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Old 4th Dec 2021, 12:39 pm   #56
Phantomrose1999's Avatar
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 280
Default Re: Grundig TK27 - Low audio output

Could not resist a poke at the beast, so.

Replaced C3 (22nF), which is the input cap to the main AMP. Original measured 140nf.

Removed and checked the 470p across the output transformer, and it was 1000p, did not have another so put it back

Opened the lower switch cover again, to see why record was dead with no audio, and found one wire has indeed come undone at the last switch box in the inside (motor) side. Soldered it back up and was hoping for the best..

Now for the puzzle..

Tried Play - volume is gone low again, notes

- when the volume is turned up, but play not presses, there is a loud hiss, proportionate to the volume control, like a record player, when you lift the arm and turn the volume up.

With play pressed, and no tape, touching the wires at the back of the head track 1-2, cause a very loud buzzz, proportionate to the volume control, makes me think the amp is fine.

I am wondering if the play head for tracks 1-2 has a intermittent problem ? (i did measure the resistance and shorts to ground, all same as the other track)

Now for something even more strange, when i switch to tracks 3-4, there is ZERO hiss, but then touching the other set of head wires, makes absolutely no sound. So it would seem the path from head to amp for tracks 3-4 is broken. The head measure fine, with resistance and no shorts to ground.

PS: did try record, but no audio getting through, used to work fine, until i attached the rec/play switches.
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