Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: blown240 on October 18, 2011, 10:26:05 pm

Title: Volume Pot Testing
Post by: blown240 on October 18, 2011, 10:26:05 pm

Is it weird that the resistance in my volume pot is highest when the shaft is centered?   If I put my meter on the center and either side, the readout goes from 0-250-0 as I sweep thru the range of the pot. Seems like it should go from zero to its highest point.

Will this cause problems?

Title: Re: Volume Pot Testing
Post by: Danskman on October 18, 2011, 10:48:20 pm

Did you measure it apart from the circuit? If not, could be due to the circuit itself; please post schematic. A pot should not react by itself like the one you describe.
BR,
Danskman

Title: Re: Volume Pot Testing
Post by: stingray_65 on October 18, 2011, 10:49:32 pm

Where did you get the pot?

What is its stated value?

Sounds like some sort of balance pot.

Get a new one.

Title: Re: Volume Pot Testing
Post by: blown240 on October 18, 2011, 11:20:04 pm

Ya I tested it by itself, and got a new one.

Thanks!

Title: Re: Volume Pot Testing
Post by: sluckey on October 19, 2011, 06:48:50 am

Are you using that Fluke T5-600 Electrical Tester? Specs say it only measures up to 1000 ohms. It's a continuity tester, not a proper ohm meter.

Title: Re: Volume Pot Testing
Post by: blown240 on October 19, 2011, 11:01:26 am

no I bought a DVM that I am using.  Its a cheap one, but seems pretty accurate.

Title: Re: Volume Pot Testing
Post by: stratele52 on October 19, 2011, 03:51:43 pm

Don't forget volume pots are most of the time "audio" type, or logarytmic. Resistance are not equaly each side.

Other  ( almost all)  pots are "B" linear

Here , you'll see how to mesure "audio "pot. if not sure . Look a the bottom of pages

http://www.ladyada.net/library/metertut/resistance.html (http://www.ladyada.net/library/metertut/resistance.html)