Service Upgrades and a Detailed Look Inside an '84 Marshall JCM800 2203 Halfstack
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- Опубліковано 5 січ 2024
- A while back I acquired a very nice and clean 2203 halfstack from '84. This was a great year for the amps but not so much for the cabs as the G12M-70's have a pretty bad rap. This was a transitional year for both the cabinets and the heads.
The 2203 amplifier would first see the DI jack installed on the rear panel during this year. In 1984 the vertical input models would also be discontinued in favor of new construction methods which would put all the inputs horizontally as they would be mounted directly to the PCB. There is a lot of conjecture online about the vertical input models being better built and easier to work on... it's all nonsense. The main difference between models other than construction is that there are less 50/50 can capacitors in the 100W horizontal input version. We will save that comparison and the technical aspects between the two for another video.
1984 would also end production of the G12-65 and you would see many G12M-70 speakers fitted in cabinets with 260W badges meant for the G12-65. Fortunately the G12M-70 would be short lived and permanently replaced by the G12T-75 speaker.
I really love the stock 2203 sound so the preamp circuitry is left stock while I replace the electrolytic capacitors and make some improvements to the input shielding, heater circuit and ground scheme for maximum reliability and the least amount of unwanted noise.
Check out my website for more information www.purgasound.com
Celestion date codes and a T-number database can be found here
www.bygonetones.com/celestion...
Marshall date codes, would be the last letter in serial number
A July 1969 - Dec 1970
C 1971
D 1972
E 1973
F 1974
G 1975
H 1976
J 1977
K 1978
L 1979
M 1980
N 1981
P 1982
R 1983
S 1984
T 1985
U 1986
V 1987
W 1988
X 1989
Y 1990
Z 1991 - 1992
Sounds bad ass man. Nice ass guitar too. Love your videos man, been a while. Keep em goin man, ill always thumbs up...
My favorite tech channel, wicked stuff as always!
Thank you !
Didn't know about the dummy plug trick. Excellent video, thanks!
I have a 1985 jcm800 50 watt non master volume and it’s by far the best sounding amp I have ever heard and I also have about 10 other high end tube amps ! They all have a purpose but that one blows all of them away by far
Found your channel recently. Love the content!
Just a classic sounding amp. Not as gained out as a lot of modern stuff but so mean and punchy.
Every video i watch makes me wish you were closer to AZ so i could have you give my amps a once over
First time viewer. Very impressed by your approach and that tip with the dummy plug was really cool. The amp sounds great. You should have a very happy customer. Happy New Year.
Love the low gain input tone. Nice work! Cool speakers but not my first choice.
Awesome work and instruction my man !!
G12-65's John Sykes speaker of choice. He used them in his cabs with the MESA Collesuems [180 watt] for the early stuff including WS and Blue Murder. Ive had a MK I, MK III combo, MK IV head and a 3 channel Dual Rectifier all great amps but nobody would work on them and i have A+ industry techs. Had to sell them as not a question of if but when they need work. Dave Friedman built me a Kitchen Sink 2203 in 2011. My weapon of choice. I have a 2009 non bias issue 2K DSL 100 and recently a 2011 Bad Cat Cougar 50. Love your videos. I was schooled in Electronics and bias my own but mostly don't have the patience for the hard stuff. Cheers.
ua-cam.com/video/P8mkJmVUXfc/v-deo.html 1978 Blackback cab.
ua-cam.com/video/iBi9F8PoWUQ/v-deo.html
oh the larry ground scheme
You sir are a magician.
My 50 watt is the most brutal amp I have ever owned. My Mark IV is brutal but my 84 is just a beast. Throw a yellow OD on from and EMGs and it is a beast. A 100 watt is waaay to much
17:45 that’s Rat Catcher. Sucks you aren’t in GWAR anymore. Hail Pusty. 🤘
You are awesome 👍! Keep going 💪
I miss my old 2203
I miss picking them up used for $300-400 back in the day. 4x12's too...
Nice work on the amp. Those g12m70s sure do smooth out that top end. Probably chalk that up to the medium sized magnet and the big dust cap. I could live with them for bluesy rock and roll, but I'd much prefer a Greenback, v30, or g12-65 for anything more aggressive.
Looking forward to your talk about more or fewer filter caps in JCM 800's. I have fewer: 1986, horizontal inputs. I always wondered if it would be worth adding the missing ones. If you were to choose a year of JCM 800 that had the best design/specs, what would it be, and would it make sense to alter mine to meet that design? I definitely could use better grounding. This amp is noisy. I sent you an email asking where you are located - your website doesn't say. Wild guess: Chicago?
You had me after 20s...when you stated that Mesa suck to work on...
I just watched this a couple hrs ago. 🤣🤣🤣
Ha! Had to reupload, there was some problem with the audio
they used these black caster all the way through 1983 my friend.
Cool video! I would’ve liked a bit more presence and treble in the tone for my liking however but each to their own…
I think you can chalk some of that up to those g12m70s.
@@CharlesWillisBonsai maybe but he did have presence on zero and treble on 3 so not all to do with speakers. Amp sounded congested imo
Could you do a video on that ENGL poweramp in the back there?
Par Excellence!
and the speakers were 65 or 70 watters for the most part through 1983
It's hard to tell if the speakers soud bad. Everything else in the chain is bad ass.
Noice !
Brent what's your opinion on the JCM 800 combos? Worth it for bedroom play and jamming or no?
For bedroom jamming it might be better to try one of the new 20W models. Those old 50W combos can still be really crazy loud but they sound great. There's no circuit difference between the combo and the head.
So, what's the verdict in m70's? Here they seem a bit weak in the bass (no big deal) and a bit fizzy in the highs (bigger deal). But I don't dislike them at all.
I trim some of the excessive low end by the mic technique. That being said, not a ton of bass in these. They are just extraordinarily plain. Once they get up to higher volumes the EQ adjustments don't do too much. Not a fan. They're kind of a junk speaker in my opinion. There is definitely worse stuff out there.
Since those new grounds aren’t isolated from one another, what is the point of making them separate?
The subject can get quite complicated but generally what we're trying to do is eliminate possible ground loops. When all of the grounds are to the back of the pots there are multiple paths to ground and they cross over each other. This can cause ground loops and create buzz. Moving all the grounds as I did to the chassis is not a perfect solution but it does create a better path than the back of the pots. Getting into why the order is important is more than I can explain in a comment. That's a subject we'll have to revisit later thanks for watching!
I’ll stick to my V30s, K85s, G1265s, and Greenbacks. I’m sure you can get decent tones with these speakers, but they’d be pretty far down my list when such better speakers are available.
I’d bet those speakers would sound better with something like a Bassman.
I agree
i think g12m 70 sound better than the g12t75
Just to let you know, the amp depreciated after you drilled holes on the chassis
By how much? These aren't old Ferrari's. Anyone who wants to make money should be buying stocks, not amps.
This is why you never send your Mesa to a normal amp tech. Pack it up and ship it to Petaluma, even if it cost way more its much bettee than hearing your amp tech cry about it, and it'll actually get fixed right the first time.
That makes sense.