Valley People Gain Brain II appears to be shorting out rack.

[iampoor1]

I have a rack of 5 Valley People Gain Brain II's. I have one in particular that when inserted, causes all the meters to read 50db of reduction.  Once its removed, ever other gain brain works fine.

Anyone have a schematic/serivice manual for these? No apparent bad tracks/debris on the board. Havent started troubleshooting completly yet, just looking for some advice before another frustrating day of dealing with technology  ;D

 

[JohnRoberts]

Obvious first thing, check ps voltages... and DC on the audio in/out.  if you have working units to compare to should be easier to find where it gets lost.

JR

 

[pucho812]

have you tried that one gain brain by itself to see what it is doing? I have worked on a API rack before where if I had 5 units out of 6 in everything was fine, but the moment I had the last space filled the unit wouldn't function. This was regardless of which unit out of all 6 was inserted into slot 6. Turns out out the power supply was starting to get weak from old age and couldn't handle all 6 units in the rack. 

So do some simple tests

1. test the suspect unit by itself with the PSU. Does it work?  How dies it sound? Is it not working?
2. Test the PS with a known good unit, compare that to  suspect unit.