1974 JMP Super Lead 100 MK II

Discussion in 'Let's Talk Vintage' started by bstoner, Jan 14, 2020.

  1. ampmadscientist

    ampmadscientist Well-Known Member

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    The chassis label says this amp was built for Japan, 100 volts AC.
    So you should probably have a knowledgeable technician check the power and voltage before you try to play it.

    [​IMG]
     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    What is your B+ voltage?
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    I smell the PT burning...
     
  4. bstoner

    bstoner Member

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    It appears the PT has already been replaced. I have been using the amp for weeks now with no issues.
     
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  5. ampmadscientist

    ampmadscientist Well-Known Member

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    You should check the voltages and make sure it's OK.
     
  6. MickeyJ

    MickeyJ Well-Known Member

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    and,
    Ive heard them sound better with the volume on 8, not 11.
     
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  7. bstoner

    bstoner Member

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    How is that done?
     
  8. ampmadscientist

    ampmadscientist Well-Known Member

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    If you are comfortable measuring high voltage then you need a volt meter.
    If you are not take it to a qualified Marshall tech and get a checkup on it.
    Because of the state that it's in that should be checked out.

    [​IMG]
     
  9. matttornado

    matttornado Well-Known Member

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    with my 74, I tried and used every possible PPIMV and the pre phase one over the years.

    with my particular amp, using an attenuator is the way to go.

    Don’t believe that when a LarMar master volume is dimed, it’s “essentially out of the circuit”. That’s BS. even if you dime it, it’s still there. The added wire and pot makes a difference
    and changes the sound.

    I didn’t mind it playing at low bedroom volume because to me, that type of master sounds best.

    I struggled when playing live though, i ended up cranking the master anyway and used a Power Break.

    Now the master is gone and the magic is back!
     
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  10. matttornado

    matttornado Well-Known Member

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    i’m no way a purist. i totally get how it works wonders to make it a practical amp for gigs. like i said, used master volumes off and on for decades! they’re great just not for me. i started out with using a power break when i got my 1959.
    that kind of set the standard and spoiled me i guess.
     
  11. neikeel

    neikeel Well-Known Member

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    [​IMG]
    Eueuw!
    That is not nice.
    Are you actualy plugging that into the mains and the other end to a guitar that you are holding metal bits of?:ugh:
     
  12. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Yeah, I'd name that one Jane because it looks like a Calamity is distinctly possible any time you plug it in!

    It's pretty scary looking in there, but the 1959 I got super cheap a week ago is even worse. Whatever hack was inside it used the octal socket pin 1 on
    each power tube as a tie point for high voltage. Well...if you have metal base 6550s, that's the pin that the base is tied to. So the amp has its own way of preventing people from stealing your tubes while it's turned on. 500 volts on the tube bases!

    Needless to say, that's going to be one of many things that need to be addressed.
     
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  13. bstoner

    bstoner Member

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    It's not the prettiest, but it sounds great. A good effects loop would make it even better :) Oddly enough there is very little noise even when cranked.
     
    Last edited: Feb 16, 2020
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  14. Exotic

    Exotic Well-Known Member

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    glad u got it

    so if u had it now,how would u make it sound like van halen?
     
  15. Obi Plexi-nobi

    Obi Plexi-nobi Well-Known Member

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    To start? Change the filter cap cans to 'Dave Friedman VH' Lead filtering specs, add the 'fat cap' on the board at V1/V2, variac the AC to about 89 volts, etc., all while realizing the VH sound isn't really super distorted after all. I'd probably use a Palmer Speaker simulator to draw a line out to +8/-8 pitch shift as well. It's all out on the internet now.
     
  16. Obi Plexi-nobi

    Obi Plexi-nobi Well-Known Member

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    RACKSYSTEMS wrote:
    "... Look, unless all you guys are trying this on a 12 series amp you have no idea what it sounds like. Also none of you have a power transformer that is doing exactly what his does either. It sags about 70+ volts with normal wall voltage dimmed and 50 some volts with a variac on it. Also unless you are listening with original 6ca7s everything gets thrown out the window.

    The real key to get the right sound also is the treble cap. His amp has been restored with all mustards and a 560pf lemco treble cap and a 500pf little red cap out of a 69 era amp for the mixer bypass cap. Also the amp has been rewired with all original period correct wire out of another plexi.

    Now I have said this before the amp is biased to like 85ma with normal wall voltage and then dropped with a variac to 90 volts. This will bring the bias down to around 50ma. Now the way the feedback is set up and filtering works well with this setup. I was told the amp now sounds like it use to back in the day..."

    RACKSYSTEMS wrote:
    Split cathode V1a 250uF/820,V1b .68/820
    All coupling caps are 0.022uF,Bright channel coupling cap is 0.0022uF
    470k mixer resistors
    500pf [red out of 69 amp] mixer bypass cap

    Bypass cap on V2a is .68uF and a 220uf to 470uf
    33k/560pF lemco tone stack combo
    100k NFB resistor at 4 ohm tap
    220k bias splitter resistors
    0.1 uF cap on presence control
    .022uf output couplers

    Filtering is:
    2] 100uf's f&t in series mains
    2] 32uf's f&t in series screens
    1]100uf lcr phase inverter
     
    Last edited: Mar 1, 2020
  17. Obi Plexi-nobi

    Obi Plexi-nobi Well-Known Member

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    In a nutshell, it (the EVH plexi) looks to be mostly '68 specs, but with some of Marshall's later-era filtering & the later-era negative feedback (NFB) specs added in.
     
    Last edited: Mar 1, 2020
  18. Obi Plexi-nobi

    Obi Plexi-nobi Well-Known Member

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    Steve Stevens:
    "... Yeah, the amp that I recorded "Rebel Yell" with was an old Marshall, not a plexi but a’71 metal face and that amp had been shelved. It was really my workhorse. It was an amp that I had years before joining up with Billy Idol. I recorded "Rebel Yell" with it and then for some reason it had stopped working and I left it in storage. You know, I had acquired plexis and stuff by then. But the guy who does all my gear, Dave Friedman at Rack Systems, started talking with me about modding one of my amps because he’s learned a number of things, especially since he works on Eddie Van Halen’s gear and he’s seen the early amps that Van Halen recorded the early stuff with. And he said there’s no big mystery to that particular amp [sound], he could do that to one of my amps. So I was like, "Done deal! Take that amp that’s not working."

    "... When I got it back from him I was amazed by the sound of it. It didn’t have any added gain stages to it; there was no big mystery to it. It was just a couple of resistors changed. He suggested running on a Variac and lowering the voltage. There’s one particular solo on the record, on a song called “Small Arms Fire,” where you hear it and go, “Wow, that sounds like early Van Halen” and it is THAT Marshall..."

    https://www.premierguitar.com/artic...w-his-solo-album-and-his-gear-1?Page=2&page=2
     
  19. 8bit Barry

    8bit Barry Member

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    To the OP - Are you still happy with the amp? I’ve seen a 50w mk2 I’m keen on... how does it’s sound? I’m worried it’ll lack bass or have excessive treble
     
  20. MickeyJ

    MickeyJ Well-Known Member

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    you should play this bitch long and hard just the way it is.
     

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