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Old 30th June 2004, 04:08 PM   #1
sbelyo is offline sbelyo  United States
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Default CMOY Help?

Hello...
I seem to have a problem getting a new cmoy up and running. I built one two weeks ago and it was fine. I sold that one and went on to build another and I just cant get it running.

Symptoms:

Extremely low Volume when using line out or volume control from source.

When opamp is under load the voltage varies greatly from + to - more that 1 volt.

Troubleshooting steps:

Replaced all resistors in amplification section and bypassed input capacitor. No change

Replaced capacitors in power supply from 1000 uf to 220 uf. No Change

Tried 3 fresh from package opamps. No Change

Desoldered everything in amplification section and resoldered everything with absolutely no cold joints. No change

The only things I haven't changed are the main board, the 5.6K resistor limiting the current to the LED and the 4.7K resistors in the power supply. I suspect maybe a ground problem. And I also noticed that when the power is shut off i can still hear the source. Everything is set to the spec values in the design except for the 5.6K resistor limiting the LED.

Any thoughts
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Old 3rd July 2004, 09:09 AM   #2
Mr. X is offline Mr. X  United States
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Location: Richland, MI.
First clean all of the flux off the board.
Then visually inspect it with magnification.
Even the slightest solder bridge cause cause you to pull your hair out with those little amps.

Last but not least consider starting over. Building another amp and then coming back to the problem one is a for sure way to get a new perspective.
On projects like this it is very easy to get caught in a situation where the problem is right in front of you but you don't see it cause you have been working with it to much.
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Old 3rd July 2004, 10:14 AM   #3
matjans is offline matjans  Netherlands
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can you post a schematic ?
are you building it on veroboard or ar you using a pcb ?
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