reduced forward volt drop of the diode when compared to the rectifier.
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