Collins 75S-1 Receiver S Meter Issue

[W2TRH]

Hello all, i have Collins 75S-1 Receiver that works well, all tubes check great, however when the RF gain control is turned up the s meter needle just goes all the way to the left and does not move,any idea on what could be wrong, thanks kindly for your time,
Steve
W2TRH

[W2JBL]

Is the meter pegged at left stop? Have you tried the S-meter adjust pot? I have a 75S1 and 75S3 and both of them had bad meter adjust pots. Try adjusting the meter (up off the peg) to zero unless you already have.