Marshall JMP 1987 questions.

Discussion in 'Amps and Cabs' started by Tuff, Jan 3, 2008.


  1. Tuff

    Tuff Member

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    I might trade my vox for this Marshall JMP model 1987 with a serial number *****R printed on the front of the head. The thing is, according to this site for example: http://www.superiormusic.com/page024.html

    Amps made between 1979 to 1981 might have the serial printed on the front. But that seams wrong according to the thing that the serial ends with R. Which should according to the site mean it was made '83?

    Also, are these really the original switches? It seams a bit odd. And isn't that a master volume?

    And the final really big questions are, how old is it? Or is it even a "real" Marshall?

    *you can see that the serial is printed right below the left corner of the on/off switch*
    [​IMG]
     
  2. John Phillips

    John Phillips Member

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    That's not an R, although it could very well be a K (1978). It was certainly made in the '77-'81 period.

    The power switch has been changed (the standby is original), as has the handle (or at least the ends, which should be gold-plated metal), and I'm suspicious but not certain that the vinyl has been re-done, because it isn't tight enough in the upper corners of the panel cut-out... although it could just be unusually badly done, since the corner protectors don't appear to be replaced (it's difficult to get them as neatly riveted as that)

    But it does look like a genuine 1978 model 1987 - non-MV, there is a volume control for each channel, not 'Preamp Volume' and 'Master Volume', and four inputs not two.
     
  3. Tuff

    Tuff Member

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    Thanks a lot for that very useful info. Does this mean that if i trade this along with a 4x10 Marshall cab its quite a good deal for my almost brand new Vox AC30CC2? Keep in mind i live in Sweden, the prices are a bit different.

    Also, as i play mostly old stuff like AC/DC, Hendrix, EVH etc this has to be a Much better amp for my musical style along with my Gibson SG?

    And is it hard to make a master volume since i play alot at "bedroomlevel"?
     
  4. John Phillips

    John Phillips Member

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    I would, unless the Marshall needs significant work. The AC30CC is a good-sounding amp, but it's not going to retain or increase its value like the old Marshall will, and although not terrible, it's not a good bet for long-term reliability either. Even now a used AC30CC2 is worth a bit less than the Marshall and the 4x10". (At least in the UK.)

    Yes :).

    It's not hard, but it doesn't really give you the 'right' tone at very low volume.

    There are several MV mods, the best of which are 'post phase inverter' and involve very little modification to the amp. The simplest (the 'cross line' MV) is literally just one pot and two wires, fitted in the second speaker jack hole, and although not the best tonally it's acceptable. There's a better type (the 'Ken Fischer' MV) which involves a little work to the circuit board but is otherwise non-invasive. Both of these leave the amp dead stock when the control is turned up full. Don't mod it more than that... if you need to, you need a different amp.

    Alternatively you can use an attenuator (but again, it won't sound that great right down at bedroom level) or a good pedal - which surprisingly, can do. Or you can use more than one method at once.

    If you do get it, it would probably be a good idea to have it checked by a tech and possibly fully overhauled - it may need the filter caps replacing since it's thirty years old. (It will sooner or later anyway.) If you're doing this, that's the time to have any possible MV mods done as well. Personally I would also have the incorrect power switch re-replaced with the right one, but I'm just fussy ;). Do that, and the Marshall should be reliable for the next thirty years too...
     
  5. jlummaa

    jlummaa Member

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    Your amp can be '82. I had 2203 (100 W MV head) that was made '82 with exactly the same cosmetics like that amp excluding the handle. That handle can be original too as the JCM 800's had that style handle and Marshall started to make JCM 800's a bit later on the same year. I think the switches are original.

    Edit: Sorry mistyped some year numbers.
     
  6. Tuff

    Tuff Member

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    Thanks again John!

    I think i want to go through with the trade after all but i am a bit suspicious since i really don't want an amp needing to replace pretty much everything. Moving from a nearly brand new Vox to a 30-year-old amp might be tricky.

    An other problem is that the trader lives over 500km away and i most definetly want to test the amp before i buy anything. But that might just be my problem! :)

    As for the MV-mods i might get back to you when/if i do the trade. But as you said, its not really fair to the "correct"-sound.
     
  7. Tuff

    Tuff Member

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    But how about the front printed serial?
     
  8. jlummaa

    jlummaa Member

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    Yes, sorry forgot that. I am guessing yours may still be a '83 if i had almost similar amp made in '82. I mean it wouln't be totally impossible.
     
  9. Tuff

    Tuff Member

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    Off course not! But it just makes me a bit suspicious. I mean, what if it is a copy made in much earlier years? I don't know enough about marshalls to tell...
     
  10. John Phillips

    John Phillips Member

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    It's maybe not impossible, but everything else - including the typically 70s, not 80s, knobs - looks like 1978 to me. I've never seen a JMP from later than the start of '82 anyway.

    The power switch is definitely a replacement. It's from a Selmer Treble'n'Bass (or at least the same type of switch). The neons in the Marshall switches often fail - although they can usually be repaired if you know how - and the correct type of switch is surprisingly hard to find.

    It's not a copy. It wouldn't be worth it to make one to that degree of accuracy. The thing to worry about is whether it's been hacked or badly repaired inside - many have, unfortunately.
     
  11. Tuff

    Tuff Member

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    You seam to know you´re Marshalls. I totally agree about that the switch looks like a Selmer one too. But didn't the original 1987 have the dip-switches and not these big square ones? It cant be possible to put the "old" ones back in without it showing.

    Yea i most definitely have to go there and look at it before i do anything with this trade. Just take a peak inside and see if its okay.

    *edit*
    How will the 4x10 effect the tone since pretty much everyone uses 4x12?
     
  12. Tuff

    Tuff Member

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    I just got an e-mail with some requested pics by me from the guy.

    [​IMG]
    Serial
    [​IMG]
    It appears to have been sold originally in Sweden. Thats seams genuine to me!
    [​IMG]
    And the handle.

    They didn't really help! :S
    According to the guy he hasn't touched anything for the 6 years hes has it.
     
  13. Gavin

    Gavin Supporting Member

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    I thought that Marshall started putting the serial number on the front of the amps by the on/off and standby switch in 1980.
     
  14. Tuff

    Tuff Member

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    Maybe you're right but i cant find any proof of it!
     
  15. John Phillips

    John Phillips Member

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    Yes, it is definitely an R, definitely 1983, and the handle is therefore probably original. But interestingly it's a 100W cabinet - with the top vent - so I'd guess they were using up excess parts for the export market, as shown by the fuseholder panel. It's certainly the latest JMP I've seen.

    The big rocker switches came in in 1977, all the late-style JMPs have them, apart from some other exports (Canada, I think).

    The 4x10"s are great little cabs, obviously not as huge-sounding as the 4x12"s, but the same sort of impression. They look pretty silly with a full-width head on top though :(.
     
  16. Tuff

    Tuff Member

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    Thanks a lot for all the help John!

    As for the head looking silly i agree but since i have a quite tight space for it at home i think it will be great!

    As for the part that it is from '83 i cant really figure out if its a good thing, or a bad thing! But it cirtenly looks original and i have to say that if it is. It seams pretty unique! I wonder if it has EL34 or 6550's.... ?
     
  17. Gavin

    Gavin Supporting Member

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    The Hsitory of Marshall book, page 144 states 1979-1981. Just looked it up. I remembered the picture on that page.:)
     
  18. Tuff

    Tuff Member

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    Damn it, now I've gotten confused again!

    I still cant let go of the facts that it seams very odd!

    It has a 100w chassis, JCM type handle and switches. According to http://www.drtube.com/marshall.htm the JMP series was discontinued in 1981. And according to the serial this one is from 1983!

    This doesn't make any sense! E-mailed Marshall about this to see what they say.
     
  19. John Phillips

    John Phillips Member

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    EL34s. 6550s were only for the US market.

    I had never seen a JMP from later than early 1982 before either, but I have no doubt that this is original. It's simply that Marshall were quite economical about using up old stock, and if they had left over 'export' spec chassis made up, they continued to ship them until they ran out, if necessary using 'wrong' parts (ie the 100W box and JCM800 handle) to complete them.

    The switches (large rocker style, if not the actual power switch) are completely correct for late-period JMP from 1977 onwards.

    Being from 1983 rather than 1978 is a good thing - the caps will likely not need changing quite as urgently, and it will have the vastly superior rotary impedance selector instead of the awful pull-out/fall-out/blown output transformer type.
     
  20. Tuff

    Tuff Member

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    I so hope you're right! I'm still looking forward to hear what Marshall themselves have to say.

    Once again, thanks John. I have to say this is quite fun! Lets just hope Marshall doesn't give us another surprise!

    As for the 83 rather than 78 i think so aswell. But i still have to say its odd... Never seen a so "young" JMP. Its still older than me though... :rolleyes:

    BTW, i just found this. This is not the same guy selling but the JMP looks very similar: (might be a 100w, doesn't say)
    http://vendolin.se/Annonce_Detail.asp?rub=60023&annonceid=5259692
     

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