| heater-cathode hum? [message #40480 is a reply to message #40476] |
Sun, 02 March 2003 16:21  |
Sam P.
Messages: 307
Registered: May 2009
|
Grand Master |
|
|
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
|
|
|
|
Posting Rules
Members
Search
Help
Register
Login
Get a T-Shirt!
