Class 5 Tube Rattle Frustration !!

[happyhack]

Hello. New to the forum. Searched extensively for answers concerning the noise issue. I apologize if I've missed something. I'm beginning to think it's the infamous rattle. My initial thoughts were that it was a tube. It's not!!
I have a new Mark II, C5, three piece back, low wattage switch, version. Latest and greatest. The version that "cured" the rattle. (????)
Here's the issue:
After the amp has been on for a few minutes, I will develop a tube rattle at certain frequencies. It sounds very similar to a bad tube. It develops at any volume level above 2 on the dial. Certainly worse on the neck pickup. I would consider it above nuisance level. It's actually annoying. Owned several tube combos over the years, understand the dynamic between tubes/speaker/frequencies, etc.
So, having been down this road before, I figure we've got a bad tube. No big deal. I do the tap test at full volume. Nothing really noted. So, using the grip/pressure test on the tubes while playing a note that causes the rattle/harmonic or whatever the noise is, I isolate the EL84 power tube. Put pressure on it, and it stops. Cool. Problem solved. Order up a new JJ EL84 from Doug's Tubes.
Replace the EL84 (more on another issue later) plug in, and.... nothing has changed! Same exact rattle, at the same frequencies!
Now I'm concerned. I take the amp apart. Nothing lose. Everything as it should be compared to the diagrams from Marshall. In the process, I notice that the chassis has a rubber mounting "washer" enabling the chassis to push against the speaker.
That was my first "WTF?"
In addition, the rubber grommet on the EL84 tube retainer is "fused" to the tube. Literally. Make that my 2nd "WTF?
So, I took advantage of the situation, and removed the metal tube cage altogether. Tried again with the new tube. Nope, same "rattle".
New tube, old tube, with cage, without cage, with dampers, without dampers.
Took off the metal screen in the middle of the back. Nope.
Took off the bottom piece of wood. Nope.
But, if I put pressure on the EL84, either pinching side to side (squeezing), or upwards pressure (pushing), the offending noise stops.
I'm thinking of trying a couple Tube Dampers from Eurotubes. But what if that doesn't work?
I really like the amp. I want to try and cure it. I don't want to keep throwing time and money at it. HOPING to solve the problem.
I assume running it thru a separate cabinet would solve the problem.
But that's not why I bought it. I bought a combo. I bought a combo from a manufacturer who admitted to a problem, and convinced me that they had solved or fixed the problem.
Do I have the infamous rattle? Or something else?
Thanks in advance for any help or insight.

[happyhack]

To add: Les Paul P-90's. Have made pickup height adjustments. In addition, every EQ setting possible. Including no bass.
Also offends equally on low wattage setting.

[surfnorthwest]

Welcome to the Roadhouse. This rattle problem is usually attributed to the tubes themselves but it sounds like you have addressed that. It also sounds like you have done about everything reasonable to try to isolate the rattle. From here forward it really is going to be a trail and error or search and destroy thing where you just have to nail down where its coming from.

Based upon what you have tried and wrote I would start to look at the chassis and ensure it is not rattling up agianst the cabinets somewhere. Remove the chassis from the cabinet keeping the speaker plugged in and try that. If it doesn't rattle then it is the chassis. You will have to get some weather stripping and stick it to where the chassis meets the cabinet.

[ClassicRock88]

Any chance this could be the power tube socket itself? I have a 2010 (mk II) and when I have had it apart for retubing I have noticed that the sockets are soldered directly to the board, as with many modern Marshalls. These sockets don't look as robust as those on a VM or DSL. Could a loose power tube socket be the rattle source? Personally I would have a tech check that one because of the filter cap shock risk.

[DirtySteve]

Any chance this could be the power tube socket itself? I have a 2010 (mk II) and when I have had it apart for retubing I have noticed that the sockets are soldered directly to the board, as with many modern Marshalls. These sockets don't look as robust as those on a VM or DSL. Could a loose power tube socket be the rattle source? Personally I would have a tech check that one because of the filter cap shock risk.

That's what I thought at first and posted on the "other" forum, but I think Surf might be on to something too. I have the older version and without knowing how the tubes mount on the new ones I can't picture it.

[surfnorthwest]

To add to this, recently I picked up another used 425 cabinet and with certain frequencies it rattled (buzzed) also. Turned out that one of the side handles on the 4x12 did not have the screws tight. After I tighten them down rattle was gone.

I would pull the chassis and if it still rattle then its the speaker or something not tight in the cabinet. If it stops then take care in placing some dampening material at the points where the chassis is touching the cabinet.

Let us know how it goes.

[happyhack]

Thanks for the replies. I have not been able to locate a chasis issue. Did receive a tip on "the other forum" that it may be the tube socket itself. Unfortunately, that appears to be difficult to access when I had it apart. Someone else suggested that it may be a preamp tube, in spite of what my experiment with the power tube says...

Both suggestions involve more money and time, with no guarantee of solving the problem. A problem I shouldn't have to be trying to solve, I might add.
If its a fantom chassis rattle, I say bullshit Marshall. You failed. Your product is inherently flawed. You knew it, you supposedly fixed it, and I believed you.

And I bought it.

[aristotle]

This has been my general experience with combos regardless of Manufacturer. I'm on a never ending rattle chase with at least one amp at any given moment in time. The mean time between power tube rattle in my Fender Twinamp is about a week. Still haven't solved that. My 65Amps Monterrey had a rattle issue with clips on the preamp tubes and as soon as I solved that, the rectifier (5AR4) became a rattle trap. retubed the Mesa 5x50 about 6 months ago which solved it's problem (temporarily I'm sure.) Oddly the only combo that I have that hasn't had a rattle problem with is my 90's vintage JCM900 1x12. Gigging, it isn't so much of a problem since the rattles get lost in everything else going on. But I'm OCD enough that it really bugs me to have a rattle when I'm playing alone. And if you try to record with these things, it's hugely noticeable.

So, if I have a choice, it's heads all the way for me. I doubt that there is anything wrong with the new C5 design...this sort of stuff just seems to go with the combo territory. In any case, to debug this stuff, I usually don't even bother with the tube-tap method with the amp in the combo. It's too easy to confuse one's self. I usually pull the amp from the combo and put it across the room. Cable it to the cab's speaker with a long speaker cable. Plug in and play "G" on the low "E" string (tubes seem to really hate "G" for some reason.) That will say for sure if it's a rattle in the cab / speaker or not. If not (and it's usually "not"), time to pull tubes and see which is causing the problem. I usually have a few known good pre-amp and power amp tubes of various varieties floating around. It's never a straightforward process though. Good luck!

[6B4G]

The most obvious thing has not been stated here, are you sure that the new EL84 is a good tube? From your description it does sound like a tube that is causing the problem, just from the fact that you hold it and the problem stops. It is not impossible for the new tube to have a vibration fault the same as the tube that was originally fitted. I would try another different brand of EL84 if it were my amp just to rule this out, or try the tubes you have in another amp if you have a friend or local shop that has EL84 fitted amps.

The Class 5 is a great amp, I have a MK1 which Marshall modified to the three part back early on in the rattle history, mine has been perfect (except for hum, which is another story) since this mod, but it did take a while to find an EL84 that sounded good and did not have some sort of rattle issue. As stated, it is the nature of the beast with Combos, but once you find a good set, I have amps that have been running on the same tubes for 25 years.............!

Best of luck

[happyhack]

Traded for an Egnater. Problem solved.
Thanks for the replies.

[surfnorthwest]

Sorry it didn't work out for you, I can tell your frustration.