A note about those front and rear JMP era panels...

Discussion in 'Let's Talk Vintage' started by Matthews Guitars, Jun 28, 2020.

  1. Matthews Guitars

    Matthews Guitars Well-Known Member

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    As I've been accumulating more data in my quest to add more (and, eventually, hopefully every) variant of panel to the list of reproduction panels I can make for Marshall restorations, I've learned a lot. I'm going to share some of my findings with you because you might be interested to know, particularly if you are interested in restoring your old Marshall or even just trying to replace a badly damaged or missing panel for it.


    There are far more variations on the panel types than I ever imagined. I'm getting close to 50 patterns and I know I'm not done yet.

    Let's look at just a single family of panels. That'd be the JMP 100 watt rear panel for the Super Lead 1959 type, and, later, the 2203 Master Volume type.

    For one thing, I have realized that the original panels were screen printed in at least two separate stages. All of them share the "Made in England by Jim Marshall Products" legend, and those common printed features that apply to all 100 watters. Screening for the speaker icon, mains legend, fuse legends (where it's not dymo tape), and of course, the impedance selector legend. It appears that this was the common silkscreen for almost every 100 watt JMP made from 1973 onward until maybe 1979.

    The other legends, such as the block printed SUPER LEAD 100w or SUPER BASS 100w or SUPER TREMOLO 100w were all printed in a secondary process, and I say this because the common printed features I described earlier never change at all. They're always the same down to tiny details. Plus, the Super Lead and Super Bass and Super Tremolo screening was all over the place. I've seen some that were printed half an inch higher up the panel than others. If you look at a lot of old JMPs you'll see this very quickly.

    The screening for the voltage selector also appears to have been applied in a separate process, for those amps that were equipped with it.

    There are a fair number of optional ways to make the original panels and I mirror those changes with what I offer. Number of speaker jacks can be two or four. The mains voltage selector markings and punched hole can be deleted or added. IEC sockets were never standard on a JMP era 100 watter so I don't offer an IEC punchout because if your amp has it, it was installed by a technician and the installation has no standardized format. The options I provide for power input are Bulgin socket punchouts or grommeted, permanently attached line cord using a Heyco 5/8" OD double flatted D grommet.

    Those things alone require me to offer not less than eight different metalwork punch patterns for the 100 watt rear panels alone, for Super Bass and Super Lead rear panels, and not less than sixteen different variations on the artwork. (All the previously listed punch options plus I have to duplicate them for both Super Lead and Super Bass marked units.)

    The 1959T Super Tremolo unit is a special case. Although similar I don't classify it as a 1959 panel due to its differences. It's a 1959T panel and is its own thing.

    (I need to update my files to reflect that. I'm offering a Super Tremolo panel that actually shouldn't exist but it can work if you have just two speaker jacks and deleted the tremolo footswitch socket.)

    Going by the reference information available at amparchives.com, it appears that they didn't make them past 1971. The 1959T chassis punch pattern has a footswitch punch in the middle of the four possible speaker jacks, which if equipped, gives two speaker jacks on the left, and two on the right, of the footswitch jack. Some are equipped with all four jacks, others are not.

    The 1959 Super Lead used the rear chassis hole punch pattern of the 1959T Super Tremolo in those years where both models were available. It wasn't until the 1959T was discontinued that Marshall changed the chassis pattern to delete the unnecessary punched holes that would no longer be needed. I have not seen a 1972 chassis that was based on the 1959T chassis pattern so I assume that Marshall used up all the T chassis in 1971.

    The really strange thing about that is that while the 1959T and 1959 chassis shared the same back panel punch patterns from 1967 to 1971, the front of chassis hole punch pattern was always unique to the model. You don't see a 1959 that was actually built in a full spec 1959T chassis punched for eight front panel controls plus indicator and switches.

    But despite that, the Superlead 1959 chassis does have the extra punch for a fourth preamp tube socket (for the tremolo) for every year from 1967 to 1971.

    Marshall was consistent in one thing: Their inconsistency!


    Some rear panels have small dots printed on them. These are alignment dots so that the panel could be placed correctly for the sheet metal shop to punch the holes out more or less properly aligned to the artwork. The artwork was silkscreened first, punching came later.

    I have so far only seen those dots on amps that were made no later than 1974. I don't understand the specifics of when they were printed with dots outside of that. Nor do I know how consistently they were used during that time period.

    Even the presence, or absence, of the OUTPUT legend below the speaker jacks (bottom edge under the speaker icon) seems to be almost random for 1959 Superleads. Some have them, some don't. I haven't found the pattern for that yet.

    Apparently, MARK II appeared on the rear 1959 and 1987 panels in 1974. It seems that it should not be present prior to 1974 but I'm still looking to confirm that.


    I'll stop now. I'm getting pedantic the way I always do when seeking information.

    But you can see for yourself that by the time I've got most of the models figured out, I'm going to be a subject matter expert-in-training on Marshall front and rear panels!

    I'm starting to think Marshall never made more than 100 amps or so before they changed something!
     
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  2. pleximaster

    pleximaster Well-Known Member

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    Great and very cool info!!!

    Best regards!!!
    Plexi
     
  3. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Thanks!

    Adding more that I have derived from my research. You may find this useful as well.

    This represents my most recent determinations. It makes some of my previous comments incorrect or incomplete. Regarding the dots, for example.


    Panel application notes and appropriate years:



    Rear panel, 1959T Super Tremolo



    This panel application is for Super Tremolo units from 1966 to 1971. The front of the chassis is punched for eight controls (two for the tremolo circuit) instead of the typical six, plus switches and indicator light. The main chassis surface is punched for an extra preamp tube socket to support the tremolo circuit.

    The panels that are aluminum would apply to late 1969 onward. Prior to late 1969 a plexiglas panel is appropriate.

    The rear panel and chassis are punched with an extra hole for a DIN style socket for the tremolo footswitch. Speaker jack arrangement is either 2 or 4 jacks. In the event of a 4 jack type, the footswitch socket is located between jacks 2 and 3. Thus, the footswitch socket and speaker jacks comprise five equally spaced features 1.5 inches apart, center to center. The location of the speaker jacks, in the two jack version, is the same as the two speaker jacks found on a standard 1959 type with two speaker jacks. Power inlet may be Heyco grommeted (double flatted D punch) or Bulgin AC power socket (circular). Rotary jumper for line voltage may or may not be present.



    Rear panel, 1959, years 1966 to 1971:

    This panel shares the rear panel arrangement of the 1959T except that the footswitch socket is never punched in the rear panel.

    Location dots for features are present in the silkscreening. They may be mislocated by as much as a quarter of an inch in some cases.


    Rear panel, 1959, years 1972 onward:
    Mark II is added starting in model year 1974.

    Tremolo socket punch is now deleted in the chassis. The jack punch pattern becomes four 1.5" spaced jacks without interruption. Two jack versions exist as well. As per previous years, power options are grommeted cord or Bulgin AC connector. Input voltage jumper is present on some examples.

    Location dots are always present.


    Super Bass: Model 1992
    Aside from Super Bass replacing the Super Lead legend, in this model all features and changes are the same as for the 1959 Super Lead in every respect. The Super Bass was offered in every year as per the 1959. Treat SAME AS 1959 panels for all selection purposes.

    The only variations between Super Lead and Super Bass panels is the Super Bass legend and the serial number prefix changes from SL/A to SB/A.
     
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  4. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    Dont forget that in the early days we learnt as we went along.

    None of us were production professionals, especially in Amps, far from it, who in there right mind at the time thought it would end up were it is today.

    Keep up the good work mate.
     
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  5. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I'd SURE like to know exactly what outfit was providing the panel stock Marshall was using in the JMP era.
    All I can guess is that it was probably a company located in England.

    Since I'm going for maximum authenticity, I'd use the original material specification if it was available to me.
    (At a sane price point.)

    Ken, would you know if the panels were screen printed in house or was that done by a separate company?
     
  6. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    All i can say is that things like this was not done in house at all, other than Cabinets of course

    Screen printing back then was available, but were i do not know, as there many small companies all engaging in this sort of work.

    Hope that this is of some help.
     
  7. Big Mike

    Big Mike Member

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    You going to do JTM45/100 and black flag JTM100 panels?
     
  8. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Those are plexi panels. I'm only doing metalface panels at this time.

    I would like to expand into true to original plexi panels but I'm not going to say I'm going to actually do it until I have a production process
    worked out on them. I need an original panel to use as a paint sample reference. I've got nearly all the required artwork. I need to source
    appropriate materials at reasonable cost.

    So, yes, I'm interested in doing that and making preparations for it but it's a bit in the future.
     
  9. Matthews Guitars

    Matthews Guitars Well-Known Member

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    More things I'm trying to get to the bottom of:

    Apparently at some point in the early JMP years, the 4 input front panels changed font size. Trying to find out when. There were also some made with lines printed between the input jacks. Trying to identify the affected models and years for all the above.

    I'm not sure that I'm going to add new versions that do nothing but change a font size, but I'm not ruling it out.

    I'll need to know more before I put the effort into it.
     
  10. James Robinson-Wyatt

    James Robinson-Wyatt Member

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    This is all awesome stuff! I’m sure I’ll need one of your panels soon. Also I’ve got a 1972 1959T if you wanted some details on it? Inspection label is March ‘72.
     
  11. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I would LOVE some information on your 1959T!

    To make the front panels I need all the dimensional information required to make them.

    I work off the front panel dimensions, and not the chassis dimension.

    Please tell me the width of the front panel ( chassis out of the headshell box) and then, if you can do so, please place
    a ruler alongside the front panel with the zero of the ruler aligned with the left edge of the front panel. I need to see how far
    from the left edge each feature is. They'll be simple fractions of an inch, almost certainly. But the tremolo front panel is like
    no other in the JTM or JMP era. I have NONE of the information that I need to make it the right size and place the holes in
    the right locations.

    You may email me directly at cmjohnson@cfl.rr.com and my backup email is kaisergman@cfl.rr.com because sometimes the main email address
    doesn't always get messages. My ISP is to blame but they deny, deny, deny.
     
  12. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I've taken my first steps toward personally silk screening my panels. Starting with the 1959 type front panels, and adding more screen types as things move along.

    Silk screening is fun and rewarding when it's done right. Plus it's more durable (with the appropriate inks) than digitally printed artwork. For the digitalliy printed artwork,
    I have to pre-paint the panels in a urethane clearcoat, which gives a very good base layer for the digital printing ink to adhere to, and then I clearcoat over that, which
    is two steps I don't have to go through if I silkscreen the panels. The silk screened legends will hold up as well as clearcoated digitally printed art.
     
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  13. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Now offering six variants on the 50 watt back panel.

    DSC_7455_sm.jpg
     
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  14. mAx___

    mAx___ Active Member

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    Amazing work. I was looking for an original replacement for a '70 Major because both panels are in bad shape. They seem to be glued to the chassis. If so, how should I remove them?
     
  15. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I'm going to be offering Major panels, too. For the front, use a 1959 panel. With or without polarity switch, I make them both ways.

    For the Major rears, I need to confirm some measurements. It has not been my highest priority model but I do have work in progress art files for Majors.

    I'm not making them in plexi YET but that's in the works. But as your amp is a 1970, the metalface panels would be appropriate.

    To remove the old panel...got a filet knife? I just slowly work a thin bladed filet knife between the panel and chassis and try to avoid prying and
    bending the panel. Take your time and do everything you can to avoid bending it.

    If an original panel is kept sufficiently flat, I can clean the back surface and get rid of all traces of the adhesive, and then, if the back surface is adequately
    pristine, I can silk screen the back of the original panel. Often the front is too scratched and worn and would not look good enough if it were to be rescreened,
    but the back can be a candidate for screening. That way you are actually keeping your original panel but it looks like new.
     
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  16. TAZIN

    TAZIN Active Member

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    Another one for your list would be the rear panel on the first 1000 50w metal panel amps. It uses the S/ prefix rather than the S/A.
     
  17. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I'd need to see a photo. If the back panel chassis punch pattern isn't different, adding that is a trivial matter.
     
  18. TAZIN

    TAZIN Active Member

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    I'm not sure if the punch pattern is different...Ned B has a few of these amps perhaps he would be willing to look into that.
     
  19. MarshallDog

    MarshallDog Well-Known Member Premium Member

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    Those look great man!
     
  20. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Thanks! I've put a lot of work into developing them.

    I'm about to double the number of rear panel types I offer since every one can be made available with a punchout for a Bulgin power socket.

    I could actually use a single Bulgin socket for test fitting, if someone has one lying around they can sell me.

    I've also sourced a panel material that is MORE vintage correct to the originals than the material I've been using. It's pretty close but the new stuff is closer in appearance.

    I'm now starting to make the most popular panel types with real silkscreened legends. I'm doing the silkscreening personally.
     

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