Orange TH 30 switch on issues

[blashyrkh]

I have a Orange TH 30 at home. So my amp is switch off at the moment, in stand-by mode and is also on the clean channel. But I switch it on and set it on half or full mode after about 30 seconds, you hear the distorted channel very silently... I switch it to the distorted channel, back to clean and then it works.

What could be wrong?

Thanks