/diy/ - Do It Yourself

I've got this Technics GX-670 receiver I'm trying to troubleshoot but I am an amateur with circuit components.

Problem is I'm using it's preamp for my turntable but the receiver cuts in and out intermittently accompanied by a "click" which I understand to be one of the relays. Shouldn't be over-heat since this sometimes happens from a fresh start with no prior use that day but I suppose there is could be some component triggering a false positive however -
Receiver still outputs sound when using the FM Tuner mode even when there's no sound for Phono and a good hard smack on the side often will induce the "click" and restore Phono sound. I checked the soldering underneath and on the preamp/relay board and seems OK to my amateur eye.

Could be a problem with the selector switch? Haven't messed with that. One of the large eletrolytic capacitors has a slightly raised surface on top but I haven't pulled them off to test.
Also I've verified the turntable works fine independently.