# Fender Concert reverb is squealing violently!!!



## vds5000 (Apr 14, 2008)

I reinstalled the chassis and reverb tank into my cabinet tonight and was greeted with a very loud high-pitched squeal coming out of my speaker. 

Disconnecting the reverb cables gets rid of the squeal. I checked inside the reverb tank and everything seems to be in order. I also double checked the connections, and all seems good, except for the violent squealing when the amp is turned on. When I took the reverb out of the bag and connected it to the amp, oddly enough, there was no squealing. 

I'm sure this is something simple, but the problem is that I don't know what the issue is.

Does anyone have any suggestions short of taking it to a tech?


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## greco (Jul 15, 2007)

vds5000 said:


> When I took the reverb out of the bag and connected it to the amp, oddly enough, there was no squealing.


Did the reverb work when it was out of the bag?

I can't offer any suggestions...but it just might be helpful for others who have experienced this type of problem to know the answer to the above question.

Good Luck with solving this.

Please let us know what caused the squealing.

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> Did the reverb work when it was out of the bag?
> 
> I can't offer any suggestions...but it just might be helpful for others who have experienced this type of problem to know the answer to the above question.
> 
> ...


Oddly enough, the reverb did work when it was out of the bag. Additionally, all was good before I took everything out to retolex the amp a few weeks back.


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## greco (Jul 15, 2007)

vds5000 said:


> Oddly enough, *the reverb did work when it was out of the bag.* Additionally, all was good before I took everything out to retolex the amp a few weeks back.


Now my curiosity is killin' me.

When it is out of the bag, can you recreate the squealing by moving the wires (especially near the RCA connectors...assuming they are RCA connectors)...just wondering if there is a possibility of one of the wires or grounds making and breaking connection or shorting to each other.

BTW... All this is just guessing on my part as I have virtually no knowledge of/experience with reverb circuits.

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> Now my curiosity is killin' me.
> 
> When it is out of the bag, can you recreate the squealing by moving the wires (especially near the RCA connectors...assuming they are RCA connectors)...just wondering if there is a possibility of one of the wires or grounds making and breaking connection or shorting to each other.
> 
> ...


I haven't tried that. Admittedly, I've got all the testicular fortitude in the world when it comes to ripping tolex off a perfectly good amplifier. But when it comes to the electronic aspects of an amplifier - I'm a chicken. Too scared of breaking something and too scared of getting zapped.

I've been doing some reading online over the past few minutes and one compelling scenario is that the tank is secured too tightly to the cabinet. I don't think that's the case here - the reverb bag I'm using now is larger than the original one being used. ARGH - this is so frustrating!!!


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## greco (Jul 15, 2007)

I don't know if it makes a difference, but the amp tech that worked on my SF Princeton Reverb put a piece of corrugated cardboard (full size of the bag) between the cab and the bag. I asked him about that, and he said "That is the old way of doing it"...I'm still not sure why. Might be worth a try...for the sake of a piece of cardboard.

Please don't mess with the wires if it feels uncomfortable/unsafe to you (even with a chopstick) ....it was likely not a very wise suggestion on my part. Sorry.

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> I don't know if it makes a difference, but the amp tech that worked on my SF Princeton Reverb put a piece of corrugated cardboard (full size of the bag) between the cab and the bag. I asked him about that, and he said "That is the old way of doing it"...I'm still not sure why. Might be worth a try...for the sake of a piece of cardboard.
> 
> Please don't mess with the wires if it feels uncomfortable/unsafe to you (even with a chopstick) ....it was likely not a very wise suggestion on my part. Sorry.
> 
> ...


Actually, the tank has a piece of corrugated cardboard already under it. Plus, I lined the entire bottom of the amp with thin foam to help reduce vibrations to the reverb tank.

No worries about the suggestion - I wouldn't do anything that I wasn't comfortable doing.


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## Ripper (Jul 1, 2006)

just out of curiousity, did you have the reverb cables plugged into the same jacks outside of the cab as when you had it inside? did you try reversing the cables in the jacks?


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## Ripper (Jul 1, 2006)

One other thing, are the fine wire inside the reverb tank that connect to the jacks okay? If was one broke/loose it might be making contact when you have it out and then loosens when back in. Just thinking out loud here.


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## Adicted to Tubes (Mar 5, 2006)

Try this: get rhe squeal going and then hold the reverb driver tube(third tube from the right looking at the rear)with your fingers.You won't get burned or shocked.Then do the same with the recovery tube.If the squeal stops,you have a microphoic tube.Jostling the chassis around can loosen up the internal workings of a tube.When you had it out for retolexing it may have been bumped a bit.It may not take much.

A bad cable,even if it's shorted,won't cause a squeal.The reverb simply won't work.


www.claramps.com


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## nonreverb (Sep 19, 2006)

Try replacing the cables to see if that makes a difference.


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## vds5000 (Apr 14, 2008)

Ripper said:


> just out of curiousity, did you have the reverb cables plugged into the same jacks outside of the cab as when you had it inside? did you try reversing the cables in the jacks?


I did not remove the cables from the tank, but did remove them from the chassis when I removed everything from the cab. When I put it back together, I tried switching the cables. When I have the inputs/outputs mismatched, there is no reverb at all. When I have them plugged in correctly, there is squealing.




Ripper said:


> One other thing, are the fine wire inside the reverb tank that connect to the jacks okay? If was one broke/loose it might be making contact when you have it out and then loosens when back in. Just thinking out loud here.


I visually checked the fine wires inside - they seemed ok. However, I do understand that a visual check is not really as thorough as what I need. I believe there is a way to check for continuity using a multimeter (which I coincidently purchased on Sunday). If anyone out there knows how, please feel free to chime in - I would be greatly appreciated.




Adicted to Tubes said:


> Try this: get rhe squeal going and then hold the reverb driver tube(third tube from the right looking at the rear)with your fingers.You won't get burned or shocked.Then do the same with the recovery tube.If the squeal stops,you have a microphoic tube.Jostling the chassis around can loosen up the internal workings of a tube.When you had it out for retolexing it may have been bumped a bit.It may not take much.
> 
> www.claramps.com


Ok, there seem to be 7 preamp tubes - a group of 4 near the centre, and a group of 3 on the right (looking at the amp from the back). So the reverb tube driver is the 3rd from the far right (looking at the amp from the back). Which tube is the 'recovery' tube? I'm hoping it's just a tube. This amp has cost me much more than orginally anticipated.

One more thing - one thing I did not check was to see if adjusting the reverb level affects the volume of the squealing. I'll check it out tonight and report back.

Also, thanks all for the advice - I'll try all the suggestions tonight after work.


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## greco (Jul 15, 2007)

vds5000 said:


> I believe there is a way to check for continuity using a multimeter (which I coincidently purchased on Sunday). If anyone out there knows how, please feel free to chime in - I would be greatly appreciated.


You now have some very experienced and knowledgeable forum members helping you. I'm happy to be learning from them...however,too bad that it is at your frustration/"expense"

I'm assuming here that your meter is digital. Many meters have a continuity setting that will buzz when you touch the probes to each other. Somtimes this is denoted on the meter selector as a little speaker symbol. Check your user's manual.....If not, set the meter to the lowest DC resistance range and touch the probes...look at the screen and that symbol will be what you want to see for continuity. Make sure the probes are clean (which should be the case if your meter is new) and that you make good solid contact with the probes to the wires/connectors being teated.

Hope this helps. 

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> You now have some very experienced and knowledgeable forum members helping you. I'm happy to be learning from them...however,too bad that it is at your frustration/"expense"
> 
> I'm assuming here that your meter is digital. Many meters have a continuity setting that will buzz when you touch the probes to each other. Somtimes this is denoted on the meter selector as a little speaker symbol. Check your user's manual.....If not, set the meter to the lowest DC resistance range and touch the probes...look at the screen and that symbol will be what you want to see for continuity. Make sure the probes are clean (which should be the case if your meter is new) and that you make good solid contact with the probes to the wires/connectors being teated.
> 
> ...


The frustration will disappear quite quickly if I can resolve the issue and learn a thing or two.

The meter I bought is just a cheap analog one from Crappy Tire. I think I'll be returning it and looking for a better one.


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## greco (Jul 15, 2007)

vds5000 said:


> The meter I bought is just a cheap analog one from Crappy Tire. I think I'll be returning it and looking for a better one.


You can still do continuity with the analog meter....using the DC resistance method.

However, getting a digital one (with a buzzer for continuity) is worth the few extra $ .....IMHO

Cheers

Dave


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## Adicted to Tubes (Mar 5, 2006)

Locate the reverb transformer on the chassis looking at the rear of the amp.The driver tube is immediately to the right of the transformer and the recovery tube is to the left.
Before you get all bent out of shape about cables and tank,confirm that it's not a microphonic tube.
You can get a set of RCA cables at a dollar store to test for bad cables.
Squealing to me sends me straight to the tubes first and then lead dress or an oscillation.Again,tube related.The driver tube is a 12AT7 and the recovery tube is a 12AX7.You should have a spare set of tubes on hand if you are going to own tube amps.They ease diagnostic troubles if you can substitute tubes before assuming all sorts of other things.

www.claramps.com


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## vds5000 (Apr 14, 2008)

Adicted to Tubes said:


> Locate the reverb transformer on the chassis looking at the rear of the amp.The driver tube is immediately to the right of the transformer and the recovery tube is to the left.
> Before you get all bent out of shape about cables and tank,confirm that it's not a microphonic tube.
> You can get a set of RCA cables at a dollar store to test for bad cables.
> Squealing to me sends me straight to the tubes first and then lead dress or an oscillation.Again,tube related.The driver tube is a 12AT7 and the recovery tube is a 12AX7.You should have a spare set of tubes on hand if you are going to own tube amps.They ease diagnostic troubles if you can substitute tubes before assuming all sorts of other things.
> ...


Ok, I'll check for the reverb transformer when I get home. I do have plenty of RCA cables just lying around at home, so I can use those to check things out. I also have some spare new 12AX7's that I can use to test as well.

A quick and naive question regarding your diagnostic test involving my checking the driver and recovery tubes - all the preamp tubes have metal covers - do I need to remove the covers from the 2 reverb tubes to perform the test?


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## Rugburn (Jan 14, 2009)

vds5000 said:


> A quick and naive question regarding your diagnostic test involving my checking the driver and recovery tubes - all the preamp tubes have metal covers - do I need to remove the covers from the 2 reverb tubes to perform the test?


Yes, just give them a turn/twist and they pop right off. Also when you replace the covers make sure they're on nice and snug or you might get some rattling when you fire it back up. You wouldn't be the first guy to say "Well, it sounds good now except for this buzzing sound". I would also suggest you get a 12AT7 to troubleshoot this problem properly. They're cheap and easy enough to find.

Shawn :smile:


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## greco (Jul 15, 2007)

Any luck repairing the reverb yet?

If yes.....what was the cause of the problem?

Cheers

Dave


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## vds5000 (Apr 14, 2008)

Rugburn said:


> Yes, just give them a turn/twist and they pop right off. Also when you replace the covers make sure they're on nice and snug or you might get some rattling when you fire it back up. You wouldn't be the first guy to say "Well, it sounds good now except for this buzzing sound". I would also suggest you get a 12AT7 to troubleshoot this problem properly. They're cheap and easy enough to find.
> 
> Shawn :smile:


Thanks Shawn - and you're right, a little twist and they popped right out.

So, I went home and before I turned on the amp, I noticed that the RCA plug on the cable that connected to the 'Reverb In' jack on the chassis was a little loose fitting. So I took my pliers and bent it slightly to make it fit more snug. Guess what? When I turned on the amp, the squealing was gone. I did however take the covers off the 2 tubes associated with the reverb (to the left and right of the reverb transformer). I gently tapped/jiggled the 2 tubes and no squealing! So, hopefully the issue is resolved.

Thanks for all the help folks - it was much appreciated.

Now, I'm off to play the amp a bit.

Charles


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## greco (Jul 15, 2007)

:rockon2: :smile: :wave:
...and did you get a new (exchanged) digital multimeter also ? I forgot to ask this in my last post.

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> :rockon2: :smile: :wave:
> ...and did you get a new (exchanged) digital multimeter also ? I forgot to ask this in my last post.
> 
> Cheers
> ...


I haven't had a chance to return it yet - probably will on the weekend.


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## Ripper (Jul 1, 2006)

Glad to hear you got it fixed. It struck me that it had to be wiring as it worked at different times, usually with a tube, it's bad, its bad and moving the reverb tank around wouldn't have changed the problem. Congrats on the repair.


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## greco (Jul 15, 2007)

Ripper said:


> Glad to hear you got it fixed. It struck me that it had to be wiring as it worked at different times, usually with a tube, it's bad, its bad and moving the reverb tank around wouldn't have changed the problem. Congrats on the repair.


Even though I will likely never come close to being very skilled at electronics, I'm feeling better all the time that *some* of my troubleshooting analysis/thought sequences are improving. I'm learning so much from folks in this forum.

Many thanks (to all) for sharing your knowledge and explaining your reasoning.

Cheers

Dave


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## vds5000 (Apr 14, 2008)

greco said:


> Even though I will likely never come close to being very skilled at electronics, I'm feeling better all the time that *some* of my troubleshooting analysis/thought sequences are improving. I'm learning so much from folks in this forum.
> 
> Many thanks (to all) for sharing your knowledge and explaining your reasoning.
> 
> ...


+1

This is a decent forum. There are some people who let emotion get the better of them occasionally, but I for one do appreciate the info shared with some of the knowledgable folks on here.


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