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Old 9th Nov 2019, 3:38 pm   #56
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 348
Default Re: Vintage Radio and Phonograph cutter schematic

Originally Posted by ms660 View Post
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.


Flipped the chassis up and started to poke around. Before that checked in the dark, no spark I saw.

Then just as you said Lawrence, the second filter electrolytic cap which +ve has 3 leads connected as soon as started to move thos leads or poked on that cap it is definitely something there.

For some reason now up side down it does not squealing. But the hum is there.

I only have a very small size new electrolytic cap.. would be that OK to try? It is not a massive can capacitor but rated 22uF 450V and designed for low profile PSUs (modern ones) ?

If this is OK will try this first then shorting the pins on the 6SC7 or shall i just do it anyway? Thanks a lot Lawrence.

Last edited by Levente; 9th Nov 2019 at 3:52 pm.
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