[R-390] query re ground loop (OT)

[Roy Morgan]

On Jan 30, 2011, at 6:57 PM, wli wrote:

> I have a strange problem on my stereo. Loud interference-like mid- 
> range pitched (not 60cps) hum when plugged in using 3 wire plug.  
> Turned off all the dimmers in the house: hum persists.

Do the standard trick: stand at the circuit breaker panel having  
arranged a way to hear the offending sound.  Turn off every breaker  
one at a time to locate some culprit.  The list of appliances and  
other things that can cause such troubles is too long to remember, but  
it included washing machines!

>
> The offending receptacle itself is grounded properly insofar as I  
> can tell.

OK , but maybe not. A DMM will help you, or spend the modest money for  
an outlet tester. I suggest one that has the GFI outlet test button.

Good luck!

Roy

Roy Morgan
k1lky at earthlink.net
K1LKY Since 1958 - Keep 'em Glowing!