Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: gtrplayr1976 on January 31, 2017, 01:12:14 pm

Title: Blues Jr Bias ?
Post by: gtrplayr1976 on January 31, 2017, 01:12:14 pm
Is biasing with the Hoffman board the same as with the original ? On the original I measured voltage drop between the OT CT to the plates.
Thanks !
Title: Re: Blues Jr Bias ?
Post by: sluckey on January 31, 2017, 01:25:01 pm
You can do that. But Hoffman included two 1Ω resistors on the board to make monitoring bias current much easier and safer.
Title: Re: Blues Jr Bias ?
Post by: gtrplayr1976 on January 31, 2017, 01:26:56 pm
Quote from: sluckey on January 31, 2017, 01:25:01 pm
You can do that. But Hoffman included two 1Ω resistors on the board to make monitoring bias current much easier and safer.

Thank you ! What's the procedure for that ?
Title: Re: Blues Jr Bias ?
Post by: sluckey on January 31, 2017, 01:33:41 pm
I don't know that there is a procedure specifically for that amp. Use this...

http://www.duncanamps.com/technical/lvbias.html (http://www.duncanamps.com/technical/lvbias.html)
Title: Re: Blues Jr Bias ?
Post by: gtrplayr1976 on January 31, 2017, 02:16:26 pm
Quote from: sluckey on January 31, 2017, 01:33:41 pm
I don't know that there is a procedure specifically for that amp. Use this...

http://www.duncanamps.com/technical/lvbias.html (http://www.duncanamps.com/technical/lvbias.html)

Thank you !
Title: Re: Blues Jr Bias ?
Post by: purpletele on January 31, 2017, 02:40:53 pm
Quote from: gtrplayr1976 on January 31, 2017, 02:16:26 pm
Quote from: sluckey on January 31, 2017, 01:33:41 pm
I don't know that there is a procedure specifically for that amp. Use this...

http://www.duncanamps.com/technical/lvbias.html (http://www.duncanamps.com/technical/lvbias.html)

Thank you !



GTplayer1976,

I just went through the procedure and referenced Doug's article on biasing amps

http://el34world.com/charts/fenderservice5.htm (http://el34world.com/charts/fenderservice5.htm)