Marshall 100w JMP (2203) - output switch

[Sir Cuitous]

Question about the speaker impedance switch on this amp. Forgive my lack of experience with these amps, but the impedance switch looks more like a socket than a switch. Is this switch selected with some kind of shunt or jumper? Any general opinons on the playability of this amp?

[drewl]

The old ones were just a jumper or "shunt" encased in a plastic handle.
Don't know when they switched to a switch...think it was a little before the JCM800's or in the late 70's.

[Sir Cuitous]

I believe this amp is dated 1979. The amp was given to me and I was told it does not work. I don't have a speaker to test it yet, but it passes visual inspection. It may be as simple as connecting that switch. I suppose I can use some solid wire to test it and ultimately replace the receptacle with a toggle. It's too much power for my needs, but it may sound good.

[Enzo]

You can still buy "Marshall impedance selector plugs" from various sources. it is a jumper wire in a plastic knob. There is a square window hole in it that exposes one of the impedance numbers on the female part. So the proper humber is off to teh side of the actual jumper position.

http://www.tubesandmore.com/cemirror/inv/P-H502.GIF

That is from AES at www.tubesandmore.com for $8.95.

Without the plug, there is no speaker connectin from the OT to the speaker jacks. DO NOT play the amp this way.

A piece of bare 12ga solid copper wire as used in house wiring will usually work. Bend a short piece to fit.

[Sir Cuitous]

Thanks for the info. I will get the selector, but I will most likely test it first with some wire.

[Alex R]

- sometimes people soldered them up behind the socket so it was permanently 8 ohm or whatever. Not a bad idea as it means you don't get problems with bad contacts on the plug, though of course it ties you to the one impedance.

If it ever made any sound in its current condition then a soldered-up selector is what you likely have.

[drewl]

Yeah I lost one for my '73 years ago.....got the replacement.
Back before I worked on amps I took a piece of buss wire and wrapped it around the switch and secured it to the mounting screws....

Anyway, if this amp is too much power for you I'll take it off your hands;)

[Sir Cuitous]

OK, so I finally tested it out. It has Awesome tone. It was simply that the previous owner did not have the speaker selector and did not realize it was missing. The volume pot is a little scratchy and the imput jacks need to be replaced, but otherwise it's perfectly functional and fun to play. It's still more power than I can use, but I already have buyers lined up. It's amazing what people will just give away.