'73 Marshall JMP Lead 50 Restoration

Discussion in 'Amps & Cabs' started by Torren61, Sep 12, 2021.

  1. Torren61

    Torren61 Member

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    I bought this Marshall head a year or two ago. I probably should have passed on it with the replaced output and power transformers and the other wiring that was done but I didn't.

    I didn't realize how much was missing or replaced until I went to the Marshall forum and was enlightened. That left me with a choice of either selling the amp and taking a loss because I would inform the prospective buyers about everything I knew or having a restoration job done on the amp. Because it was the early '73 JMP with a hand wired board and not the printed circuit board, I chose the former.

    So, it had a catastrophic event at some point that lead to the power transformer burning up. It had been wired in a weird way that it never really had much crunch to it but instead had high headroom and really nice cleans. I just wanted it back to stock as much as possible.

    I couldn't find a period correct Drake PT or OT so I decided to go with Metropoulos transformers. The feet/gliders were wrong so I found the right ones. The knobs were wrong so I got the right ones as well as the right resistors, power and standby switch, indicator light, correct bolts and PT transformer mounting bracket.

    Here's what it looked like before:

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    Here's what it looks like now:

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    It sounds SO much better. It has the CRUNCH we all love about Marshalls.

    Well, I didn't have a 4X12 Marshall cab so that was a problem for me. I wanted a '73 cab to go with the head. I looked around but there were none near me that I could find so I went to Reverb.

    Vintage Marshall cabs are expensive to buy and expensive to ship and most sellers won't ship at all. And when they do, a LOT of them are just empty cabs. I had to settle for an empty cab. I bought one in decent shape but I still needed speakers.

    I found some '72 Celestions but they were in the UK and they weren't G12Ms or G12Hs, they were G12S. The "S" stands for "small" magnet. "M" stands for "medium" and "H" stands for "heavy". Just as there are folks who like heavy magnets over medium magnets, there are folks who prefer small magnets so I bought them.

    One had an advertised tear in the diaphragm and two had misaligned voice coils so i had to send them to a fellow in FL who restored them as opposed to re-coning them. I didn't want them re-coned. He repaired and restored them by cleaning them up, aligning the voice coils and re-gluing the diaphragms.

    I patched the grill cloth a bit, replaced missing screws and installed the speakers and re-wired the cab with correct wire. I also installed a bit of felt to keep the back panel from vibrating against the center cab post. The casters were missing so I had to find those, which I did.

    AE5A862F-102E-4D41-B02E-510DF91E9364_1_105_c.jpeg

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  2. Torren61

    Torren61 Member

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    New old casters:

    81DF52D2-5E13-4E48-A72E-AAFC6ADB3E5E_1_105_c.jpeg 16FF3306-FCF2-4C6B-9E56-13EEF9757F84_1_105_c.jpeg

    Here's what the cab looks like:

    522CCB8D-15FC-4189-8B6A-00B1537344A9_1_105_c.jpeg

    I thought i had a pic of the head and cab together but it's either on my other computer or I'm gonna have to drag out the head and cab for a photoshoot today, lol.
     
  3. Go Nigel Go

    Go Nigel Go Well-Known Member

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    Nice work, I would have done the same as you and fixed it up myself. Point to Point wiring is pretty easy to work on, and once you over pay for something there really isn't any better way to salvage the situation than just fixing it up yourself, and get the value out of it by using it. Something like this is definitely worth having around.

    Never owned a big Marshall like this myself, but if I ever find one I can afford easily I would probably jump on it. It isn't really necessary for someone who plays at home or small venues (like me...) but I still want one anyways. Go figure... :D
     
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  4. Torren61

    Torren61 Member

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    Well, you can play it at home with the right equipment. I have several things to tame the volume yet play it at full power. I have a Fryette Power Station. that's a reactive load amp with a pair of 6L6 tubes. So I can run an amp into that and out of the Fryette into a cab. It can accommodate 4,8 and 16 Ohm amps and cabs. It has an effects loops, too, so I can insert effects between the first amp and the Fryette. I can turn down the volume on the Fryette allowing me to dime the Marshall. Additionally, I can run a low power amp into the Fryette and crank the Fryette to as much as 50 watts. I do that with a couple of Champs.

    I also have a Rivera Silent Sister isolation cab loaded with a Celestion Alnico Gold 50 watt speaker. It's not totally silent but it's pretty quiet. I also have a Two Notes Captor X. That's a reactive load for my computer. It's also an attenuator. Using it as an audio interface with my computer requires using impulse response cab simulators.

    I hope you get to play through an old Marshall some day. I predict you'll get hooked and you won't be satisfied until you get one. :hmm::D
     
  5. Go Nigel Go

    Go Nigel Go Well-Known Member

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    Indeed... :cheers:
     
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  6. ruster1

    ruster1 Active Member

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    Keep it.. fix it.. mod it.. enjoy it.. !! I purchased a beat up Marshall major in college from a bouncer who used it as a bass amp and i traded in some chemistry books for it.. lol.. had it for a long time as i had not speaker cab and it was a night stand next to my bed.. finally got to fire it up after buying a JCM900 cab and it was soooo loud and sooo clean.. pedals were not cutting it.. the tolex wash trashed.. i later sent it to David Bray to put new trannies and convert it to super lead circiut.. had Mojotone retolex it.. (this was 2004 i believe) .. oh.. i was in love with the KT-88 tubes so i had David split the bias and put 2 x KT88 and 2 x EL34 in her with a PPIMV in the polarity location and she RIPS.. big fat plexi sounds.. its already cascading and jumpered internally.. looks the part.. sounds awesome.. ENJOY every minute of it.. (Oh.. i still kept all the original parts just in case i had to sell her).. but its not going anywhere.. I might get a Freyette PS and see how she sounds on 10.. with the added effects loop would be nice to add a touch of delay.. i do need some greenbacks however and keep my eyes open for a cab..
     
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