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Old 3rd Nov 2021, 7:03 pm   #17
DMcMahon's Avatar
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 4,982
Default Re: Grundig TK27 - Low audio output

Disconnected my transformer black wire from terminal 5 for comparison purposes.

Basically got very similar voltage results to you, 202VAC into the bridge rectifier and HT of +239V BUT in my case the playback sound did not noticeably change at all, i.e. still good volume and good quality. This ties up with my previous experiences where the HT voltage can be quite dramatically low and everything still appears to function normally.

Hopefully in your case when you reconnect the black transformer wire it will restore your sound to good volume but based upon my test I am not confident that it necessarily will.

The heater filament supply to the relevant valves measured 5.88V with the black wire disconnected, very hard to see how this happens ?

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