I cured rattle in my Class 5

[pablues]

My replacement Class 5 developed the rattle/resonance problem and was really bad on bottom E and an octave higher.The noise would cease if i placed my hand on the upper area of the back panel.Looking inside the amp, the four cables running from the transformer to the board touch the back panel just where the noise seemed centered.I re-routed two of the cables under the earth wire that connects to the chassis.This pulled all four cables away from the back panel.
Put it all back together and the back panel can be felt to vibrate on certain notes but the noise is a tiny tiny fraction of what it was and is not a problem when playing.
Thanks to ClubAndCountry for his comments in the inside pix thread for the idea of trying this

[DeanM]

well done man!!!

[kissfanps]

Sweet! Could be as simple as that!

[chess999]

interesting...mine rattles as well. I've been reading that some feel it's the thinner gauge metal used on the chassis. This doesn't entirely make sense to me though because why would amps "develop" this issue. I mean you would either have it or not right away all the time if the chassis was vibrating against the cab ..right? So is your amp cured now? I really don't want to send mine back for a long factory wait especially if it's an easy fix which you seem to have found. If there was an issue with the chassis wouldn't using some kind of glue or puddy help to dampen?

[pablues]

The problem with the two units I've had seems related to the back panel vibrating.It's a very small box and I guess the speaker drives the chassis/back panel.I had tried some extra thin foam between chassis and panel with no advantage.In my case the noise was caused by contact between the cables and back panel.Whether the sound came from that point or from vibrations transferred to something else via the cables I don't know.
As to the problem developing after a while maybe the back panel moves more freely after its been vibrated by the speaker for long enough?

I have just had the combo apart again and fitted a celestion vintage 10 speaker;still no problem with unwanted noise.

[rvin28]

Hi Pablues,
I'm glad that you have sorted out your class 5.

How much difference does the Vintage 10 make?

I have thought about revalving mine with Mullards (assuming that I can lay my hands on some (not literally!)). However, would the amp need rebiasing and if so how can this be undertaken as I have yet to see a schematic for the Class 5?

:rocker

[pablues]

The vintage 10 seems less bright with more mids more aggression more snarl

[chess999]

let's see

[slowpokerhino]

Hi Pablues,
I'm glad that you have sorted out your class 5.

How much difference does the Vintage 10 make?

I have thought about revalving mine with Mullards (assuming that I can lay my hands on some (not literally!)). However, would the amp need rebiasing and if so how can this be undertaken as I have yet to see a schematic for the Class 5?

:rocker

The Class 5 does not need to be biased.

[pablues]

screw the warranty. I'm not afraid of this thing. I've tackled worse issues. I just opened her up. Mine must be the first "fix" by Marshall cause its got the thin foam strip between the chassis and back panel. I'm gonna take your advice and wire tie those orange cables down. Upon first inspection they certainly looked as if they could have been touching the panel. Since I'm going thru the trouble I wonder if it would also make sense to throw some more hot glue on those components? Also perhaps making a special gasket to fit around the edges of the panel might help?. Will probably change the tubes for sure later but might they need to be stabilized more from the vibration than the way they are now? Any other suggestions to help improve vibration dampening without totally killing the tone of the cab?

Hot glue on anything that might vibrate against something else can only help.Don't forget the metal section inside the upper back panel needs metal to metal connection with the chassis at some point so it can act as a screen.

[ClubAndCountry]

It would be nice if it did turn out to be as simple as this! I have to say it was the first thing I saw in that pic of the insides - it actually looked like the wiring bundle stuck out further than where the back panel would be, and it was a definite candidate for the rattle. As such it's an assembly problem not a design problem, so no fault of SteveD's. This kind of thing can be a real nuisance in combos of all kinds, and wires are a more common cause than you might think.

If it was me, I would cut the original cable tie, and make a small circle or figure 8 from the wires, then put a new cable tie on at the crossing point - or possibly (being careful to note which goes where!) disconnect the wires from the PCB, tie a loose knot in them, and reconnect. You don't want them absolutely tight but you do want to make sure they can't touch anything else.

Does the amp sound good with the Vintage 10? I like this speaker a lot, but I'm well aware that it's very dark-sounding, and from what I heard with the stock Class 5 I thought it might be too much so. It also has a lot of bass and lower-mid response as well as being more efficient, so it should make the amp sound bigger and louder, but equally might make the rattle problem worse if it's something other than the cables causing it.

[chess999]

No sorry fellas it's not that simple. This thing is hopeless. The problem is in the chassis and cab construction period. You can wire tie and hot glue everything you want in there and it won't fix the issue. Again this is a major "back to the drawing board" problem for Marshall. Too bad cause the amp smokes great. Do yourself a favor and trust me on this, don't waste your time, return the amp to Marshall.

[pablues]

Well the amp got through a two hour session last night with no rattle problems so it seems this one at least was fixable.