I'm a little confused at looking for a Marshall schematic

[mort]

I'm not very familiar with the Marshall line up, and I need a little help finding a schem.


My buddy wants me to build him a 50W Plexi (circa 1968) w/ a master volume. Is there a good drawing available for that circuit?


Any help is appreciated...

[Jazz P Bass]

This is about as close as it gets.
Link: http://www.drtube.com/schematics/marshall/1987u.gif

[mort]

This is about as close as it gets.
Link: http://www.drtube.com/schematics/marshall/1987u.gif

Would that need the MV added to it, or is it already in there?

[Jazz P Bass]

Can't read a schematic, huh.
Seriously though, no, there is not a master volume on the amp.

[mort]

Can't read a schematic, huh.
Seriously though, no, there is not a master volume on the amp.

Ha!

I do rely on some things being labelled, as found in some schematics, but I wouldn't need a symbol legend. At this point in the game, I'm an avid assembler with a budding potential to know wtf I'm doing

[Jazz P Bass]

Yeah, some manufacturers certainly do not have techs in mind when they document there equipment.
'Oh, you want things labeled?'
Good luck with the amp.

[big_teee]

There were two versions of the 50 Watt MV amps.
Both are the 2204 model.
The 100 Watt version is the 2203
The earlier version was the JMP, 2204 the Later was the JCM800 2204.
Those both had the pre Phase Inverter Master Vol.
Not to be confused with the Later, add on PPIMV, or Post Phase Inv. MV.
http://www.el34world.com/charts/Sche..._50w_2204u.pdf
http://www.el34world.com/charts/Sche...l_50w_2204.pdf
The two amps are different.
The JCM version has the Cascade preamp, the JMP version does not.
The JMP 2204 Came along in 1975, the JCM version was some later.
I built the JCM 800 2204, but also added the PPIMV.
So mine has both the pre and post master volumes.
It works great.
T

[Enzo]

Or here, explore this:

Marshall Amp Heaven Schematics - JTM-45 JCM-50 JCM-600 JCM-900 JCM-2000 JTM-100 JMP IBS Jubilee Valvestate Bluesbreaker

[oc disorder]

May I suggest for the first time round that you look at a kit ?
For example
Ceriatone Amplification
Not sure if any of these have the master volume.
There are basically 2 types of master (and variations within that!).
The pre-amp master where the pre-amp tubes are cascaded ie overdrive within the pre-amp section and the second type a master volume just before the power valves so the whole amp (both channels) after the phase inverter/splitter can be turned down. The latter type seems to be the most popular one.
A friend with limited skills in amp building built a Ceriatone kit and was pleased with it. Only had to help him a couple of times and although I didn't give him very good marks on his soldering skills the thing worked and of course now I'm responsible for his addiction!!
There are other kits by different manufacturers but the Ceriatone one is the only one I've seen first hand.
They seem to only provide layout diagrams but there are lots of the old style circuits in circulation.
In the schematic section here , there are sticky links to many sources of Marshall schematics.
Using the search engine on this board often unearths little gems too!