Hartke HS1200 - what keeps the bias V in the middle ?

[jeffects]

I'm going to assume the bias is set by VR202 since it has the word "idle" stamped next to it, and that turning it all the way to left is the "coldest" setting. Is this correct?

[g1]

If it says idle, it should be the bias pot. But left is not always coldest, there is no standard. Some are opposite. Try with your limiter lamp till you find out if counter-clockwise reduces bias.