In Reply to: You found it! posted by Wayne Parham on March 01, 2003 at 22:04:30:
Back to the UL approved config, with the green safety ground connected directly to the chassis:) The negative end of the filter caps is a short buss, and is also the center point of the star ground for the signal input/output jack shield leads. With the B- floating, the jack shells achieve about 38 vRMS relative to the chassis, which disappears when a 100 ohm resistor is added between the B- and chassis ground, a la marchand.
Of note is the DC filament supply, which is effectively "floating" also...it shows something like 17 vRMS relative to B-...that has got to be a hum inducer...I will look at connecting it's "neg" side to chassis ground thru a resistor also. Shorting it hard to B- temporarily had no ill effects(at least the DC filament voltage never flickered), except the AC "riding" on the dc goes away!
So off to ratshack in the am to get a pair of 100 ohm 1 watt resistors for connecting those neg. supply ends to the chassis:) Then we'll try again "on line" in the system. Sam
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