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In the past, as well as now, while going thru the inventory of Fender Twin Reverbs, I've had so much trouble with the stupid plastic open-top T/SN input jacks...particularly on the Normal Channel (for reasons unknown). Why this part became a 'standard' in their better combo amps is beyond me. What so often happens in time with these jacks is you loose ground continuity. Ground is made by a rectangular 'hoop' routed up and around the 3/8"-32 threaded bushing part pressed into the plastic body, and pressed into the grooved channels around this ground bushing. Oxidation eventually sets in, the press-fit loosens and you suddenly have loud barking from the channel if your cord's phone plug is pulled to one side or another. And, the Normal contact doesn't always make good contact, so you have hum that comes and goes when you disconnect while the volume control is up. These are the parts I"m talking about:
I've even installed brand new jacks like these, fresh out of Fender's spare parts packages, and you STILL have the same problems over in the Normal Channel. And, of course, a couple de-solderings of the jacks on that input PCB assembly and you've now gotta repair the PCB, as the tiny annular ring solder terminals designed on the board by the novice PCB layout person who don't know squat about serviceable solder pads have lifted off the PCB. Those input boards in general need to be re-designed, just from a service stand point! Fat chance of that happening.
I finally went in and retro-fitted some proper Switchcraft L12A open-frame T/SN phone jacks, and wired them in, scrapping these plastic wonders. There is enough space below to do it.
Those open frame jacks that we've been using for decades just can't be beat. Granted, not PCB mounted, so you have more fumble factor, particularly if you used the thin ITL washer between the chassis and the jack as I did, but all the jack problems are gone. No more scary noises when the cord is tugged on, nor do the cords pull out if you move out to far away from the amp (debatable attribute).
I've even installed brand new jacks like these, fresh out of Fender's spare parts packages, and you STILL have the same problems over in the Normal Channel. And, of course, a couple de-solderings of the jacks on that input PCB assembly and you've now gotta repair the PCB, as the tiny annular ring solder terminals designed on the board by the novice PCB layout person who don't know squat about serviceable solder pads have lifted off the PCB. Those input boards in general need to be re-designed, just from a service stand point! Fat chance of that happening.
I finally went in and retro-fitted some proper Switchcraft L12A open-frame T/SN phone jacks, and wired them in, scrapping these plastic wonders. There is enough space below to do it.
Those open frame jacks that we've been using for decades just can't be beat. Granted, not PCB mounted, so you have more fumble factor, particularly if you used the thin ITL washer between the chassis and the jack as I did, but all the jack problems are gone. No more scary noises when the cord is tugged on, nor do the cords pull out if you move out to far away from the amp (debatable attribute).
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