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  1. #1
    Les Paul Forum Member
    Join Date
    May 2019

    1969 Marshall JMP amp circuit board questions.

    1969 Marshall JMP amp circuit board,

    Does anyone know what size nuts are used for the circuit board ( nuts) ?

    And the Cheese Head Screw size for the Speakers.

    I still have the old style I bought from England years ago, but want some for stock.

    It's those tiny nuts, and the name of the metal washers that mount with them on the circuit board.

    The UK nuts are wider or thicker in height compared to the USA made nuts.

    Oh, and Jim Marshall told me he used red metallic enamel paint for the inspections on the terminals, not red dye.
    I told him I used all the red colored metallic Testors brand enamel paints to match what was on the amp. There is like 3 or 4 shades of the red metallic. And on the Filter Cap replacements I use a red & yellow Testors paint to mark the tops of the filter cap terminals using a Q-Tip, so no need to clean a brush., like the originals. It just looks clean and tidy when you paint the cap terminal circles on the F&T caps. When you look at all the Testors red/maroon metallic colors you will see how close they are. Seems the 1971-73 amps used a darker color than pre-1970, it was less metallic. Q-Tips work well to mark the terminals for inspection.

    Would be mighty kind to know what's in your mind,


  2. #2
    Les Paul Forum Member TM1's Avatar
    Join Date
    Jun 2003
    on the middle & bridge pickup of my L.P. Custom

    Re: 1969 Marshall JMP amp circuit board questions.

    I would take one of the nuts and one of the cheese head screws to Lowe's or a True Value Hardware shop and compare. Both are metric and you should be able to find a suitable match at either place as they normally have a number of bins of nut and screws in all sizes. Also check ebay..

  3. #3

    Re: 1969 Marshall JMP amp circuit board questions.

    All BA thread, like every other British amp back then. The board hardware is 6BA, output valve sockets and cap clamps 4BA, and the transformers 2BA. The speaker mounting screws are 2BA x 1". Very unlikely you'll find these outside the UK, but I can help if you're stuck.

  4. #4
    Les Paul Forum Member
    Join Date
    May 2019

    Re: 1969 Marshall JMP amp circuit board questions.

    Thanks Stu,

    I bought a massive brass box of the nuts and screws years ago from an amp service guy they were Nettlefolds UK boxes the same Jim bought. I notice3d the small circuitboard nuts are taller than modern replacement.

    There is a US company called , Jamestown Distributors and they have all old wooden board repair stuff, they can get any type of screws in brass or silicon bronze, stainless grades etc. They have wholesale pricing and good service if you gents ever need some stuff. Theyn have high end caulkings too. I bought some 10" long silicon bronze nails for 3" thick dock boards. And 6" #12 Copper Slate Roof nails for 1" thick slates on waterfront mansion I worked on years ago. It's amazing how much inventory they have. Monel Stainless drywall screws etc. Well worth a look if you ever need something special. The online site shows items in boxes of 100 etc. If I cannot find what I need I will ask Stu, Thank You. One of my early 1968 cabs has brass cheese heads, I never saw brass on other cabs, all my other one have steel screws. It's amazing how many cabs Jim signed over the years, he signed both of my 1972 cabs along with Ron.

    I just capped a 1975 SL 1959 Lead and they used Mustards but they used those small cheap round caps in the tone stack, I'm replacing them with the new Zoso Mustard Mica caps, they change the tone so much, well worth it. The Red Lemco are ok, but the new Zoso Mica's are killer from valvestorm., I put 32uF in the PI, Screens and Preamp, 50uF for the power caps. I was going to try 16uF on the screens. All the best,

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