Tube Amps / Music Electronics
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|previous: James Nash Hi there! I've never posted here b... -- 8/13/2000 8:41 PM||View Thread|
|8/14/2000 12:25 PM|
|Bob P||Re: HELP: High voltages on BF Bassman|
If you have 149VAC, check other outlets in the house. If you find any that are lower than normal, say 90VAC, then you have an ground problem coming into your house...call your local electric provider and they will come and fix it free. I know, it just happened to me about 3 months ago.
That may well affect your readings but keep this in mind, older circuits were designed around 110VAC, not the newer 120VAC. That alone will cause your reading to be higher that those shown on the schematic.
What model amp is it? Do you have a bias control or hum balance control? If it is a hum balance control then it is doing its job...to balance the power going to each tube thereby canceling any noise...humbucking, if you will.
If it is a bias control, the hum may be caused by grossly unmatched power tubes. Check each tube individually and, if not matched within 7-10ma, replace with matched tubes and rebias. I like them matched to < 3ma. BTW what type of tubes are in there now? If this is your own amp and you find you need to replace the power tubes, you may want to replace them with NOS RCA's rather than the new tubes that are out there.
The range of the bias pot can be adjusted by changing the bias resistor to a higher or lower value.
Hope this helps.
On another note, do you still have the old PT. I am in need of a Super Reverb PT. If you would like to sell it please directly email me the model number and asking price at firstname.lastname@example.org
Thanks again for the help on the DR,
|James Nash Bob, Gary,|