[MoonHawk]

Ok ive tested the power supply of my cmoy numerous times now and it tests fine every time. Except when I plug headphones into the output and try to listen to something. The power supply seems to fail, I get a reading like -3v/6v from the caps. Anyone had this issue?

 

[Clutz]

If you have a digital camera, try taking some pictures of your Cmoy and post them. A picture is worth a thousand words, and probably a dozen or so multimeter measurements.

 

[ericj]

Yep. The resistor divider only works perfectly on paper, and only when you leave out a lot of known theory.

If those were 600 ohm headphones, it wouldn't be such a big deal. With lower impedance headphones, more current is drawn, and as more current is drawn, the 'virtual ground' will get pushed closer to actual ground.

So unless I've totally missed the plot, you're in a situation where you need a better virtual ground.

 

[Porksoda]

Quote:

Originally Posted by ericj Yep. The resistor divider only works perfectly on paper, and only when you leave out a lot of known theory. If those were 600 ohm headphones, it wouldn't be such a big deal. With lower impedance headphones, more current is drawn, and as more current is drawn, the 'virtual ground' will get pushed closer to actual ground. So unless I've totally missed the plot, you're in a situation where you need a better virtual ground.

While technically you are correct, this results in the ground oscillating, not developing a DC offset. My bet is that there is a short somewhere. Check all your soldering and make sure you don't have any solder bridges. Then, make sure you followed the schematic properly.

 

[MoonHawk]

well i just scrubbed the backside of the board a little to remove a bit of flux. I dunno if that is what caused it but It seems to have worked itself out for now

 

[Pars]

Clean the board with the purest rubbing alcohol you have (std. 70% is OK, 95% plus is better) with a toothbrush or something, then rinse it a bit (with more alcohol) and let it dry. Excess flux can certainly cause problems.

 

[leftshoe]

I'm going to declare a new law:

LEFTSHOE's first law of electronics - 70% of problems in simple circuits are caused by excess flux on the board.