I recently went through quite a battle with the DC offset on my Yamaha R -700 (which as no offset adjustment per say). When I first got it (in January) the offset was a pos. 32mv on the left and a neg. 50-60mv on the right (with a fair amount of fluctuation). Well, I figured that this was somewhat acceptable and, as such, put the rcvr into service after cleaning the controls, tightening the chassis screws, and performing a couple of internal adjustments (as per the service manual).
However, both the L and R offset became much worse after a couple of days of use (75-140mv on both sides). Fortunately, several hours of searching the AK forum archives revealed that poor chassis grounds could cause excessive offset with this particular Yam rcvr. So, I once again, cleaned and carefully tightened every screw I could find on the chassis including the rear panel, face plate, and the bottom panel (which, imo, was the most important).
This simple procedure dropped the DC offset to a steady 20-23mv on both sides.
I'll also mention that the service manual contained the steps required to "check and adjust" the transformer voltage output while seemingly indicating that this could effect the DC offset. This was the only time that the S.M. mentioned anything about DC offset (the voltage was well within specs, so I left this adjustment alone).
HTH.
