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Mind print DTC compressor Channel issues

Started by bassman1965, August 09, 2016, 03:43:29 AM

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Hello, This is my first post on this site, Please be nice and gentle
I do this sort of repairs for fun and a little extra cash. I have some background in electronics  but my day job is nowt to do with electronics now

This one is beginning to do my head in.

It came in to me a while ago for a switch problem, Fixed that the owner said that one of tone filters wasn't working
I sorted that it was a pot. He always said it works ok but does not think its working 100%

Anyway on final test i noticed that Channel B when you turned the compressor on it wasn't compressing at the same as ChA
This is done with same signal injected into both with all the tone/filters off and Compressor levels all the same.
When you check output without compressor on. Both outputs are prefect

If i turn the Trim pot TR1 on both channels full clockwise i would expect that the signal output would be roughly the same but CHB is higher. Both sets of LEDS are spot on. I knew there is some adjusters for the LED display. They are working

Pictures are
output without compression
with the compression on channel A on top trace
LED's with the compression on channel A on top part

Replaced both tubes for brand new ones

This unit has had a lot of repairs in the past and is a nightmare to work on. One main board and 3 sub boards . Lots of ribbon cables hard wired and one end and connectors at the other. Ive gone thought the hard wired connectors and remade most of them. Very hard work trying to work on and scope out and compare, I don't have brilliant test kit. I have checked that its not my scope etc

Not sure if im doing anything wrong, but im sure there is something wrong. Out of my comfort zone

please if anyone can assist