MIL-Q
Member
Do you have 60hz hum from your preamp that seems to come and go and changes in amplitude when you press the selector switches making you think DeoxIT may be needed yet didn't fix it?
Try tightening the the screws that mount the rear of the pcb board to the chassis via the aluminum L-brackets.
Better yet, first place an inner-tooth lock-washer between the bracket and the chassis and then tighten the screws down tight! The lock-washer teeth dig into both the chassis and the L-bracket insuring a good gnd.
Give the screws on the pc side a snug down as well.
Background story: The pcb gets chassis gnd through the two brackets at each rear corner of the pcb. You should notice that the factory originally scraped off the chassis finish at both locations to insure a ground but over time the metals oxidize (and the screws loosen) and your chassis ground degrades.
Also, obviously, you may have bad electrolytic filter caps in the power supply. But try the screw fix first. Then replace the caps anyway. Even if they're not yet bad they will likely fail sooner or later and you already have the cover off....
Try tightening the the screws that mount the rear of the pcb board to the chassis via the aluminum L-brackets.
Better yet, first place an inner-tooth lock-washer between the bracket and the chassis and then tighten the screws down tight! The lock-washer teeth dig into both the chassis and the L-bracket insuring a good gnd.
Give the screws on the pc side a snug down as well.
Background story: The pcb gets chassis gnd through the two brackets at each rear corner of the pcb. You should notice that the factory originally scraped off the chassis finish at both locations to insure a ground but over time the metals oxidize (and the screws loosen) and your chassis ground degrades.
Also, obviously, you may have bad electrolytic filter caps in the power supply. But try the screw fix first. Then replace the caps anyway. Even if they're not yet bad they will likely fail sooner or later and you already have the cover off....