Squawk & talk hum

wrongdon

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Jan 1, 2010
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wellington, Ohio
I'm working on a s&t board for a friend.It has a nasty hum as soon as i power it up. So far i have replaced all of the electrolytic caps and the amp.The amp was originally a TDA2002 but i dropped in a TDA2003.I did not replace the tant caps at C16 and C22.When i turn either pot quickly the hum goes away for maybe a second.I am testing this on the bench with a switcher and jumpered for on board pots for volume adjustment.Touching the resistors and diodes between C42 and C24 makes alot more noise.I believe the board is functioning properly aside from this,at power on i get 6 flashes then i press the test button and it goes through all the words in its vocabulary followed by a beep and then it resets.
Any suggestions ?
 
Thank you,,I'll try adding another ground or 2 to see if that helps.Currently it is just being powered up with alligator clips so maybe a more solid connection may help..


Grounding issue with the board(s)? That's the experience I've had with that problem.
 
Problem solved

I added a ground to J1 with no change , then just for the heck of it tried a different power supply.Must have been a really noisy supply as it is nice and clear now..
 
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