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Simon Gittins · 10th Feb 2023, 9:29 pm

C23 is the audio coupling capacitor; you could monitor the voltage at the junction of C23 and R19 as you bring the voltage up and then switch off as soon as you see any positive voltage if you want to prove to yourself that it is faulty. I would be inclined to replace it before powering up.
C25 is from V4 anode to the tone control, if this is leaky the tone control could burn out.
C26 is a mains aerial coupling capacitor, I suggest removing this altogether as it won't work well under today's conditions.
With these three dealt with it should be ok to power up with the variac and see if it works to some extent.

10th Feb 2023, 9:29 pm	#3
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 506	Re: Masteradio D111 C23 is the audio coupling capacitor; you could monitor the voltage at the junction of C23 and R19 as you bring the voltage up and then switch off as soon as you see any positive voltage if you want to prove to yourself that it is faulty. I would be inclined to replace it before powering up. C25 is from V4 anode to the tone control, if this is leaky the tone control could burn out. C26 is a mains aerial coupling capacitor, I suggest removing this altogether as it won't work well under today's conditions. With these three dealt with it should be ok to power up with the variac and see if it works to some extent.