Princeton Reverb cabinet rattle

Marc Morfei

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I am having a devil of time chasing down the rattle in my Custom68 PR. I have searched every post on this site and everywhere, and I know this is a very, very common problem that is very hard to isolate. I had one of these amps a few years ago and it was dead silent. I got rid of that one because it was too bass-heavy. But I picked up another one recently from a guy on CL because it has an Emi Legend 1028 speaker in it, and I have to say it sounds fantastic. The 1028 definitely tightens things up a lot. It sounds pretty well balanced to me now, nice and creamy and I love the early breakup.

Anyway, the dreaded rattle is very inconsistent. It comes and goes. Only get it above 5 on the dial, triggered by low frequencies. From what I have read, there seems to be no single cause for this. Could be many things. I took it to a tech who took it apart and verified there is nothing wrong with the amp or tubes electronically. It's a vibration issue. If you take out the baffle the sound disappears.

I have tried all the easy and obvious things. Tightening all the screws did not help at all. I put weather stripping all around the baffle and that did help quite a bit. Actually, at first it did not help, because I cranked the screws down tightly. Then I thought to loosen the baffle screws, and it got a lot better. But I am still getting a very faint fizz sometimes. I put it through a looper and pushed and prodded every single place I can find. No luck. If I had to guess, it's coming from somewhere around the tube sockets. If you grasp a tube firmly, the fizz reduces just a bit.

As much as I like the amp, I have no desire to throw hundreds of dollars and dozens of hours at guessing randomly at the problem. I'll just live with it, or sell it, or trade it in somewhere. There is only one low-cost/effort idea I have left. So this is a very long post to get to a very specific question: has anyone had any luck with tube dampers? The heavy-duty ones from Eurotubes seem to get good reviews. Maybe those would help dampen the vibration?
 

Peegoo

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It's probably the top of the baffle. It floats.

When the PRRI first came out, I got one and it had an annoying buzz. I narrrowed it down to the floating baffle.

So I removed the baffle, removed the speaker, and unstapled the fabric across the top. I used a router to create a channel 1/4" wide x 1/8" deep all the way across the back of the baffle and epoxied in a maple stick 1/4" thick x 1" wide. That really stiffened up the baffle and solved the problem.

Note that there is a bias-adjust pot that has an access hole (looks like a 1/4" jack) near the front of the chassis. If you install a stiffener like this, you may block access to the adjustment...so pay attention to how far the stiffener reaches under the front of the chassis...or use a rasp/file to make a small notch in the stiffener to allow a screwdriver in there.
 

Boreas

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My understanding is that it is usually a baffle issue. Changing humidity may help with the inconsistency. I believe that changing the baffle was the usual fix.
 

corliss1

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I also had a brand new one with a baffle issue a few months ago. Customer just got it, and we quickly determined the issue was in the baffle itself. We ended up doing a Fender warranty exchange on that one as they wouldn't/couldn't send a new baffle as it was a limited run with non-standard grill cloth. I realize that isn't an option for you since you aren't the original owner, but that was my odd PRRI baffle story.
 

DennisM

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I had a rattle in my 65 PRRI Bordeaux. It was the metal tube protector attached to the back panel. I tightened it and it still rattled. I removed it completely and the rattle was gone.
 

Jowes_84

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Patience, time and a good plan usually enable you to find the culprit. Go from one possible source to the other. It’s annoying, but not impossible. Above suggestions are a good start. Good luck.
Tube dampeners … imho NO. Locate the rattle (may be more than one source) and reduce it by eliminating the source.
 

Willie Johnson

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I had a rattle in my 65 PRRI Bordeaux. It was the metal tube protector attached to the back panel. I tightened it and it still rattled. I removed it completely and the rattle was gone.
I had the same issue with my Super Champ X2; removed the tube detention center and it went away. I've been meaning to do it to my PRRI on principle alone. So stupid.
 

Marc Morfei

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I had a rattle in my 65 PRRI Bordeaux. It was the metal tube protector attached to the back panel. I tightened it and it still rattled. I removed it completely and the rattle was gone.
Yeah, removing that was one of the many things I tried. Not the culprit in this case, unfortunately. The weather stripping around the baffle almost solved it, but not quite. I could cut a new plywood baffle and give that a shot. I just don't have time for any more projects right now....
 

schmee

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I read about a solution last year that is seldom talked about. I'll see if I can find it..... Wasn't the baffle.

How thick is the baffle on these? Baffles are pretty simple devices. A Bassman 4 x 10 only had a 5/16" baffle and it wasn't a big issue. A DR only has 4 screws holding it's baffle and some even had JBL's in them with no rattle.
I assume the PRRI has standoff strips to hold the grill cloth off the baffle?

I remember now; it was the tube sockets that cured the problem in that thread last year... Power tube sockets I think. The socket itself is loose in the metal retainer around the socket. he could wiggle it around. New sockets and it went away.
 
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Willie Johnson

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I remember seeing someone on here bolt a piece of aluminum angle metal onto the top of the baffle for these as a stiffener, to good result.

I've wondered myself about the Mojotone baffles and whether they drop in without fitment issues--I've got a 12" speaker I'd like to try in my PRRI, but don't want to fuss with cutting a new baffle and redoing the speaker cloth if I don't like it, or want to switch back and forth.
 

EsquireBoy

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It's probably the top of the baffle. It floats.

When the PRRI first came out, I got one and it had an annoying buzz. I narrrowed it down to the floating baffle.

So I removed the baffle, removed the speaker, and unstapled the fabric across the top. I used a router to create a channel 1/4" wide x 1/8" deep all the way across the back of the baffle and epoxied in a maple stick 1/4" thick x 1" wide. That really stiffened up the baffle and solved the problem.

Note that there is a bias-adjust pot that has an access hole (looks like a 1/4" jack) near the front of the chassis. If you install a stiffener like this, you may block access to the adjustment...so pay attention to how far the stiffener reaches under the front of the chassis...or use a rasp/file to make a small notch in the stiffener to allow a screwdriver in there.
I had the same issue with my PPRI and it was the top of the baffle too. I came up with the same solution but less fancy: I screwed a steel bar into the top of the baffle and the rattle was gone.
 

schmee

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I read about a solution last year that is seldom talked about. I'll see if I can find it..... Wasn't the baffle.

How thick is the baffle on these? Baffles are pretty simple devices. A Bassman 4 x 10 only had a 5/16" baffle and it wasn't a big issue. A DR only has 4 screws holding it's baffle and some even had JBL's in them with no rattle.
I assume the PRRI has standoff strips to hold the grill cloth off the baffle?

I remember now; it was the tube sockets that cured the problem in that thread last year... Power tube sockets I think. The socket itself is loose in the metal retainer around the socket. he could wiggle it around. New sockets and it went away.
https://www.gretsch-talk.com/threads/weird-rattle-noise-in-68-custom-princeton-solved.208654/
 

Marc Morfei

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I had the same issue with my PPRI and it was the top of the baffle too. I came up with the same solution but less fancy: I screwed a steel bar into the top of the baffle and the rattle was gone.
That's interesting. There is a good amount of space between the top of the baffle and the chassis. Many solutions I read about involved somehow wedging some material into that space. But those didn't work for me. The weather stripping around the sides where the baffle comes into contact with the cabinet did help, as I said earlier. I was hesitant to go with the router idea, just because that involves tools i don't have. But attaching a rigid piece to the exposed top of the baffle might be pretty easy. I guess the idea is to stiffen it? And keep it from vibrating as much? Weird. Lots of amps have floating baffles with no issue, in fact I have come to think that is the preferred way to do it. Anyway, sounds like nobody likes the tube damper idea.
 

Marc Morfei

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schmee

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Thanks, yeah I did come across that post in my searches. Something to keep in mind. I didn't want to start with that because I'm not sure I have the knowledge or skill to do that work myself, and I already paid once to take it to a tech. I can solder, but that's about the extent of my knowledge of electronics. But it's good to know that is a possible cause.
I would think silicone sealant applied nicely with a plastic syringe between the metal and socket would solve any tube socket rattle. Silicone is good for something like 400 degrees F.
 




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