It looks like this could be temperature related. Doing cold tests, the Empeg always powers up in DC mode. As I've seen the temperature creep up to 54 degrees recently, I reckon this could be a factor.

I've now performed the negative spike mod, and also installed a 40mm fan. It's a bit noisy, but the sound is masked as soon as the engine is running.

In my tests, the max. temperature I'm seeing is a much more reasonable 28 degrees C.

I did have a nervous moment, when the display stopped working. Fortunately, it was just a frayed display cable, which was easily fixed. My heart was in my mouth for about half an hour, though.

Andy.