Problem w/Vox Valvetronix AD15VT

[elixxrx66]

Last night I was running my Vox Valetronix into another amp via the headphone/line out jack which I have done a million times before. I set my guitar down for a few minutes and when I went back to play my Valvetronix quit working. I managed to get sound back out of it. Everything works fine except now the Master Volume quit working and I get no signal from the headphone/line out jack. Anyone got any ideas?