[Drake] TR7-A VFO Problem?

[n1udi at att.net]

I would like to run this by the Drake buffs on the reflector. My trusty TR7-A has been acting strange the past few weeks. The problem is that when I switch the rig to the 7 Mc (that's old school terminology ) and above position. The VFO will not lock on to frequency. If it does lock then it might just start free running incrementing up or if it does lock on frequency when I key the mic it will take off running again. If I'm on 40m I can turn off the rig off and it may lock on or it may not. It will not lock on to 20M or any thing above. 

I checked the voltages on the power supply board in side the rig. They are up to specs. Cleaned the band switch contacts with trichioroethane what little bit I still have left. Any ideas or your thoughts before I take the cover off and dig into this again?  The strange thing is that the rig is rock steady below 7Mc. Thanks for any input in advanced.

73's Rock