I'm having the same imbalance problem on my RS1500. It happens on the 4 track head and apparently not on the 2 track head although I have to do more extensive testing. Imbalance can be as much as 3dB based on the meter readings. I cleaned the heads but the problem is still there. The tech who sold me the deck assures he checked for alignment and that it must be a head cleaning issue. He has been very helpful and offered that if I can't correct the problem I can send him the headblock for him to align it.
If I take the headblock off, however, I might as well send it to JRF magnetics for a full service. What do you think?
The deck is in very good condition mechanically from what I can tell. Runs very smoothly and silently and most of all, aside from the balance issue it sounds very, very, good. However if the balance issue arises from a misalignment head, well, it can only sound better right?
Xavier Cortes