Picked up a bone stock 1982 JCM 800 2204 today...clip inside

[RedPlated]

This came up local on Craigslist. Completely stock, untouched 1982 JCM 800 2204. 6550 version. Drove about 50 miles today and picked it up from a super nice guy who’s had it in storage for the last 5 years.

I have an 83’ 2204 that I modded myself and I think it sounds really good. That amp didn’t sound the best stock. This 82’ sounds so much better. These amps are just inconsistent...

I took the 82’ home, scrubbed the tolex, fixed some tears and scrapes and then went through the chassis. I put a pair of GE 6550 in it. It had some crusty Svetlanas in there. It had 8th gen Chinese preamp tubes. Not my favorite in these circuits, but good in some others. I ended up with a CP Mullard short plate in V1, a Tungsram in V2 and a Sovtek LPS in the PI.

I wanted to leave this amp completely untouched. However, it did have some flubby bass at full gain. I had discussed this with Dave Friedman the other day and he pointed out that the “hot shield” input method Marshall used on these kills treble and makes for loose bass. It runs from the high input jack to a 68k grid resistor then into a shielded cable to the grid on v1, with a shield to the plate. I replaced this with shielded coax from high input directly to the grid on v1, with a 33k resistor on the grid. I have the same setup on my 83’. This is relatively non-invasive and easily reversible.

What a difference the input made. Loose bass gone, more highs. Sounds so good. This is a great stock Marshall. For anyone else with a stock 800, I’d highly advise changing the input and remove the hot shield. It kills the tone.

I made a quick clip at very low volume. Running into my 72 Marshall 4x12 and wet dry wet into a TC Gmajor2 for some delay. Didn’t touch the amp, just worked the volume knob and pickups. Guitar is a Charvel Nitro Aged San Dimas. BKP Holy Diver bridge and Dimarzio Transition neck.

 

[ultimatemetalguitartones]

Congrats! Nice playing! I suppose a boost will take it to the metal territory/!

 

[Buckeyedog]

Sounds great! Nice find.

 

[RedB4Black]

Nice score! Sounds great!

 

[SpiderWars]

Nice find! Always nice to get a good one. And that Transition sounds really good.

 

[Racerxrated]

Nice! Congrats. That's my fav year of any 800..check the plate voltage, I'd bet its at 500v or more. I've probably had 4 82s and they all sounded killer. I have an 83 2203 that also puts out over 500v; just a super aggressive killer Marshall tone esp with a boost. My 83 also has a quartet of GE 6550s.

 

[RedPlated]

Got some questions on the hot shield input mod. So I decided I’d post some info on how to do it.

Here’s how the factory input runs from the high input jack to v1 grid input. The red line shows how it runs from jack, to PCB, through the trace to the 68k grid stopper, to other side of board and out to the brown shielded wire. The wire enters the grid of the tube and the shield wire under the jacket of that wire runs into the plate next to the grid. This puts high voltage (B+) on the shield, reducing noise. It only shields the part of the cable from the backside of the PCB to the v1 tube, a small portion.

Remove this wire (red line drawn for reference), it can be green, pink, white, they used all kinds. It’s the bottom right corner terminal when looking from this angle. Desolder from the terminal and from the PCB and pull it out.

Do the same thing on the other side of the board with the brown wire that runs to v1 the same way you removed the green one. You’ll have to lift the board to desolder them. If you don’t care about originality, you can just cut both or either wire where they enter the board and save lifting the board. You can leave the 68k resistor between these two points installed on the PCB. No need to remove it.

On the other side of the brown wire, which has a gray sleeve, remove it from
V1 at both points, where it enters the grid (red line) and where the shield enters the plate (red arrow).

Now we need to make the new input with RG-174 coax cable. Here’s what it will look like when you strip the ends. We will call the side on the right side 1 and the side on the left side 2...

Side 1

Side 2

Side one is going to go to the high input jack where you removed the factory wire. The inner portion will go to the same terminal as you removed the stock wire. The ground braid wil go go the terminal opposite of that terminal, closest to the chassis, which is ground. In the following diagram, inner portion goes to “hole 2” and ground braid goes to “to buss wire” terminal.

On the opposite side of the coax, solder a 33k resistor directly to the inner portion. Fold the ground braid back against the sleeve. Shrink wrap the whole assembly. Make sure the ground braid doesn’t touch the inner wire.

Now after side one has already been soldered to the high input jack, run the cable under the PCB and angle it towards the v1 grid where you removed the stock shielded wire. You only are going to make one connection, to the grid only. The plate will NOT be used anymore. That was only used as a “shield” which we have now created by using a shielded ground on our coax.

Simply insert the 33k resistor into the grid terminal on the v1 tube and you are done. You’ll have tighter bass and more highs. Made a huge difference on my amp. I assume others will vary. But the hot shield isn’t doing you any favors, that’s for sure.

This is what it will look like when done:

 

[splawner]

Very cool of you to take the time to do this! Will be giving it a try for sure.

 

[RedPlated]

Here’s a boosted clip. JHS bonsai on JHS setting into a Schaffer Replica Storm. Les Paul with Duncan Alternative 8 pickup.

 

[splawner]

Here’s a boosted clip. JHS bonsai on JHS setting into a Schaffer Replica Storm. Les Paul with Duncan Alternative 8 pickup.

Sounds great!!!

 

[Bad.Seed]

Nice score and great playing man. Your amp wall setup is so clean, it gives me envy. Nothing like a good 800!

 

[stanz]

 

[Kapo_Polenton]

Maybe that's why my homebrew 2204 seems "tighter" than my 82? Going to open my 82 and see if it has this or if it was done differently.. I noticed for me at volume I back the preamp off to 8 on my 82' because it flubs out a bit too much for my liking. Also boost mine with the JHS Bonsai or Lil Brute Drive. I love that czech ODR setting but the Keely and JHS mod on the dial are also on another level. Insane.

What does the Schaeffer give you? Just a bit more push? like a clean boost for the Bonsai?

 

[fek]

Also boost mine with the JHS Bonsai or Lil Brute Drive. I love that czech ODR setting but the Keely and JHS mod on the dial are also on another level. Insane.

The ODR, Keeley, and JHS settings on the Bonsai are my go to's for sure. ODR for dark bottom heavy amps. The JHS mode is easily my favorite so far.

 

[Kapo_Polenton]

I almost feel guilty putting the JHS mode on... it is almost like "IF" I go here and I live here.. there is NO coming back. Am I ready for this??! So I hang out on the ODR lol. TS-9 sounds really good too though. OD-1 is fantastic for old thrash.

 

[RedPlated]

Maybe that's why my homebrew 2204 seems "tighter" than my 82? Going to open my 82 and see if it has this or if it was done differently.. I noticed for me at volume I back the preamp off to 8 on my 82' because it flubs out a bit too much for my liking. Also boost mine with the JHS Bonsai or Lil Brute Drive. I love that czech ODR setting but the Keely and JHS mod on the dial are also on another level. Insane.

What does the Schaeffer give you? Just a bit more push? like a clean boost for the Bonsai?

Bonsai on it own is a little too bright and cutting. The Schaffer adds some low mid and bass. Fills it out nicely. They just happen to be the two OD pedals on my board.

 

[Kapo_Polenton]

Interesting, I am all about cut and mids so maybe that's why I dig the Bonsai. I find it perfect for my needs. I checked my 800 and it is wired the way yours was, that might explain why things get out of control when the preamp is cranked and the master goes past 4.. thanks for posting that.

 

[RedPlated]

Interesting, I am all about cut and mids so maybe that's why I dig the Bonsai. I find it perfect for my needs. I checked my 800 and it is wired the way yours was, that might explain why things get out of control when the preamp is cranked and the master goes past 4.. thanks for posting that.

You’ll notice a lot less flubby bass by getting rid of the hot shield. Especially between 8-10 on the gain.

 

[halebox]

nice!