Twin Reverb Help

Travis

Active member
Hi!!

I´m trying to fix my twin reverb, It´s have background noise even if the guitar and cable are disconnected and all volumes down.

I tried to replace all preamp and power amp tubes. Also to disconnect or move the reverb tank and also to plug it in different places.


It´s a background hum noise but it´s loud.

Some ideas? Thank you everyone
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If you've already ruled out the tubes, the next thing I would look for is bad connections somewhere. A few questions for investigation:
  • Are you still getting audio through over the noise?
  • Does moving any of the knobs affect the noise in any way?
  • Did the noise change at all when you changed tubes?
  • Have you opened up the chassis to look at the board?
  • How old is the amp? Is it modern PCB construction or older eyelet board?
  • Have you tried plugging it into different outlets to see if there's a bad ground somewhere in the house?
I'm not a Fender authorized technician, but I've poked around a couple Fender amps and I'll help if I can.
 
Which model Twin is it? Is it the '65 RI? If so have a look at Psionic Audio's Youtube videos on how to fix Fender RI BF amps. There is a good chance that he has covered your issue!



I haven't seen these particular videos but there are issues which are common across the range so the Deluxe Reverb videos can help.
 
One thing that would cause hum is the power supply filter caps bring shot. Reduced filtering would cause hum. Dried up or blown up caps, same results. On the old Fender amps the caps sit in the 'doghouse'. It's about 4X6 inches or so and it's mounted on the outside of the chassis. Lots of voltage in there!! The series choke in the B+ will help reduce hum however.
 
Glad that fixed it for you! Built five guitar tube amps from '07 to '10 if you count a complete re-build of the second one. Haven't done much with tube builds since then.
 
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