Bias Pot for 100 watt Super Lead

shebbycaster
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Bias Pot for 100 watt Super Lead

« on: May 15, 2009, 05:38:37 PM »

Hi,
Anybody got a Layout drawing for where to drop in a bias pot in a 100watt Super Lead?


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cmoore
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Re: Bias Pot for 100 watt Super Lead

« Reply #1 on: May 17, 2009, 01:33:16 AM »

I am not the sharpest guy in the world, so pardon some questions. Are you building a new SL from Ceriatone, or is this a vintage Marshall? If you have a Ceriatone, did you look at their layout? It shows pretty clear on the layout where to wire the trim pot. Although, on the layout, it may appear to you to be a 50k resistor; but it is actually an adjustable pot. It kind of lies between two 10 mic e-caps. One end and the wiper are tied to ground, while the other end is tied to a 47k resistor.
I do not have a Ceriatone, but I have a 1971 metal panel. Our trim pot is actually 25k, but everything else is the same.
Good Luck


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shebbycaster
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Re: Bias Pot for 100 watt Super Lead

« Reply #2 on: May 17, 2009, 04:59:32 AM »

The Super Lead is my friend's amp and he was asking about biasing because he got some new tubes.

I missed the 50k trim pot on the layout drawing. I was looking at the 27K resistor near it.

Of course, once I looked inside the amp it was pretty obvious. His new tubes are in and biased as suggested in the Weber Bias Calculator. 450v on the plates - 38.8ma. Sounded great on the first test drive.

Sorry for the dumb question.


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