whispercf

You might try resetting it, but I suspect it needs repair. To reset, hold the class switch down and the pentode/triode switch up while powering on the amp.

I was able to make changes to my DT-25 using a Behringer FCB-1010. You have to program it first to send the appropriate CC parameters. I find it easiest to program the FCB using my computer (there are editors for both PC and Mac).