My Marshall JCM800 cab rattles like uber F**K!! How do fix?

WiresDreamDisasters

My Marshall JCM800 rattles like almighty fuck. If I do a palm mute, it wants to breakdance across the floor it rattles and vibrates so bad. I think it's partially the handles, and partially the backboard. What can I do about it?

It's a cheap nasty cab that I use for practice. Would still like to improve it if I can though.

octatonic

Try taking the back off it and see if removing mass changes the resonant frequency of the cab.

ICBM

It the back board warped? They can do that, especially if they get slightly damp, and then they rattle against the end of the centre soundpost. The solution is to drill a hole through the back and screw it tightly to the post.

If the handles are rattling and they're screwed on, take them off, run a line of silicone sealant (bathroom type is fine!) round the edge of the hole and then put them back with it wet. If they're rivetted on it's much more of a pain... 

ESBlonde

I have seen these sort of cabs were the centre post has fallen down inside so that the rear baffle is left to vibrate. Once you've taken the back off and put it back on you will think about getting an electric drill driver ;-) just make sure the bit is quality so you don't chew up the screw heads. Always tighten the last bit up by hand.

Getting your head down beside it while it's 'vibrating' might give you a clue as to what is at least the symptom.

Bygone_Tones

Always check your speakers. If the spider supports have come unglued this will cause a horrible rattling noise when you play. See step 1 here: https://www.bygonetones.com/how-to-test-a-celestion-greenback-speaker.html

WiresDreamDisasters

I'm probably gonna go into the practice room tomorrow with some tools and have a go. I'm pretty sure it's the backboard and handles because it goes away when I apply pressure to them both.

ICBM

If you're going to screw the backboard to the post, check that the post is centred first, or at least close! You don't want to drill a hole in the back and find you've missed it .

Some people put a small piece of foam or something on the end of the post to damp any vibration, but this actually pushes the board out and makes it warp even more.

Stevepage

A dab of silicone around areas such as handles, the back panel and even the board that the speakers screw onto.