# Vintage Fender Volume Pot Issue



## GuitarsCanada (Dec 30, 2005)

Might be a volume pot or maybe something else. This is on the old super reverb. The normal channel sounds like the speakers are going to blow right out of it with the slightest turn on the volume knob. Channel two on the reverb/tremolo side works perfectly in all respects.

Am I looking at a volume pot issue or something more sinister?


----------



## Cups (Jan 5, 2010)

Usually a dirty pot doesn't sound that dramatic but if the other channel is working well it's more then likely the volume pot. With the amp off try turning the trouble pot back and forth a dozen times. Sometimes that's enough to dislodge the dirt from the pot.


----------



## jb welder (Sep 14, 2010)

If exercising the pot like Cups suggested makes any difference, then it is likely a bad pot. Or you can try a control cleaner (such as deoxit) and see if you get any change. If there is any change but it won't clean up, you will need to replace it.
If there is no change then you should check for DC voltage on any of the pot terminals using a multimeter. Any DC voltage on the pot will mean there is another problem elsewhere.
One more thing to try would be swapping V1 and V2. Sometimes a bad tube will put DC on the pot and cause bad noises when the pot is turned.
If after swapping V1 and V2 the problem goes to the other channel, you know the tube is causing the problem.


----------



## GuitarsCanada (Dec 30, 2005)

I will perform these test and changes and see what happens


----------



## mhammer (Nov 30, 2007)

Is this a recent change in an amp you have used without problem until now? If o, then it is more than likely a dirt issue.

If it is something in an amp you acquired or were asked to fix, then the chances are also reasonable that someone replaced a log taper volume pot with a linear taper pot. Use of linear taper volume pots is an old "trick" by budget amp manfacturers to create the impression that "if it was this loud on 2, just imagine what it would be on 10!".

If it IS dirt, however, it is possible to take the pot out, pry the tabs up that hold the back cover on the pot, and clean the resistive strip with a Q-tip. Spraying with contact cleaner is also a viable strategy, but is most effective when you have easy access, and know you can fully spray the crap out of the pot.


----------



## GuitarsCanada (Dec 30, 2005)

mhammer said:


> Is this a recent change in an amp you have used without problem until now? If o, then it is more than likely a dirt issue.
> 
> If it is something in an amp you acquired or were asked to fix, then the chances are also reasonable that someone replaced a log taper volume pot with a linear taper pot. Use of linear taper volume pots is an old "trick" by budget amp manfacturers to create the impression that "if it was this loud on 2, just imagine what it would be on 10!".
> 
> If it IS dirt, however, it is possible to take the pot out, pry the tabs up that hold the back cover on the pot, and clean the resistive strip with a Q-tip. Spraying with contact cleaner is also a viable strategy, but is most effective when you have easy access, and know you can fully spray the crap out of the pot.


Problem is I NEVER use the normal channel to plug in, always the trem channel. So the other day I decided to plug into the normal channel, which I keep the volume knob turned off on, I discovered the issue. So no telling how long it may have been like that. I have owned the amp for years.


----------



## mhammer (Nov 30, 2007)

Which more firmly suggests there may be some sort of physical obstruction, maybe dust ball, inside the pot.


----------



## GuitarsCanada (Dec 30, 2005)

mhammer said:


> Which more firmly suggests there may be some sort of physical obstruction, maybe dust ball, inside the pot.


 At around 50 years old, that would be very plausible


----------



## Wild Bill (May 3, 2006)

GuitarsCanada said:


> At around 50 years old, that would be very plausible


Hell, after 60 years I've probably got a few dustballs rolling around in my innards!

Wild Bill/Busen Amps


----------



## mhammer (Nov 30, 2007)

As dusty as you and I may be, though, Bill, the puzzler here is that for the amp to sound like it's on "11", there would need to be what amounts to a short between the input lug and wiper of the volume pot. And between you and me, I can't imagine any way that dust alone could do that.

But you know what could? The bright switch. Normally, it provides a 120pf cap to straddle the input and wiper lugs of the volume pot so that highs are preserved when the volume is set low. If the bright switch was shorting, however, rather than only allowing signal to pass through the cap, then it would be like there was zero ohms between the input lug and wiper.

So, I'm going to suggest moving the bright switch around, and maybe cleaning THAT out, to see if it makes a difference.


----------



## epis (Feb 25, 2012)

Hi Mark, I'm not trying to be a smart ass, but it's hard to believe that bright cap got shot, and it would affect just upper side of the pot.
I think there is just a problem with loose rivet at ground connection of the pot. At zero setting of the pot, viper touches the rivet, all is OK,but when it comes to the carbon trace there is no more ground connection and it acts like at 11.
So GuitarsCanada,just use the pliers and squeeze the rivets on wafer board carefully to make a proper contact. Cheers, Damir

P.S.

It could be also already broken wafer bord, in that case, just replace the pot.


----------



## loudtubeamps (Feb 2, 2012)

epis said:


> Hi Mark, I'm not trying to be a smart ass, but it's hard to believe that bright cap got shot, and it would affect just upper side of the pot.
> I think there is just a problem with loose rivet at ground connection of the pot. At zero setting of the pot, viper touches the rivet, all is OK,but when it comes to the carbon trace there is no more ground connection and it acts like at 11.
> So GuitarsCanada,just use the pliers and squeeze the rivets on wafer board carefully to make a proper contact. Cheers, Damir
> 
> ...


Agreed........ 
a bad ground/lug connection would be my guess as well.


----------



## GTmaker (Apr 24, 2006)

Wild Bill said:


> Hell, after 60 years I've probably got a few dustballs rolling around in my innards!
> 
> Wild Bill/Busen Amps


Ive allways heard that a good bottle of Scotch will remove the dustballs.
If it doesnt work, its allways fun trying.


----------

