Pepe,
Is the source side motor actually moving, or is it just the brake being released allowing the motor to freewheel?
I suspect bad motor caps for the take up function (both motors). I do not know this model deck, but do know some R2R machines use a two step voltage approach and sometimes the caps driving the higher voltage go bad, while the caps for the lower voltage still work (enough to allow supply, but not take up).
MG