INSTEK GSP 810 how to adjust tracking generator frequency

[Txtom]

I bought a used INSTEK GSP810 which seems to work quite well exept for a problem with the tracking generator.
 The problem is that the tracking generator is sweeping too wide a frequency and so doesn't track the spectrum analyzer properly . It starts on the right frequency but sweeps too far out by about 15%. My guess is that there is a calibration pot inside or a hidden calibration menu item but I can't figure it out. Can anyone help with information or a service manual.  There is a pot labeled frequency on the back of the cabinet but it doesn't seem to do anything (maybe that's the one but broken).

[ohmedarick]

Hi:
Where you able to get the service manual GSP-810. Thank you

Ricardo