Marshall JCM800 2203, 82/83

[Racerxrated]

Best way I can sum my experiences with 5-10 82-83 2204/2203s is, as a few others have stated, those years have higher voltages than 81s or 84 and after leading to more aggressive amps. All of my amps from those years had 500v PTs. Not one measured below that number. They weren't as high as the early 70s beasts, those SLs had PVs of 525v at times...but right at 500, 505v or so. Really killer sounds and like Mike (46-2) stated, you can always filter to a lower number but you can't raise it to a higher one.
If I were looking for a JCM 800 2203/4 I'd definitely wait for an 82/83 to come knocking.

 

[Racerxrated]

The known change between vertical and horizontal input amps that does make a very noticeable difference is the voltages. Vertical input amps are generally in the 440-450v range and when you get to horizontal inputs they bump up to 480v or higher. So preamp voltage also goes up. So overall harder, brighter more aggressive and less gain. You can certainly use drop resisitors to lower the preamp down to the earlier voltage, but not the plate voltage. the 2204's had a huge voltage swing with early versions at 380-395v, late '82 up to 440-450v and horizontal inputs 460-480v.

All the 1982 2204s I had were over 500v. 1983s also. Maybe they all were mid 82, to mid 83? But they were all in the same 500v range.

 

[anomaly]

So lower voltages mean the tone is generally looser, spongier I guess? Higher means tighter or stiffer sounding? Makes sense considering what tweed mode does on a Mark IV. It also reduces the wattage down considerably.

 

[2dor]

I literally got a 1983 JCM800 2203 in today. Haven't measured it yet.

It's in pretty good condition for its age; has got a very funny serial number lol. Would have been close to impossible to get the numbers that way if I had wanted to.

 

[BesaMoogie]

Interesting. Mine has them.

Ok, I was always thinking that missing screen grid res were a sign for low voltage 2204.

 

[BesaMoogie]

So lower voltages mean the tone is generally looser, spongier I guess? Higher means tighter or stiffer sounding? Makes sense considering what tweed mode does on a Mark IV. It also reduces the wattage down considerably.

Generally yes. In the 2204 with low voltage, one 10k dropping resistor is missing, bringing the voltage to about 320v at the PI node.

When voltage went up, Marshall sometimes added the 10k resistor again, and sometimes they did not.
So you end with 2204s with higher voltage throughout the amp and 2204s with higher voltage only at the powertubes PV

 

[FourT6and2]

Ok, I was always thinking that missing screen grid res were a sign for low voltage 2204.

Nope. Marshall has just always been pretty inconsistent. They did random shit for no apparent reason. If they were out of screen grid resistors that day, instead of waiting for more, they were like, "No worries, Janice. Button the amp up and ship it."