In search of some help/insight...my 4100 suddenly lost channel switching ability...none of the LED's light up and the front panel push buttons do not work (footswitch is the same)...I have Clean/Vintage 1 and all dials work for that channel...the master section also seems to be working properly...not sure how the channel switching on this amp works, relay? Diode? It was all of a sudden so I assume it's not much...any help would be appreciated...PS:way past warranty so I am looking to fix the issue myself...tks in advance!