| Author |
Topic: reverb feed back loop in fender twin |
Jon Graboff
From:
Santa Fe, New Mexico
|
Posted 28 Aug 2002 10:23 am |
|
| Has anyone encountered this. I'm using an original '65 Fender Twin reverb and I'm getting weird feed back in the reverb circuitry. I'm not sure if this is of any informational use, but the feedback sounds like a steady tone around "A" below middle "C". As you turn up the reverb knob, the tone gets louder and goes away entirely if you turn the reverb down all the way. I've swapped out preamp tubes with no difference. Otherwise the amp works and sounds great. Comments? [This message was edited by Jon Graboff on 28 August 2002 at 11:25 AM.] |
|
|
|
Jay Ganz
From:
Out Behind The Barn
|
Posted 28 Aug 2002 11:13 am
|
|
I've got one of the old 65's as well.
I haven't had a problem like that, but
did you try swapping spring units or
connecting cables? It's the easiest
thing to try next. If it's none of
those, then possibly a dried out bypass
capacitor on the 12AT7 (next to the little
reverb transformer) or the 12AX7 on the
other side of it. Those two tubes are for
the reverb. |
|
|
|
Donny Hinson
From:
Glen Burnie, Md. U.S.A.
|
Posted 28 Aug 2002 8:43 pm
|
|
| Sounds like the bypass caps are shot. These small electrolytics (which prevent "feedback loops") will cause all sorts of whistling, screeching, and "motorboating" noises when they go bad. |
|
|
|
Ricky Davis
From:
Bertram, Texas USA
|
Posted 28 Aug 2002 11:15 pm
|
|
Change the reverb tubes. These are the tubes on each side of the transitor unit towards the right/middle looking at the back of the amp.
Ricky |
|
|
|
J Fletcher
From:
London,Ont,Canada
|
Posted 29 Aug 2002 4:55 am
|
|
| Could be the springs feeding back. They are acoustically insulated within their bag in the bottom of the amp, but sometimes the tank needs to be loosened up within the bag so it's more isolated from the speakers...Jerry |
|
|
|
Ken Fox
From:
Nashville GA USA
|
Posted 29 Aug 2002 11:52 am
|
|
| Seen and fixed this more than once. Unplug the reverb cables and try it again. If it howls, replace the 25mfd at 25WVDC at the reverb recovery tube, V4. Like Donny said, this is a common problem. I have recently helped two guys on the Fender Forum with the same problem and fixed a Twin recenlty that had the same problem. |
|
|
|
