restoring my jcm 800



just bought a 89 jcm800 4212 combo.
its in horrid condition, everything works electronically (apart from 2 pots which are buggy).

i have pics of the chassis, but i dont know how to post them.
these are the things i want to do.

re-grill cloth
re tube (i want to put in the tubes that zakk wylde uses) 6550?.
i also want to see if i can get a replacement front panel, were the knobs are. i doubt i can get one but mine is all scratced up.

any comments or tips on these projects?

thanks all!

John Phillips

Re-grilling is relatively easy, but a pain to get really 'right' looking.

Re-tolexing is a total pain, best left to an expert, and almost impossible to get right-looking unless you really know what you're doing. You'll also need to remove and refit all the corners and handles.

Marshall do stock both materials though, and rivets for the hardware (you won't be able to re-use them).

A new front panel - no chance. You'd need to get it from Marshall, and it's highly unlikely they have any stock left. You could however make a reasonable job with some Letraset of the right size, and some clear varnish. But to do it nicely, you'll need to clean the panel up well first, and get it off the amp - not as easy as you may think since the power and standby switches are fitted through it too.

I'm not totally sure it's worth the cost and effort to be honest - it's really not a simple job to get that amp looking sharp again unfortunately...

To fit 6550s you have to change three resistors - one in the bias supply, and the two bias feed ones, and (I think) move the feedback tap on the impedance selector. Not a huge job. Alternatively, you could fit 6CA7s (US EL34 equivalent) which will give you a sort-of similar tone change without having to do anything other than adjust the bias with the trimmer. They're by no means the same, but the differences will be less noticeable at low volumes, where you're mostly hearing the preamp (IMO).


Actually, if you have to recover one, these type of cab are not too bad. You just roll it all the way around w/ the seam on the bottom, cut into the corners and glue the sides down, trim it and put the corner pieces on. The corner pieces cover all the bad stuff that shows up. I would not attemp an early Marshall (there are experts for that), but I did do a JCM800 and it was easy and looked perfect.


hey john,

ive never heard of letraset,what is it?
also when i mean scratched up, the gold plate looks nice but the writing is all worn and blotchy. just from old age and giging i suppose.

Lonely Raven

Isn't that like a $700 amp (USD)?

I really don't think it's worth all the effort since they are
rather plentiful.

I would take it to a tech and have him change it over to 6550,
get it totally looked over, and enjoy the mojo of years of use!

Unless you are doing the work yourself, you are looking at
some serious expense for all you want to do!

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