Adding a bias pot to a Valveking 50 watt single 12 amp

Bill Duncan · From: Lenoir, North Carolina, USA

I have a ValveKing 50 I want to be able to set the bias. I have not been able to find a schematic for it. I found a heavy duty 390 ohm resister coming from the standby switch I believe controls bias, but I am uncertain. Any help in adding an adjustable bias pot would be appreciated.
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You can observe a lot just by looking

Fred · From: Amesbury, MA

https://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-Valveking-112-Schematic.pdf

Here's a schematic. The bias voltage is set by a voltage divider comprised of R211 and R205.

Be careful soldering/desoldering the pc board. It's pretty easy to mess up the traces.

Fred

Bill Duncan · From: Lenoir, North Carolina, USA

Thank you, Fred.
_________________
You can observe a lot just by looking

Bill A. Moore · From: Silver City, New Mexico, USA

I downloaded some "Mod" information when I picked up a VK 2-12, but "loaned" it to a friend before I could do anything. The section on an adjustable bias may be what you want!
https://web.archive.org/web/20151113040720/https://ultimate-guitar-valveking.wikispaces.com/Amp+Mods+-+Electronics

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