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G-5700 staying in Protection

prose116

prose116

New Member
Hi All,
Picked up a G-5700 recently. Left channel was cooked, replaced all caps on 2980 board and cleaned off the old glue tested and replaced defective resistors and transistors on left side. right side resistors and transistors seem to test ok. Plugged into DBT and powered up, Safety light flashed on and off and relay clicked twice.
New filter caps installed . I have read many posts and understand that these boards are a nightmare.
Any help would be appreciated as I am not by no means a expert with electronics, But I do enjoy working on them and learning.
Thanks in advance
 
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Did you replace the DC offset and Bias trimmers, essential on these amps when they have had a failure like that.

Also need to adjust the DC offset and bias.

Start there and let us know how you get on.
 
replaced 4 trimmers but unable to adjust DC.
15 vdc on left side and 1 vdc on right side
nothing changes when I try to adjust
 
Is there any reading for bias? Is that adjustable?

The offset is indicating an issue, you will have to methodically go through from top to tail of that driver board.
Starting with the emitter resistors of the output transistors and then working back up the circuit towards the front end.
I suspect you will find some open or shorted Zener's and possibly some Hi-Ω resistors.
Be careful working with the F2980 board, the foil traces are very thin and easily damaged, and often in a way you cannot see with the naked eye.
 
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