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Some very strange issues with a Sony TC-K850ES

9

928GTS

Active Member
I've recently received a TC-K850ES that was in need of a mode belt. I have everything back together and I have a mech issue or two to fix but the electrical issues are bothering me quite a bit. The issues are as follows:

1) Noticeable distortion on the right channel during playback. Right channel VU is pegged. I don't think it's coming from the heads as the VU still pegs if I disconnect them. If I disconnect connector CN563 from the main A board the right VU no longer pegs. CN563 connects to a connector labeled "No. 804" (I believe) which is located just below D801 and D802.

2) I'm unable to hear a line in source when the source selector is set to "source". If I switch to "tape" I can hear that it's making its way onto the tape but the deck isn't fully erasing what was on there before. Sometimes if I switch to "source" I hear a very short snippet of the line in before it's muted to nothing. I am able to vary the line input through the main recording level control.

Any ideas would be greatly appreciated.
 
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Do you have the deck connected correctly to the amp? Deck output should go to "tape monitor in". Deck input should go to "record output".
 
I'm not using it with an amp for the moment. I'm just testing it through using headphones and using an external source to input into the deck for record testing.
 
The clue here, I think, is that it isn't erasing fully. Check the power supply voltages. Check for cracks in the board if it was shipped.
 
The annoying bit is that the deck was working for a short while after I had finished servicing the mech. I don't think it has anything to do with the heads or related playback circuitry because I'll disconnect the heads from the main board and the VU meter on the right channel is still maxing out. However, when I disconnect CN563 the VU meter returns to zero as it should. I'm having trouble figuring out what CN563 connects to on the secondary (smaller) main board and what voltages (and functions) it carries. The trouble seems to be coming from there but I'm not sure where to take things next if I don't know what that connector does.
 
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