#1
I plugged my OS-2 into my Valve King 112 on the clean channel. Bypassed, i got no sound. Engaged, all I got was an intense high-pitch whine. Should I have tried a new battery?

Or is something else wrong?
#2
Try a new batter before you do anything, and double check that you have your input and output right! may seem silly but ive accidentally done that without a clue whats wrong

But the battery may be (most likely is) dead, ive had similar issues there too.
Ball Custom Mark I

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#3
^^
i agree, it might sound stupid, but one time i actually mixed up my ins and outs and the same thing happened