Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: g-man on March 10, 2023, 12:41:07 pm

Title: JTM45 bias
Post by: g-man on March 10, 2023, 12:41:07 pm
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Title: Re: JTM45 bias
Post by: HotBluePlates on March 10, 2023, 12:50:24 pm
... one tube was redplating. ... I can bias right at 34 mA with the bias pot at minimum. ... Should I change the 10K pot to 50K?

If you want to cool off the tube, you need a more-negative bias voltage.  You can get there by making the 220kΩ resistor smaller, or the 82kΩ resistor bigger.

A 50kΩ pot would give you a little more wiggle room because it increases the total resistance of the Pot+82kΩ.  But lowering the value of the 220kΩ will be more impactful.
Title: Re: JTM45 bias
Post by: g-man on March 10, 2023, 01:32:25 pm
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