It sounds like you have the battery/tuner/VU button is pressed down. Check to see if the switch is not shorted or constantly depressed. The left meter is dual VU/Battery meter and will deflect to reflect battery voltage, max if AC.
As for mechanism continually clicking, it sounds like a mechanical problem, possibly an error in the rebelting or other issue not allowing the deck to reset. Decks sometimes also make that noise if it's run in reverse due to wrong motor (CW instead of CCW) or improper belt routing, although in the case of an M70, unlikely since it's pretty self explanatoy. On the other hand, I've noticed that the M70 deck is very sensitive to friction and jamming of all the various levers and slides. It needs to be completely clean, free movement and lubed where appropriate, and rust/corrosion cleaned off for most reliable operation.