#1
So I happen to own an old school jcm800, the 4210 (50w, 1x12 split-channel model). Date slip inside the amp shows that it's an 82'! (First year of dual channel 800's)

This amp has been out of commission for some time now. But I'm now debating between fixing it, or selling it as is. Basically, one day, the overdrive channel somehow stopped working, but the clean channel is still intact. I had a guy take a look at it (who happens to own a book with schematics for every pre-1990 Marshall amp), and he told me the circuitry that controls the signal path for the OD channel is fried, and that I needed to buy a small part to fix it.

Problem is, I don't know what the part is called, or how to find it. He wasn't able to find it either, and doesn't have the time to help me fix the amp.

I'm guessing a shop will charge out the @$$, and I'd end up spending $250+ on it, even if it's just a simple repair. It's money I won't really have for a while.

Another thing I've also considered is going with a more-high gain amp..unless it's possible to get a Bodom/In Flames/Dark Tranquility tone out of it.

I know own thing's for sure though...I sure miss hearing that OD channel cranked!

How much would the amp be worth as is? and are my repair cost estimates accurate for taking it to a shop?
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#2
I'm sure taking this thread into GB&C should be able to get you some answers. If you have a multimeter, it's possible to check the signal path yourself and find out what's wrong. It might be as simple as a blown cap, in which case it's not much work to replace it and save yourself an arseload of cash.
If you can find out what the problem is and then you take it to a tech, that should also save you a lot of money. Keep it and fix it IMO.
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#3
Research small part. Buy it. Get friend to install it. Play the crap out of it.
#4
Quote by FlightofIcarus
I'm guessing a shop will charge out the @$$, and I'd end up spending $250+ on it, even if it's just a simple repair. It's money I won't really have for a while.

I think its worth it getting it fixed, bring it to them anyway, you only assume they will charge you that (Well you mite assume right with those money making bastards ) But its worth a shot to get a estimate!
#5
I got the same problem with a vintage laney. '85 it was made 'Laney Pro Tube Head'

Cleans great, distortions fried. Its going to get repaired stat!

Just watch out for sneakin labour costs! Some shops charge you £30 from the second you leave the shop, even if its as easy as swappin one tiny part over.
#6
AN 82 JCM FIX IT MORON
dude seriously that amp is worth it's weight in gold (not actually but it's a sweet ****ing amp)... don't let some schmuck go and take that from you for cheap and let him fix it up KEEP IT... In Flames uses marshall i think...
If you want that tone though go with RANDALL amps... they are way heavier on the low end response
#7
Research it. Find out what you need. Look inside and see if you can find any visible damage.
#8
It could just be a bad input jack. I plugged into a JCM800 at Guitar Center and the jack seemed to cut out when i would wiggle it. Pissed me off. Check the input jacks out.
#9
Marshall themselves do spares. It's likely they have got the part, as they still make the 2210 as a reissue, and seeing as it's the dirty channel I imagine the pre-amp is the same so it should be the same part.

Only problem for you, if you're not in the UK is that Marshall is based just outside of Milton Keynes (30 miles from London or so). However, they can probably ship abroad, and it will be the best price for the part and it's the best place to go to. An alternative would be to find a broken jcm800 and salvage - this could end up being a hybrid monster, seeing as you want to play metal it might be a good monster...

There are contact details for their spares on the website, yes they are English so might not be quite so enthusiastic to help at first, but that's just our nature and they'll see to it for you.
#10
I'd keep the amp and try to fix it. It's hard to just let go of an old Marshall tube amp.
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#11
That's a great little amp and good enough to hang onto. Real Marshall tone that you can carry in one hand. Tell me there's ever gonna be a time in your life where that won't seem like a good idea.

Now the technical side of it. The channel switching circuits that Marshall first designed for the 2205 family were pretty buggy. The power supply for the switching circuit is often a problem. The main filter capacitor for that circuit should be replaced just to be sure. They fail regularly and can cause a weird warbling tone. Many times it's the transistor array IC that goes. I don't recall the number right off. But it may have been what your friend identified.

Channel bleed was a very common problem until they changed the circuit in 1987. A good tech can update your amp to that spec at the same time he repairs the fault in yours. Other typical problems are the solder joints and the footswitch jack.

I'll bet your amp gets fixed for something between $110 and $150 - getting it upgraded to 1987 specs could cost more depending on where you are. It's probably overdue for maintenance anyway. Get it completely gone over and cleaned while it's already in the shop.
#12
Quote by Xeragus
AN 82 JCM FIX IT MORON
dude seriously that amp is worth it's weight in gold (not actually but it's a sweet ****ing amp)... don't let some schmuck go and take that from you for cheap and let him fix it up KEEP IT... In Flames uses marshall i think...
If you want that tone though go with RANDALL amps... they are way heavier on the low end response


No.

In flames use peavey 5150.

Dark Tranquility use peavey 5150.

Bodom use a rackmount lee jackson preamp and a vht poweramp (alexi.)

Its not worth that much money, its just an amplifier. You might have to look hard to replace it, but you can always find one again.

Personally, I would fix it. The part may cost money, but fixing it is better than selling it IMO. You wont get nearly as much as you could for a working amplifier and then someone else will just go and get it fixed and have a perfectly great working amp when you're stuck with a little bit of cash (not enough to buy a decent high gain tube head) and depressed because you just sold your marshall.

My advice is to look around for marshall fans/pros and message boards and try to isolate the exact problem and then try to find a way to fix it. If you can't find the exact part I'm sure you can find something produced today that will be able to replace it with little to no modification.
#13
Go straight to marshall, seriously they can at least point the way. Plus I've met Jim Marshall, he seemed a jolly old fella.
#14
Well aside from fixing up the electronics, I'm pretty sure the tubes are due for replacing too. Both the pre-amp tubes and power tubes were replaced a little less than 2 years ago. It's seen mild-moderate use.

Which brings me to another question. The amp has 6550 power tubes in it now. Should I stick with those or switch to EL34's for the sound I want? The 6550's sounded awesome with a boost pedal in front of it, but without one, it had way too much low end. Could be my guitar too though.

PS: I should also mention, that when I select the OD channel, the light that indicates the channel is on still lights up, but no sound comes out of the speakers...Wouldn't that be something other than the power supply?
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Last edited by FlightofIcarus at Mar 1, 2007,
#15
Quote by FlightofIcarus
Well aside from fixing up the electronics, I'm pretty sure the tubes are due for replacing too. Both the pre-amp tubes and power tubes were replaced a little less than 2 years ago. It's seen mild-moderate use.

Which brings me to another question. The amp has 6550 power tubes in it now. Should I stick with those or switch to EL34's for the sound I want? The 6550's sounded awesome with a boost pedal in front of it, but without one, it had way too much low end. Could be my guitar too though.

PS: I should also mention, that when I select the OD channel, the light that indicates the channel is on still lights up, but no sound comes out of the speakers...Wouldn't that be something other than the power supply?


Yeah, its probably one of the relays or maybe even a preamp tube plaguing your amp. Those would be the first things I would check at least.

Tone-wise is all up to you. Personally, I'd prefer an amp with EL-34s right now because I have two that are tubed with 6L6.

If you like your amp that much its probably worth it to keep the bugger. Sentimental value and all that (plus jcm 800s kick alot of ass)
#16
Quote by FlightofIcarus
Well aside from fixing up the electronics, I'm pretty sure the tubes are due for replacing too. Both the pre-amp tubes and power tubes were replaced a little less than 2 years ago. It's seen mild-moderate use.

Which brings me to another question. The amp has 6550 power tubes in it now. Should I stick with those or switch to EL34's for the sound I want? The 6550's sounded awesome with a boost pedal in front of it, but without one, it had way too much low end. Could be my guitar too though.

PS: I should also mention, that when I select the OD channel, the light that indicates the channel is on still lights up, but no sound comes out of the speakers...Wouldn't that be something other than the power supply?


EL34's in a 6550 equipped JCM800 are not a drop in replacement. Theres some light modding to be done.

Namely, solder a 47k resistor parallel with the one already there by the bias pot, then you take take the feedback wire and solder it onto the 8 ohm speaker tap (the wire is purple).

Then rebias around 37-38k.
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#17
Let me try this again. There are no relays. There is a transistor array IC that does the switching. This switching circuit has its own supply. Every component of this switching circuit is subject to failure and never worked especially well in the first place. The Cap needs replaced, because if it isn't bad yet, it will be. The Transistor array is probably the main problem. Since work on this amp requires getting under the circuit board a good technician will take care of all of it at once.
#18
So it's official. I've decided to take it to a tech. I'll be dropping it off at a shop tommorow. Hopefully it all goes well!
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#19
Lets hope its not extortionate costs to fix it!
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#20
Good luck.
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#21
Ah, so I got it back yesterday, back to it's former glory. And the repair costs only came out to a bit over 65 bucks.

I almost slapped myself for considering getting rid of it that easily.
- Gibson Flying V 120 #1 (White)
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- Gibson SG Standard ('61 style)
- Jackson DK2M

- ENGL Fireball 60
- Avatar 4x12

- Many pedals, plus other stuff
#23
dude id kill for a JCM 800

get rid of it before i find u

nah just kidding

id fix it, a working condition one is worth more than a non working one anyway

edit: ooh even better. if i had a JCM800 id never sell, but possibly for a million dollars or more..
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#25
Yeah, what part of the od channel circuit was "fried" ??
Tone is all ...... well probably 75%, in your fingers.
The rest depends on your wallet's thickness !!

Keep the faith, baby!!
#26
Hey
Great you have it fixed! I have the same amp with EL34's in it. I will reccomend this to you. Mine was overheating, the tubes cook themselves off BAD, the danm thing overheats and shuts down after 20 minutes, I ended up making a custom piece of wood for the back with some fans on it, fix my problem right away, Prior to doing that fix I screwed a tubesocket solder joint up. Just a heads up for you Enjoy the amp, it screams- if you really really really really wants some major umph/balls out of it put a Emenince Red Ryder 200watter speaker into that or in an extension cab. That thing "wow" is all I can say, you can literally run that amp on spinaltap mode 11,11, 11,11 all the way

Enjoy!
#27
Quote by Got2MuchGear
Hey
Great you have it fixed! I have the same amp with EL34's in it. I will reccomend this to you. Mine was overheating, the tubes cook themselves off BAD, the danm thing overheats and shuts down after 20 minutes, I ended up making a custom piece of wood for the back with some fans on it, fix my problem right away, Prior to doing that fix I screwed a tubesocket solder joint up. Just a heads up for you Enjoy the amp, it screams- if you really really really really wants some major umph/balls out of it put a Emenince Red Ryder 200watter speaker into that or in an extension cab. That thing "wow" is all I can say, you can literally run that amp on spinaltap mode 11,11, 11,11 all the way

Enjoy!


What do you wire the fans to?

My laney glows and ive had to wire a old pc fan upto old mobile phone charge

Ghetto i know but it works!

Glad you got it fixed!
#28
Quote by Got2MuchGear
Hey
Great you have it fixed! I have the same amp with EL34's in it. I will reccomend this to you. Mine was overheating, the tubes cook themselves off BAD, the danm thing overheats and shuts down after 20 minutes, I ended up making a custom piece of wood for the back with some fans on it, fix my problem right away, Prior to doing that fix I screwed a tubesocket solder joint up. Just a heads up for you Enjoy the amp, it screams- if you really really really really wants some major umph/balls out of it put a Emenince Red Ryder 200watter speaker into that or in an extension cab. That thing "wow" is all I can say, you can literally run that amp on spinaltap mode 11,11, 11,11 all the way

Enjoy!


That generation of Marshall should not be heating up like that. If it's getting that hot, it's a symptom. Not that running a fan isn't nearly always a good thing. But you should look into getting it biased properly or otherwise repaired.
#30
Quote by Xeragus
AN 82 JCM FIX IT MORON
dude seriously that amp is worth it's weight in gold (not actually but it's a sweet ****ing amp)... don't let some schmuck go and take that from you for cheap and let him fix it up KEEP IT... In Flames uses marshall i think...
If you want that tone though go with RANDALL amps... they are way heavier on the low end response

Hardly worth its weight in gold. 80's 800 combos show up in pretty good condition all the time for around $800 on ebay. If you guys want one so bad then just get one...they're cheap and easy to obtain
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