JD-990 - Computer Whine
2014-03-03 by <Lotus@...>
I have a JD-990 plumbed into a DAW that's picking up computer noise whine. No 60 cycle hum.
It has the usual EIC 3-wire plug. The whine goes away if I lift the 120 V ground which I don't like to do.
Looking at the schematic, there are five 1000 pF and two .01 uF ceramic caps across the analog ground to case ground.
With everything unplugged, the resistance from the case to the analog ground is 0.3 ohms, basically the resistance of the meter leads. Shouldn't the case to analog ground be nearly open if they're putting capacitors across it? What good would that do?
I'm thinking one of the caps is shorted. I checked the two 0.01 uF caps and they're ok, so it would have to be one of the 1000 pF parts.
It has the original caps on the power supply fwiw...
Thoughts appreciated!
Scott in Ohio