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Old 9th Nov 2019, 6:33 pm   #59
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 348
Default Re: Vintage Radio and Phonograph cutter schematic

Originally Posted by ms660 View Post
Originally Posted by Levente View Post
I did tie the pin 3 and 4 together to chassis. Unfortunately no sound is coming through the speaker or no sound on the external speaker plug either.

Hum is reduced and no any other issues but the sound has gone...
It will kill the sound, that's part of the test, if shorting those grids to chassis has got rid of the loud hum you had with the volume controls turned down then remove the short from one grid and see if the hum gets loud again (volume controls still turned down) if it doesn't then remove the short from the other grid, that should tell you which grid the loud hum is coming in on, let us know which grid it is, ie: pin 3 or pin 4.

Aaaa okay.

With the volume pot down, now there is not much hum like before (when the other capacitor was in place) I did change the 8B cap.

If I turn up slightly the volume, then I can hear the hum and with the volume control the hum increasing and decreasing.

If I ground pin 4 the hum has gone. If I remove the short hum comes back.

If I ground pin 3 does not seem to change anything at all. Same results grounded or not grounded.

Thanks for helping me on this.
Levente is offline