I just bought a used Egnater Tourmaster 4100 head and it has problems.1) channel 1 overdrive has barely any audio passing through it.i can hear the eq and gain and volume works for this channel but it sounds like its shorted out enough to barley let sound go through. 2)I noticed that the tube buffered effects loop only lets half the audio through it with send and return knobs on back maxed out on 10 both. 3) I noticed with master volume up half way and all 4 channel volumes turned to zero if I tap the front or sides of the amp with my finger it makes a tink sound(through the audio path out of the speaker) wich I think is microphonic tubes somewhere. Does anyone on here have any info about this amp? I really need the schematic if possible.