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Post subject: 94 Twin Amp reverb feedback with nothing inserted
Posted: Tue May 13, 2014 7:08 pm
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After soldering the new R25 pot into the board and putting it all back together, I get a high pitch feedback/ring with reverb set to >5. I have to zero the reverb to get the feedback to stop. This is with nothing inserted into the input and all volumes set to 1/off.

I replaced all the tubes in the amp so I know the tubes are good. I even put in the opld tubes, one by one, to see if one of the new tubes may be giving me trouble. I get the same problem now with the old tubes also.

This did not happen before I put the R25(second channel gain) pot in the amp. The pot works fine too. Everything is fine if I do not use the reverb.

I was wondering if there is some type of circuit that may have been disturbed or if there is a wire that is not shielded causing this.

I retouched up some solder joints too. Just so happens that the wires I also touched up were the reverb jack wires, but that made no difference.

Any thoughts would be greatly appreciated?

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Conley Shepherd
Joyful Noise Productions
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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 1:28 am
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IMO you move some wire when removing printed circuit to solder you pots ( is it a printed circuit made amp ? )

Any picture inside your amp will help to tell you which wires to look at .

In many Fender amps there is some grey flat wires which give some noise / feedback if not bend as they need .


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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 1:40 am
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http://forums.fender.com/viewtopic.php?f=13&t=93941

http://forums.fender.com/viewtopic.php?f=13&t=93813

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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 1:45 am
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I see you other post about humming , see a picture of your amp , not enough to help .

Better to open only one post with all your questions . Next time .

You have feedback AND hum ??


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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 5:18 am
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stratele52 wrote:
I see you other post about humming , see a picture of your amp , not enough to help .

Better to open only one post with all your questions . Next time .

You have feedback AND hum ??

Thanks for everyone's patience with me. If you would prefer all issues in one thread, I will do that and start no more threads.

I will take some pictures after I get the caps replaced. It is tore apart right now.

Originally when I got the amp, it had a hum, not very loud, but still there and it got louder when putting the gains up on ch1 and ch2.

The other issue was the R25, ch2 gain, scratchy pot.

The R25 is resolved and now I am working on the hum.

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Conley Shepherd
Joyful Noise Productions
(No, I am NOT an amp repair guy) ;)


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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 9:41 am
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I have replaced the caps and here are the pics of the amps innerds. There is still a light hum and still the reverb feedback. So back at square 2.

Image
Image
Image
Image
Image
Image

If there are particular shots you need, please let me know. I really do appreciate any help you can give.

and the higher resolution pics:

http://www.joyfulnoiseproductions.org/amp4.jpg
http://www.joyfulnoiseproductions.org/amp5.jpg
http://www.joyfulnoiseproductions.org/amp6.jpg

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Conley Shepherd
Joyful Noise Productions
(No, I am NOT an amp repair guy) ;)


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Post subject: Re: 94 Twin Amp reverb feedback with nothing inserted
Posted: Wed May 14, 2014 9:44 am
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and thes other higher def pix.
http://www.joyfulnoiseproductions.org/amp1.jpg
http://www.joyfulnoiseproductions.org/amp2.jpg
http://www.joyfulnoiseproductions.org/amp3.jpg

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Conley Shepherd
Joyful Noise Productions
(No, I am NOT an amp repair guy) ;)


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