# Weird noise from vintage super reverb



## ampaholic (Sep 19, 2006)

Hi folks,
My '68 Super Reverb (AB763) is making a weird noise. This is going to be hard to describe but here goes!
The noise happens after plucking a single note. although it doesn't happen with every note on the fretboard I can't determine a pattern. Happens with high notes, low notes, etc. The volume doesn't have to be cranked but I do find that I have to pick quite aggressively in order to make the noise happen. The noise is best described as a whooshing sound although it is very short in duration and happens just a second (or less) after picking the note.
The obvious thing is tubes and I have tried replacing them all one at a time with no improvement.
Filter caps and bypass caps have been replaced with Sprague Atoms within the last 5 years.
I know this doesn't give you much but any advice on what this might be or how I might go about isolating the stage causing the problem?
Thanks!
Paul


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## nonreverb (Sep 19, 2006)

Original speakers in that puppy?



ampaholic said:


> Hi folks,
> My '68 Super Reverb (AB763) is making a weird noise. This is going to be hard to describe but here goes!
> The noise happens after plucking a single note. although it doesn't happen with every note on the fretboard I can't determine a pattern. Happens with high notes, low notes, etc. The volume doesn't have to be cranked but I do find that I have to pick quite aggressively in order to make the noise happen. The noise is best described as a whooshing sound although it is very short in duration and happens just a second (or less) after picking the note.
> The obvious thing is tubes and I have tried replacing them all one at a time with no improvement.
> ...


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## ampaholic (Sep 19, 2006)

nonreverb said:


> Original speakers in that puppy?


No, I actually have 4 Weber Classic series; 2 alnico and 2 ceramic. They sound great!


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## Gizmo (Aug 7, 2008)

Both channels?


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## ampaholic (Sep 19, 2006)

Gizmo said:


> Both channels?


Aah, now there's a good question. I haven't checked that. Stay tuned!


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## Tyler Savage (Nov 16, 2009)

I think it's hopeless and you should probably just give me the amp


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## ampaholic (Sep 19, 2006)

Tyler Savage said:


> I think it's hopeless and you should probably just give me the amp


Ha! I'll keep that in mind!


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## nonreverb (Sep 19, 2006)

Is the reverb on when it happens?


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## ampaholic (Sep 19, 2006)

nonreverb said:


> Is the reverb on when it happens?


Yes, although since you asked if it happens in the normal channel I haven't been able to get it to do it at all! So, fair to say that it is intermittent and doesn't seem to be related to how long the amp has been on. I can play it for an hour without any problem, then turn it off and back on and it starts.


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## keeperofthegood (Apr 30, 2008)

ampaholic said:


> Yes, although since you asked if it happens in the normal channel I haven't been able to get it to do it at all! So, fair to say that it is intermittent and doesn't seem to be related to how long the amp has been on. I can play it for an hour without any problem, then turn it off and back on and it starts.


Bad caps. Not the e-caps, the couplings.


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## nonreverb (Sep 19, 2006)

ampaholic said:


> Yes, although since you asked if it happens in the normal channel I haven't been able to get it to do it at all! So, fair to say that it is intermittent and doesn't seem to be related to how long the amp has been on. I can play it for an hour without any problem, then turn it off and back on and it starts.


Sorry, I meant to ask if it happens when plugged into the reverb channel. But since you state that it doesn't happen in the normal channel, I suspect that the problem may be in the reverb circuit.
Can you tell if the tank is original?


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## ampaholic (Sep 19, 2006)

keeperofthegood said:


> Bad caps. Not the e-caps, the couplings.


Hey thanks. Would checking them with a capacitance meter show anything?


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## ampaholic (Sep 19, 2006)

nonreverb said:


> I suspect that the problem may be in the reverb circuit.
> Can you tell if the tank is original?


I would be almost certain the tank is original. The amp came out of a church and i don't think had ever been touched. I guess that when the problem happens I could disconnect the pan and see if its still there?


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## keeperofthegood (Apr 30, 2008)

Well, the way I understand it is this. Capacitors can suffer an electrical version of vapor-lock. So, the odds are no; you may see it on a scope but not on a DMM. Would be best to get it recorded with no notes played, or use a pitch fork (if it is strong enough) on the pickup and get a clean tone to do it. Then you could trace with the scope for where the signal is being introduced.

Though reading over this again, having to drive the input hard to cause it, sounds like energy is punching through a cap. Maybe you can try pushing up the gain with a pedal and see if it becomes a constant issue?


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