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Hoffman Amps Forum image Author Topic: What's the bias dealio ?!  (Read 2087 times)

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Offline worth

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What's the bias dealio ?!
« on: August 29, 2012, 08:04:16 pm »
Straight Bandmaster build with Dougs 50K bias pot... can't get above 20 ma. I thought with a 50K pot , I could pretty much dial in about anything. I'm using the 470 ohm range resistor.. Heyboer Pt 350-0-350.

Offline triode

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Re: What's the bias dealio ?!
« Reply #1 on: August 29, 2012, 08:29:32 pm »
I don't know which bandmaster build you are looking at... but most of the AB763 boards use the 10k pot.

If its the bandmaster AB763, use the 10k, if you want to stick with the 50k, change the bias range resistor.

Offline worth

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Re: What's the bias dealio ?!
« Reply #2 on: August 29, 2012, 08:53:19 pm »
AB763 Bandmaster... thought a 50K pot would cover me more than a 10K.

Offline tubeswell

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Re: What's the bias dealio ?!
« Reply #3 on: August 30, 2012, 01:24:41 am »
Straight Bandmaster build with Dougs 50K bias pot... can't get above 20 ma. I thought with a 50K pot , I could pretty much dial in about anything. I'm using the 470 ohm range resistor.. Heyboer Pt 350-0-350.

Its not just about the range of the pot, its more about where the whole resistive divider for the bias supply is putting the ballpark bias voltage, and what the power source voltage for the bias supply is
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