Bias pot wattage.

[ER]

Having trouble finding a 10k bias trim pot, I have a 1/4 watt Phier 10K trim pot, and a 7.5K 1/2 watt trim pot. Will either of these suffice for a 100 watt 6ca7 amp with a 60 volt bias tap or do I need something more heavy duty?

Thanks, Erik

[fp2000]

think about it, even if you had all 60 volts on the 10k pot, then it would be dissipating 60*60/10000=0.36 watts. I personally wouldn't use anything less than half a watt. I am not sure what the wattage of the regulas bias pots are. Try tubesandmore.com, they have what you're looking for.

[ER]

I found a couple unmarked 10K multi-turn pots in my junk box that should do the trick. Measure first buy later….

I don't know where to find the type of bias pots that are shown on most of the layouts.

[dimitris]

Hi, these sellers have that pot:
http://www.tubesandmore.com
http://www.turretboards.com
Search for Fender bias potentiometer.

[dave g]

think about it, even if you had all 60 volts on the 10k pot, then it would be dissipating 60*60/10000=0.36 watts. I personally wouldn't use anything less than half a watt. I am not sure what the wattage of the regulas bias pots are. Try tubesandmore.com, they have what you're looking for.

In general, this is incorrect.

I've never seen a bias circuit that simply puts all the voltage across a 10k pot. That's just a bad idea. Usually it's sandwiched in between a couple (larger) resistors whose values are chosen to limit the bias pot's range to a usable region. Or it forms part of a larger resistor divider network and just a small fraction of the voltage drop is actually across the pot itself.

The average trim pots that you see in just about every fixed biased guitar amp out there are rated around 1/10 of a watt. So you're fine. I suggest you copy an existing bias circuit (how about a 100 watt superlead?)

[fp2000]

Dave G is right, I was just trying to be on the safe side.

[ER]

I'm using a #183 style bias with a 22k tail.

Thanks Dimitris, I don't know how I couldn't find those before, I never looked for fender parts I guess. I ordered my chassis from Turretboards and my order from tubes and more shipped tuesday. Not worth paying shipping on a single part

I'll use those next time.

[glasman]

Mojotone sells the 10K CTS bias pots. I use them for my Zingaro amps.

My ONLY issue is they are NOT WW, but carbon. Have had no failures, but would prefer WW. With a 60V bias tap, 2.2K series resistor, and 22K tail, the range is about -60 to - 40 volts (from memory).

Gary