hi there mx5050 question

[jdm5149]

hi john from nyc here. i recently purchased 2 mx5050 8trks for $350 a pc. i've had to replace the pinch rollers so far. my question is that on both machines, it seems channel 1 does not get any signal. on machine 1 , when in input mode, i get no movement on the vu mater when i switch to either test tone.. on machine 2, i get no signal with the srl button pushed in but when i release it i get signal when using the trim knob. any suguestions?? also, by switching the 2 & 3 pins on the xlr connectors, will that make it compatible with my newer balanced gear.