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Audio Research VT200 Biasing Schematic ETC.

Since Audio Research Corp. will not provide a PCB schematic for the biasing of my VT200 behemoth I would request anyone with a circuit board scan and/or schematic to come forward. I hesitate to do this with merely their 2 page biasing instructions as I also know any tech, even at ARC, would rely on a detailed image of the printed circuit board, component values, test points and detailed procedure.

Thanks,
John
dischief
jea48
4,425 posts
 
Dischief,

Not sure about the VT200 but the biasing of a VT100 mark 1&2 can be a bear if changing the small signal tubes along with the power tubes.If done improperly the new tubes and or the amp could be damaged.

My understanding changing the power tubes only is some what simple....

You might want to give ARC a call and find out if the VT200 bias like the VT100 mark 1&2.

http://mycollins.net/audio/artube1.html
http://mycollins.net/audio/artube1.html
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spinaker01
491 posts
 
Biasing the small signal tubes is not as bad as it seems. The process is a bit finaky until you get comfortable with it, but I can do mine in about 15 mins with a single digital volt meter. The trick is to check the 60v rail voltages, and switch 2 tubes around at a time to get them as close as possible. This will make the lower mAmp adjustments easier whilst keeping the 60v rails even on the upper and lower traces. Albert does a good job of describing the process on the link. The ouptut tube bias is really easy, but keep in mind there is over 400v at this resistor!
hifigeek1
770 posts
 
Re VT-100 mkl and mkll. I prefer to use 2 volt meters. Still kind of a pain. I suggest people get some grabber test leads as it's safer rather then just using probes.
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