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In Reply to: RE: What the ?????? posted by vinnie2 on January 25, 2016 at 14:48:14
Are you sure the 10 turn pots you got are linear? What is their actual value in Ohms?
I would use a pair of dropping resistors to reduce your filament voltage if possible rather than a rheostat.
Follow Ups:
How do you tell if they are linear? I don't see any marking on them other than their value (100 ohms) and the terminal markings (1,2,cw).
You are probably right about the rheostat, but I wanted to wait until I had some idea what values to use. I can measure it off the rheostat when the hum is cnaceled.
Edits: 01/25/16
You need to verify the pot connections first. There should be two lugs that don't change the impedance between them when you rotate the control. These are the outer lugs, and the incoming AC should go there.
Next, count the turns that the pot has, then set it approximately to center. Measure the resistance between each outer lug and the wiper. With the wiper approximately in the center, the resistances will be about equal. If it's a log pot, they will be way off.
It did occur to me that if you wired one leg of the AC to the wiper on accident, you might've ended up with some of the problems you're having.
I did all that previously and set them in the middle of the range at half the number of turns so they are linearI guess. The AC was hooked to the two outside lugs.
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