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1979 Marshall JMP MKII-Ohm selection

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  • 1979 Marshall JMP MKII-Ohm selection

    I just picked up a very original Marshall JMP and wanted to change the OHM selctor from 16 to 8...I have never owned a Marshall before and thought I would just be able to turn the Ohm selector to 8...however is isnt budging (there are screws on either side)...before tinkering with it I thought I would ask the proper way...

  • #2
    You can go to http://metroamp.com/store/ and order a replacement for it if you need one. Just be careful messing with that sort of thing if you've never done it before. You want to make sure there is no stored voltage in the caps before getting into the wires.

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    • #3
      Have you tried pulling it? I can't vouch for a 79 head, but on my early 70s Super Bass head the Ohm selector you pull out and then put back in for the Ohm rating you want. I am very drunk and may be speaking out of my arse.


      Edit - I may not be telling porkies. Have a look at the pictures on this link, it may give you an idea http://www.marshallforum.com/marshal...0w-1977-a.html
      Last edited by shobet; 09-13-2008, 05:00 PM.
      Fwopping, you know you want to!

      VI VI VI: the editor of the Beast!

      There are 10 kinds of people who understand binary. Those who do and those who don't.

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      • #4
        Originally posted by shobet View Post
        Have you tried pulling it? I can't vouch for a 79 head, but on my early 70s Super Bass head the Ohm selector you pull out and then put back in for the Ohm rating you want. I am very drunk and may be speaking out of my arse.
        My 74 100W Marshall was like this. Had to pull, then turn and re-insert. I think the other guitarist in one band I was in had the same head as you and he lost the "knob" at a gig before we were to start playing. I seem to to remember that his amp would not put out anything without it. He was lucky that another guy with a Marshall showed up to play in the band after use and lent him the one from his amp for the gig.

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        • #5
          Like others said. Try pulling it straight out like a plug. Then rotate it to the position you want and plug it back in. That is how my old super lead was.
          Scott
          Be without fear in the face of your enemies. Be brave and upright, that God may love thee. Speak the truth always, even if it leads to your death. Safeguard the helpless and do no wrong.

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          • #6
            My 77 is the same...... It dosent turn. you gotta Pull it out......
            "Now remember, things look bad and it looks like you're not gonna make it, then you gotta get mean. I mean plumb, mad-dog mean. 'Cause if you lose your head and you give up then you neither live nor win. That's just the way it is. ":JOSEY WALES

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            • #7
              thanks guys...im gonna give it a try

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              • #8
                So, thats more or less a safety feature then?
                My 9200 Poweramp isn't like that, it's just a slider.

                I didnt know those switches were like that. I learned something new, thank you!
                'Howling in shadows
                Living in a lunar spell
                He finds his heaven
                Spewing from the mouth of hell'

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                • #9
                  Wait till you see one of the old Bulgin power sockets they used to use!
                  Fwopping, you know you want to!

                  VI VI VI: the editor of the Beast!

                  There are 10 kinds of people who understand binary. Those who do and those who don't.

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                  • #10
                    Sometimes they fit a little too tight and you have to use a set of pliers to pull it out. My `77 master vol. Marshall is like this.

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                    • #11
                      The dial ohm was used on the Plexi the JMP mark ll are pull out and reinsert.

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