Tek 577 white/green wire of Max peak Volts (S120x) switch location in schematics

[rodd]

Dear all,
I am trying to fix a 577 and can't complete the Vertical gain adjustment procedure.
The DMM connected between pin 4 of P129 and this white/green wire of S120 reads 8v when the OFFSET MULT pot is at minimum, so I need to troubleshoot this part of the circuit.
This voltage is generated in Step Amplifier (Diag 3) and it is ok @ TP360 so the problem is between TP360 and pin 4 of P129, which is located at the vertical amplifier input (dig 6).
The white/green wire seems to be the ground/return wire for this signal, but it would make troubleshooting easier if I could locate this point on the schematics.
Any idea of where it is?
Thanks,
Roger