JMP Lead 50 Watt 1975 w/Big M Cabinet

Discussion in 'Member Classifieds' started by fretted friend, Dec 16, 2019.

  1. fretted friend

    fretted friend New Member

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    IMG_3262.jpeg Hello everyone! I am new to Marshall Forums. I owned a music store for over 30 years specialized in high-end acoustics, now retired. I did sell amps, lots of them including Marshall in the early 2000's. But truth is, I know very little about this Marshall history etc. Thank goodness for this Forum!

    I recently bought an estate with guitars and amps. One in particular is a 1975 MK2 50watt Lead with a "Big M" cabinet (sides are straight, grill is slanted and loaded with 4x12" Rola speakers. Both head and cab are single-owner and extraordinary clean, near mint IMO.

    My question is, the amp has a master volume knob on the back of the head. Was this a stock feature? I can't find any images of the same. Please advise. I may be posting this rig for sale in the near future. Thank you in advance for any and all information to help me identify and hopefully come up with a price so I can place it on the Classified Forum.

    Your fretted friend,
    Michael IMG_3262.jpeg
     
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  2. DaDoc

    DaDoc Well-Known Member

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    No, they didn't..But that is a common modification on amps from that era. It's a fairly easy mod to return to stock by a competent tech, but it leaves a hole in the back of the amp, which will lower the value over one that has never been modded. Hope this helps!

    By the way, that's a really nice looking '75..Amps from that era don't often look that clean..Most cool! :cool:
     
    Last edited: Dec 16, 2019
  3. fretted friend

    fretted friend New Member

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    Thank you
     
  4. tce63

    tce63 Well-Known Member Premium Member

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    AS @DaDoc says, NO

    Just like to say :welcome: to the forum, a great place
     
  5. fretted friend

    fretted friend New Member

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    Here’s a pic of the back panel
     

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  6. fretted friend

    fretted friend New Member

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    Thank you! This is why I spent the last thirty years in this business, the people
     
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  7. Nik Henville

    Nik Henville Well-Known Member Premium Member

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    Damn...

    That's as fine a piece of loudificatin' as I ever did see.

    :hippie::pirate::uk:
     
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  8. fretted friend

    fretted friend New Member

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    It certainly blew my mind to see a 40+ year old rig in 100% original condition (except for master vol), pristine inside and out.
    BBAF46E7-9892-4105-A5C3-A8163CC4AD1C.jpeg F12D5C08-6006-4C30-A330-C549B92C2E0A.jpeg D2CC04AF-BC58-4D3D-9D3F-EBB5858D8633.jpeg D2CC04AF-BC58-4D3D-9D3F-EBB5858D8633.jpeg F12D5C08-6006-4C30-A330-C549B92C2E0A.jpeg AA25A7A7-ACA6-4E01-8292-D8EFF03FC3A4.jpeg BBAF46E7-9892-4105-A5C3-A8163CC4AD1C.jpeg
     

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  9. Chrome

    Chrome Well-Known Member

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    I have the 76 version of your amp. it also has the master volume mod but instead of a new hole, we utilized the extra speaker jack hole as I only play with one cabinet, now I'm looking for another cabinet to complete the stack so may have to go to this. instead. but it's by far the best sounding amp I own.
     
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  10. Chrome

    Chrome Well-Known Member

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    let me know if you price, or sell separately as I may be interested in the cab.
     
  11. fretted friend

    fretted friend New Member

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    Thank you Chrome. I'm in the S.F. Bay Area, if I sell it will most likely be a local transaction. I digging the tone, now that I have a Dr. Z for Country, a Boogie for Blues and of course the Marshall for all that CRUNCHES! Happy New Year to All!
     
  12. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I feel it is my duty to make you aware of the fact that those original blue canister capacitors are original to the amp and are very much due for replacement. Plan to do that soon. If they should fail it can turn a modest cost service visit into an expensive service visit.
     
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  13. fretted friend

    fretted friend New Member

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    Thank you for the heads-up on the caps, are they more likely dry?? That said, I have been playing with the master and both channel volumes (single and jumped) I’m trying to see if I can get any kind of clean tone at any volume, I’m just curious. Ive had no luck! Is that because this amp just doesn’t do that ? i.e. produce a clean tone? FYI Ch 1 is brighter ch 2 has the bottom end, That’s all good. I just can’t get a clean tone. Also, Just like the caps, it appears that everything including the tubes are original. like I said I am new to the Marshall world in spite of the fact that I am a 60s refugee. In addition to the caps I will re-tube the unit as I move forward. Thank you again! Oh! I checked out your website, beautiful work!
     
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  14. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Well, it's been modded to some degree, that's why it's got a master volume control, so its gain range could certainly have been altered, too.

    Turn the master volume up all the way and you should be able to get good clean tones out of it, using the front panel volumes to adjust the output.
    It should be clean until things start getting pretty darned loud that way.

    If you're getting an appreciable amount of distortion out of it before the volume control reaches noon, then the modder increased the gain of the circuit.

    The thing about the capacitors is that they were designed for maybe a 20 years service life. And they're over 40. Oh, they can still work, but it's like
    driving around on very old low mileage tires. The tires are still likely dry rotted.

    I could get into the technical reasons why the capacitors are sure to be degraded by now, but if that isn't really necessary, just know that they're old
    and have long outlived their guaranteed lifespan. They're due for replacement and won't be getting better as they get older.

    Should one fail it could cause damage up to and including destroying the power transformer. (If the wrong fuse is in the fuse holder.)
     
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  15. fretted friend

    fretted friend New Member

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    Thank you once again. I understand about the caps I did take some physics in college and I also discovered and checked out a great thread here on the forum.
    http://www.marshallforum.com/threads/replacing-old-filter-caps-and-why-you-should.15452/

    Okay, now I need to ask where you might recommend to get them, any particular mfg? How about a recommendation for tubes, i.e. 6550s. Lastly, would you suggest that I disconnect the two wires to the master volume to see if that might help to clean up tone?

    Gratzie gratzie!
     
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  16. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I actually had a conversation with the capacitor manufacturer that has all the intellectual property rights and trademarks of the old Daly capacitor brand, which were the capacitors that are in your and most all other vintage Marshalls. They're evaluating the business case for making new Daly capacitors of the same types, and for that reason I'd personally want to hold off on replacing capacitors for a couple of months in the hopes that this actually happens.

    I'd use new Daly capacitors if they were available. In a few months, they might be. I'd wait and see, for a little while at least.

    Both ARS and F&T make suitable replacements.

    Even though I recapped both my Marshalls with ARS caps recently, if new Dalys come available I'll put Dalys into both of them.

    Outlets for ARS and F&T capacitors include but are not limited to Mojotone, Tubesandmore, and Antique Electronics Supply. I just Google search for "Marshall amplifier parts" and several hits come up that will give you sources to buy these parts.

    For 6550 tubes, I think the Sovtek 6550WEs are good. I swapped my original GEs for the Sovteks and really could not tell any difference. The Sovteks do have the same general bottle size so I didn't have to swap the tube retainer clamp for the smaller EL34 size.

    Mullard (reissue) EL34s seem to be a good choice for EL34 replacement. The same can be said of the Tung-Sol (reissue) EL34s as well.

    Personally, I'm setting up my 1959 for KT66s at the next tube change. Just because I want to try them. I already have them, I just have to finish rebuilding the amp to try them out. (Full restoration project.)

    I'm not going to recommend disconnecting the master volume. You need to have a qualified and experienced Marshall tech take a look at it and map out ALL the changes made to it, and then decide what direction you want to go in.
     
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  17. fretted friend

    fretted friend New Member

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    Ciao Matthew, just curious, any update on availability of the Daly caps?
    Thx in advance
     
  18. kuli

    kuli Active Member

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    To get clean tones out of an amp like that, you have to roll off the volume of your guitar.
     
    Last edited: Mar 18, 2020
  19. ampmadscientist

    ampmadscientist Well-Known Member

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    La corsa per cambiare il condensatore! Dipende: Se il condensatore perde o si deforma, è possibile cambiarlo. Se il condensatore ha poche ore, non è davvero necessario cambiare l'originale. Alcune persone in questo forum cercheranno semplicemente di venderti cose, ma potresti non aver bisogno di tutte queste cose.
     
  20. neikeel

    neikeel Well-Known Member

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    I agree with AMS above.
    The preamp does not appear to have been modded, however the PT is a replacement.
    This era of lead JMP50 will be quite bright and gainy.
     
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