new 65 DRRI reverb issues

[tim]

Hey all,

I have had two brand new '65 DRRI's on my bench in the last month or so, both with the same issue, reverb feeds back when control is turned up over 4-5. I spent about 2 hours on the first one trying to figure out the source of the feedback. The feedback would stop (more or less) if I pressed down on the tank. I finally wrapped the tank in bubble pack, stuck it back in the bag and no more feedback. This one I have on my bench now, I did the same thing to and it fixed the problem as well.

Both these DRRI's had Ruby tanks in them. I was told that these are "rebranded" Accutronic tanks but they look totally different.

I contacted Fender on the first one and they said they weren't aware of any issues with these tanks. Are there any known issues with these tanks that we all know about but Fender doesn't, or isn't admitting to?

[nickb]

Dunno, but I had a very similar problem yesterday in a Princeton 65 with an Accutronics reverb. I had some 1/8in thick spongy rubber sheet. I wrapped it in that to solve the problem.

[Randall]

Me thinks like with almost everything else these days, the new tanks are not what they used to be. I also think they don't sound the same.

[Enzo]

Are you an authorized fender shop? If these are brand new, why beat your head against a wall, they have warranties. Let the nearest fender shop handle it.


meanwhile reverb feedback as a problem has been around as long as there have been reverb pans. We should have multiple threads about it here.

Here is a basic checklist.
1. pans are never to be screwed down tight. If they are exposed, they should be put in a bag, but if left out, the screws should only be tight enough to keep the thing from sliding around. The bag should have one or two screws near the ends to keep it stable.

2. Inside, make sure the inner spring assembly has not hopped up onto the guide posts, and that all four corner springs are intact. And all the long springs are intact.

3. Cut a cardboard bottom to cover the open side of the pan and tape it on. Then into the bag.

4. The long wide flat top surface can resonate. get some peel and stick weather stripping foam, and glue a line of it down the length of the centerline. That will damp off any resonance. This is the stuff you might run along a garage door to keep out drafts. Maybe 3/4" wide and 3/8" thick.

5. Sometimes position matters, moving the pan an inch or two can be enough to avoid a standing wave in the cab.

6. Sometimes just turning the pan upside down in the bag works.

7. Sometimes padding under the bag helps.

[tim]

Hi Enzo,

I am a certified Fender tech (gold) and do work in my own shop part time for several stores, one of them is a Fender ASC. I had done all those things you suggested except the weather strip on the top of the tank. I will have to try that the next time I see something like this. The bubble pack trick seemed to work on both so I left well enough alone. It was some sort of mechanical feedback happening.

In regards to Fender warranty...I'm a low volume shop so I sometimes have time to actually get into the wherefore and why of some of these problems. In this case I did so I decided to figure out what was actually causing the problem. I figured that it was something about the mechanics of the tank and ordering a new one would probably net me the same results.

Anyway, as always, thanks for the suggestions.

[Enzo]

OK, if you are authorized to do warranty work, then file the claim and get paid for it. I was concerned you were having to charge someone for something that should be free. it was not about your ability at all.

Pressing on the top of the pan making it stop leads me to think the weather strip just might work for you here. But if other means covered it, that's fine too. REsults are what matters.

[tim]

OK, if you are authorized to do warranty work, then file the claim and get paid for it. I was concerned you were having to charge someone for something that should be free. it was not about your ability at all.

Pressing on the top of the pan making it stop leads me to think the weather strip just might work for you here. But if other means covered it, that's fine too. REsults are what matters.

Haha! No problems on questioning my abilities Enzo...I certainly didn't take it that way but there are times I certainly do question them myself

I fill out the paperwork, the store pays me and then Fender reimburses them...win/win. I certainly didn't charge Fender two hours for the first repair (it would've been rejected out of hand).

Thanks again for your input.

[Chuck H]

I've read (but fact check if you can find enough info) that one of the (many) reasons Accutronics isn't Accutronics anymore is that they couldn't make the pans the way they use to and were getting too many warranty claims. The material that they made the damping gaskets for the spring drives from became unavailable, permanently. This info was from a respected member here.

Now, I can't say if that specific material is a real lynch pin in the design of spring drivers, but I can say that I've never had more trouble with microphonics in reverb systems than I do with new tanks of any brand. It's not uncommon for me to buy two or even four tanks before I have one that both works acceptably and sounds good. Since I'm a small builder that increases the averaged cost of the reverb pan to about $60!!!

Please excuse the following rant...

I've seen plenty of factory amps with reverbs operating well enough with the standard tank in bag arrangement or even with the tank screwed (loosely) to the chassis sitting on the supplied rubber feet with no bag. Yet I can't buy a replacement tank that doesn't howl in the top or bottom end when installed OEM. I get the feeling that all these cheap, production amps on the market are getting the premium part (because a complaint from a company that buys five thousand tanks a year goes further than "some guy with a problem") and what's available from vendors is second rate $h!t. Similar to what's been happening with tubes. But this is just one guys experience (mine) with the matter so I'm not making any definitive claims about it.

I've seen some boutique and small time builders go to the trouble of building a sort of iso chamber into their cabinets for the reverb tanks! "I" have had to experiment a lot to stabilize new tanks with the standard bag mounting. As Enzo says, the tank needs to be in a bag. The bag must be loosely screwed to the cabinet. Even bunched a little to elevate it from sitting flush to the cabinet bottom. And IMHE extra damping is usually necessary around the tank, in the bag. If bubble wrap alone worked for you that's great. I've had projects where that wasn't enough. In fact I've had projects where I needed to actually frequency tune the reverb circuit to avoid problematic frequencies and still cover the pan with something like a sliced up yoga mat to stop the feedback.

And then there's still the specifics of tank placement (even once a tank is cased in yoga mat). One spot may be non microphonic, but not ideal for induced hum!!! Placement for induced hum use to be the only thing I had to deal with. But now I'm fighting two problems that require different answers within one parameter!?!

I'm so tired of what has become the standard "modern reverb tank drill" that I'm seriously considering attempting to talk customers into digital systems for custom builds in the future.

I guess my point is... Yes, it's a problem. And IME a modern tank problem.