Tascam 112 pitch control problem

[technoplayer]

I recently acquired a pair of Tascam 112 cassette decks. They work well except the pitch control on both of them exhibits the same problem.
When i enable the pitch control button, the capstan motors spool up to high speed, and the pitch knob has no effect. They both do the same thing, so i was wondering if this was a common issue and what the fix is.

ANy ideas? If not, does any one have a ciopy of the manual and schematics so I can try to troubleshoot this?

Thanks