# NAD - Marshall JCM 800 2204 CSA



## SG-Rocker (Dec 30, 2007)

THE SEARCH IS OVER !!



As some may know, I have been contemplating on whether to build or buy a Marshall 2204.

Recently, a forum member just sold an amazingly mint JMP era 2204. I desperately tried to liquidate surplus gear to raise the funds but was too late which was a real bummer. As it turns out, everything happens for a reason because no sooner did I finally sell off my no longer needed gear, a local (20km away) ad popped up on Kijiji for a 2204 and 412 cab. I talked them down to $1200 and made the pickup !







Complete with the often missing back panel.







CSA compliant toggle switches







Lucky number sevens ! The R means that this was made in '83







Which is verified on the build tag..


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## SG-Rocker (Dec 30, 2007)

The couple I bought this from didn't really know much about it other than it was all original right down to the tubes. They also said that it had not been used in at least 20 years and spent most of its life in storage. And boy did it show...














Ewwwww!!
















Has anyone here ever heard of POLAMP tubes ?














Now for the power tubes …. Uh Oh !


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## SG-Rocker (Dec 30, 2007)

The glass on that blown tube is sunk in on both sides...

(unbranded Tesla?)

























So I took the amp out to the garage and gave it a good blowing out and a rubdown with solvents to clean out the gunk and this is what came back...

(note the CSA mandated fuse board)














The third fuse in from the left was blown... no doubt a result of the power tube that self destructed.














Luckily I had a set of brand new Mullard reissues I had previously ordered from The Tube Store for my YCV50 but never got around to installing. I will need to venture out for a replacement fuse tomorrow.



The next thing to do was to scrub the cabinet of 33 years of nasty funk...


















More to come ….


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## Moosehead (Jan 6, 2011)

Nice grab. Did you get the cab too? If so check and see if you got the g12 65, its THE speaker for these amps. That's quite the deal if you got both pieces. 
I have the combo version and this amp is 100% ro k n roll, which I'm sure you already know. 

Enjoy.


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## SG-Rocker (Dec 30, 2007)

The cab was a JCM900 badged 1960A cab. The speakers inside were G12T-75s dated from 1990.
I'm cleaning it up this week.

I have a newer 1960A cab loaded with G12-65 reissues and lemme tell ya... AC/DC Powerage for days.
I can nail the intro chords to Down Payment Blues :-D


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## Moosehead (Jan 6, 2011)

Wise in the ways of the g12 65 magic you are lol. I'm not sure if my speaker is a reissue or not but compared to my 70s greenbacks they have a bit more high middle range and volume! My treble knobs never moves, stays maybe a hair over 4 (10-11 oclock). The dialing in is mostly between the middle and presence.

G 12 75s were pretty much the standard in those cabs I think. Given the age I assumed you got a jcm 800 cab. Love the sound of this amp through my 4x12, I only use 2 speakers though. 
Still pushes enough air to lean back into the sound.HNG^%$


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## guitarman2 (Aug 25, 2006)

Nice grab. I'm thinking I want a JCM 800. I've been seeing a few on Kijiji.


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## SG-Rocker (Dec 30, 2007)

I got it running last night... very impressed.
I m going to boldly say that I have found my sonic nirvana.



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## BSTheTech (Sep 30, 2015)

Stellar purchase. The "non-working" state got you a great deal. On the plus side it's due for new tubes and a tune-up anyway so win-win. Well done!

*Unless you are an amp tech I'd get the servicing done before you install your new tubes and fuse and flick the switch. That tube may have blown for a reason.


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## SG-Rocker (Dec 30, 2007)

BSTheTech said:


> Stellar purchase. The "non-working" state got you a great deal. On the plus side it's due for new tubes and a tune-up anyway so win-win. Well done!
> 
> *Unless you are an amp tech I'd get the servicing done before you install your new tubes and fuse and flick the switch. That tube may have blown for a reason.


I have no qualms dealing with the servicing component and am well equipped to do nearly everything.
My only curiosity is whether or not to replace the electrolytics? 
The look healthy, show no signs of distress and there is no excessive hum to be heard. In fact it's just as quiet as my YCV50 !
I do plan on installing a set of 1 ohm resistors on the power tubes to simplify future biasing.


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## al3d (Oct 3, 2007)

OHH...nice score man...congrats


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## Budda (May 29, 2007)

Congrats! I have a late '83 2203 CSA!


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## jb welder (Sep 14, 2010)

I've seen those Polamp tubes, not very often though. The EL34's with nipples on top are I believe EI brand from Yugo?
If you got it running, I guess it was just a tube fault?
Had there been a bias issue at that power tube socket, the replacement you put in would probably red-plate.


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## BSTheTech (Sep 30, 2015)

SG-Rocker said:


> I have no qualms dealing with the servicing component and am well equipped to do nearly everything.
> My only curiosity is whether or not to replace the electrolytics?
> The look healthy, show no signs of distress and there is no excessive hum to be heard. In fact it's just as quiet as my YCV50 !
> I do plan on installing a set of 1 ohm resistors on the power tubes to simplify future biasing.


 My understanding is if they aren't oozing brown goo you are ok. Let'er rip tater chip!


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## ezcomes (Jul 28, 2008)

thats awesome! and a killer deal! congrats!


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## SG-Rocker (Dec 30, 2007)

I just picked up the only mod this amp will ever see...








These will make bias measurement and adjustments much easier and at $2 it's a lot cheaper than a bias probe!

And to the technically inclined, yes they are metal film :-D

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## BSTheTech (Sep 30, 2015)

I have the same amp (4010). Interested to see how that works.


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## SG-Rocker (Dec 30, 2007)

Ok mods done. I must say that the power tube wiring is pretty shite from the factory. The melted wire insulation is original and not my doing. I can foresee a future project of replacing the power tube sockets and cleaning up the wire dress.

Enough of that, on with the pictures....

Completed mod... I'm pointing one of the resistors with the test lead.









Let's check that plate voltage - yup, that would tingle a bit haha !









Let's see what the bias was originally set to.... holy hotness!









65% dissipation should be around 33-35 mA so I went with 35.

Oh and I found a crappy solder here at the screen resistor...









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## Lemmy Hangslong (May 11, 2006)

SAWEET. That uis a great find and great story behind it. Congrats on a stellar NAD!


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## xbolt (Jan 1, 2008)

Very cool...congrats!

I found a similar Canadian JCM800 2203 a few years back and it was also pretty clean after a sound scrubbing!


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## SG-Rocker (Dec 30, 2007)

That's a stunning combo - never realized how good white tolex would look !
Now you got me thinking about a re-tolex project !

What speakers are in your cab ?

Does anyone sell repro cabinet badges ? I'm looking for a JCM 800 LEAD 1960 badge !


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## xbolt (Jan 1, 2008)

SG-Rocker said:


> That's a stunning combo - never realized how good white tolex would look !
> Now you got me thinking about a re-tolex project !
> 
> What speakers are in your cab ?


Cheers,
Yours looks untouched...very cool find.

This cab and another white slant 4x12 I've had since the 80's both came with G12-65s...My old white one now has 2 EVM12L paired with the 65s which I've used since 2000 with my Mesa Tremoverb...
I also have a few other cabs and the 2203 sounds very nice but quite different through all of the different speaker types.
A 77 4x12 with Blackback G25Ms another JCM800 with 2x G12-70 and 2xV30 and a 1965A 4x10 with G10L-35s...


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## SG-Rocker (Dec 30, 2007)

New addition to my family, the stack is complete!
The slant cab is packed with G12-65 Heritage reissues and the straight cab has mid 90's UK Greenbacks.

They sound exactly the same individually and collectively they are neighbourhood armageddon.

Now to wait for the family to get me the SoloDallas Storm pedal for birthday / Xmas / Father's Day


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## isoneedacoffee (Oct 31, 2014)

SG-Rocker said:


> The slant cab is packed with G12-65 Heritage reissues and the straight cab has mid 90's UK Greenbacks.
> 
> They sound exactly the same individually and collectively they are neighbourhood armageddon.
> 
> View attachment 30873


Congrats. That setup looks killer! I'm interested that you don't hear differences between the cabs and their different speakers. Can you tell me more about this please?


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## BSTheTech (Sep 30, 2015)

What do you guys use to clean the dirty tolex? I now have two 4010's I need to clean up. Can't resist a deal.


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## SG-Rocker (Dec 30, 2007)

I used diluted Mr Clean and a stiff bristle brush.
Follow up with a rag dampened with clean water and done!

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## Budda (May 29, 2007)

Yeah JCM800 stack!


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## SG-Rocker (Dec 30, 2007)

isoneedacoffee said:


> Congrats. That setup looks killer! I'm interested that you don't hear differences between the cabs and their different speakers. Can you tell me more about this please?


Right now I'm packing up and getting ready to move from Petawawa to Edmonton.
Once I get settled in I'll try to do an A-B video.
I also hope to meet some like minded individuals and perhaps put a band together!


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## Budda (May 29, 2007)

SG-Rocker said:


> Right now I'm packing up and getting ready to move from Petawawa to Edmonton.
> Once I get settled in I'll try to do an A-B video.
> I also hope to meet some like minded individuals and perhaps put a band together!


Military Im guessing? I grew up 20m from pet haha.


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## Adcandour (Apr 21, 2013)

Congrats on the new amp. I had an appointment to snag one yesterday (1980 combo in brown). I decided the funds should really go to finishing my basement.


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## Budda (May 29, 2007)

Doublepostdoublepost


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## Budda (May 29, 2007)

While we're talking 800's...


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## SG-Rocker (Dec 30, 2007)

Nice 2203....
The CSA Marshalls really boggle the minds of those not familiar with them.

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## Budda (May 29, 2007)

SG-Rocker said:


> Nice 2203....
> The CSA Marshalls really boggle the minds of those not familiar with them.
> 
> Sent from my SGH-I727R using Tapatalk


I'm not technically proficient, I just know they differ than the US models. I also know they sound great and I love mine!


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## SG-Rocker (Dec 30, 2007)

Unique to CSA Marshalls:

- metal power and standby switches
- extra board inside for additional fuses and diodes
- no tap for 16 ohm cabinets
- shipped with EL34s

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## Budda (May 29, 2007)

SG-Rocker said:


> Unique to CSA Marshalls:
> 
> - metal power and standby switches
> - extra board inside for additional fuses and diodes
> ...


Turns out I knew about everything except the additional board haha. How hard is it to set the american models to a higher wattage with the 6550's?


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## SG-Rocker (Dec 30, 2007)

The transformers dictate the output moreso than the tubes. 6550s tend to be tighter, apparently that's why Zakk Wylde stuck with them.

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## ezcomes (Jul 28, 2008)

So then...are the extra diodes 'clipping' and for distortion...or are they for filtering?


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## SG-Rocker (Dec 30, 2007)

I'm going to say filtering as they are in the power supply circuit.


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## ezcomes (Jul 28, 2008)

SG-Rocker said:


> I'm going to say filtering as they are in the power supply circuit.
> 
> 
> Sent from my SGH-I727R using Tapatalk


That would make sense...


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## dcole (Oct 8, 2008)

SG-Rocker said:


> Ok mods done. I must say that the power tube wiring is pretty shite from the factory. The melted wire insulation is original and not my doing. I can foresee a future project of replacing the power tube sockets and cleaning up the wire dress.


I once opened up an old Marshall JMP mkII 50 watter that had the treble bleed cap installed on the master volume rather than gain pot since factory. The treble was terribly loud at low volumes, as you can probably tell why.


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## SG-Rocker (Dec 30, 2007)

Oh wow, that would be brutally ice-picky.

I do find the treble is nasty with the preamp volume under 6, I might desolder a leg on the bleed cap and see the difference it makes.

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## dcole (Oct 8, 2008)

SG-Rocker said:


> I just picked up the only mod this amp will ever see...
> 
> 
> 
> ...


If you do a lot of this type of work (bias), there is an effective method that works well without installing 1 ohm resistors in the cathode. First, you measure the dc resistance of each half of the output transformer while the amp is cold and unplugged. Once you fire it up and let the amp warm up, measure the voltage across each half of the output transformer. Next, do a little V over R and you have you plate current calculated. This way, you can bias any amp without modifying it. Take proper precautions while working with high voltage as well.


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## dcole (Oct 8, 2008)

SG-Rocker said:


> Oh wow, that would be brutally ice-picky.
> 
> I do find the treble is nasty with the preamp volume under 6, I might desolder a leg on the bleed cap and see the difference it makes.
> 
> Sent from my SGH-I727R using Tapatalk


Exactly. That was the customers complaint and easily confirmed. How that amp made it through 40 years of life without anyone opening it up to see why it was so bad is beyond me. Or it was played cranked to the 9s its whole life.


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## SG-Rocker (Dec 30, 2007)

Here's a question....
How should caps bleed down after shutiing down the amp?
This amp bleeds down to ~10 volts within 15 seconds.
Caps are original FWIW.

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## dcole (Oct 8, 2008)

ezcomes said:


> So then...are the extra diodes 'clipping' and for distortion...or are they for filtering?


If they are power supply diodes you are referring to then they are for what is called the Peak Inverse Voltage (PIV). This refers to the maximum voltage a diode can withstand in the *reverse*-biased direction before breakdown. Its easy, cheap and rather common to stack diodes to double this rating.


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## dcole (Oct 8, 2008)

SG-Rocker said:


> Here's a question....
> How should caps bleed down after shutiing down the amp?
> This amp bleeds down to ~10 volts within 15 seconds.
> Caps are original FWIW.
> ...


They should bleed down fairly quick due to the circuit arrangement, but its been a few years since I have had my hands in a Marshall now, so I can't remember how quick it should be. 

If you fire it up with all the tubes pulled, then turn it off, check how long it takes to drain. I would expect it to hold high voltage as there is now no path to bleed with the tubes pulled.


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