hifi engine

Service manual for Kenwood RXD-25L or advice of tracking gain adjustment on the pickup servo PCB

Does anyone have a service manual to this device. CD player's skip function is not working, play works fine. I need to do some adjustment to tracking gain variable resistor on the pickup servo PCB.
There are four variable resistors on the PCB (VR1, VR2, VR3 and VR4). I guess these four are FG (focus gain), FB (focus bias or balance), TG - tracking gain and TB - Tracking balance. Problem is I don't know which one is which. Does anyone know for sure or does anyone have a service manual?