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Dynacord Powermate 1000-2 mixer amp fault - Help needed

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lalunatech
lalunatech picture

Hiya
I am repairing a Dynacord Powermate 1000-2 mixer/amp and have a question about DC blocking capacitors in the signal path.

 

I am getting a slowly dropping DC on the DISP1 node (output of I6AA op-amp) on switch-on.  This is causing the green "signal present" LED to come on on that channel which takes about 30 seconds to turn off.  It seems to be caused by a charge on C35A that dissipates slowly through R54A (1M Ohm).  

 

It seems to me, it would have been better to put the C35A on the output of I5AA with a resistor to ground.  Is there a reason why this would not work.  

 

I have checked all relevant components and power supplies and I cannot find any faults but I'm sure this is not normal behaviour.

 

Any help greatly appreciated.

PM1000 tone circuit

signal indicator

 

 

 

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lalunatech
lalunatech picture

Does anyone know why my circuit images are not loading in the post.  I know the links are good.....

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