HP 9865A Cassette Memory service manual?

Picked up a very dirty but nearly entirely functional HP 9810A recently, with 9865ACassette Memory drive. While I wait for parts to repair the 9810's mag card reader and printer to arrive, I've been working on cleaning up the9865A. It is almost working (and the few rubber parts in it seem to be good) -- however it will not move the tape forward. There are two solenoids that control the direction of the tape and one of them (for the forward direction) is not activating. It shouldn't betoo difficult to trace down the circuit and find the faulty part but before I dig too deep I thought I'd see if anyone has a service manual for this thing. I've looked in the usual places on the 'net and haven't found anything, aside from Tony's notes for the interface. Thanks as always, Josh