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Old 3rd Nov 2021, 10:27 am   #9
Phantomrose1999
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Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 261
Default Re: Grundig TK27 - Low audio output

Thank you Chris for the informative answer.

I did some more measurements and found the low HT is still the problem, i suspect.

1) original, HT 222v

2) Replaced bridge with 4x diodes, HT 242V (sound louder)

3) Replaced EL95 from a good working unit, HT 252v after warm up, much higher closer to 297v at first power on (sound louder)

4) Measured AC input to rectifier is 202v AC !!!!

5) Found the Rectifier side fuse had 2.7v drop, replaced it, no difference.

So i am wondering why the AC output from the transformer is so low.

When installing the new rectifier diodes, i noticed a black wire floating around that looked like it came from the transformer. Taped it up and let it be.

looking at the schematic there is a black wire from the transformer, but how could it work if not connected ? unless power was being routed through the motors coils to the transformer on the return line ??
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