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Thread: JP Trem Arm Bottom Grub Screw Adjustment

  1. #1

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    JP Trem Arm Bottom Grub Screw Adjustment

    Ok, so I know where the usual trem arm tension grub screw is behind the bridge under the intonation screws, and this typically tightens up the arm just fine. But, on one of my JP15s I simply couldn't tighten it any more without danger of stripping the hex head, and yet the bar still had too much play as well as some slop along the neck axis.

    I've always noticed another 1.5mm grub screw on the underside of the trem block but never messed with it on any of my EBMMs before. So I decided to stick a key in it and noticed it was extremely loose, so I tightened it up to be snug + 1/4 turn and voila - the slop and play in the arm disappeared. Arm still removes and inserts just as smoothly as before too.

    The main question is... how snug should this guy really be? Is it correct to adjust while the bar is inserted? I think there might have been a single thread in the past that mentions this adjustment but I can't find it for the life of me right now.
    Attached Thumbnails Attached Thumbnails JP Trem Arm Bottom Grub Screw Adjustment-trem_arm_bottom_grub-jpg  
    Current EBMM Guitars:
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    2014 JP6 BFR Koa
    2018 Valentine
    2018 JP15 BFR Eminence Purple

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  2. #2

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    Great subject to be honest. I've never tried anything with that hex screw. I don't quite understand what it actually does.

    Maddi would be the most appropriate man to instruct us.

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  3. #3

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    I always assumed it was there just to stop the bar going in too far. If there is another reason, we may never find out because Dudley has retired and if Sterling is not smoking meat his forum posts just amount to "HA!".

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  4. #4

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    The grub screw on the bottom works with the spring to hold the bottom of the trem arm steady, by giving it less room to move around once the end gets past the spring. Without it there, the arm can move in and out a little bit with the spring inside the groove on the end. The grub screw keeps it from going in farther than it needs to be.
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  5. #5

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    I took a closer look inside with a scope just because I was curious. I also played around a bit more and have some further observations.

    If the bottom grub is extremely loose you can jiggle the arm in/out of the slot and can feel the slop between the bottom of the trem block and the where the spring bar catches the bottom of the trem arm groove.

    In my case, I didn't notice any vertical play when I first started looking at this. However, I did notice lateral movement. If I would add some vibrato with the bar there was this sort of dead space in the middle of travel (neutral position). If I did it quick enough it would even come through the amp as a slight clicking as the trem arm rocked just a bit inside the slot.

    When adjusting the bottom grub screw, I found this seems to work best:
    - Leave trem arm inserted
    - Loosen the bottom grub a bit until the vertical play is noticeable
    - Slowly tighten bottom screw again while continuing to move the arm in and out (don't pull it all the way out - just wiggle it between the bottom most position and up to where the retaining bar provides resistance)
    - Stop once there is no more vertical movement
    - If vertical movement is gone but there is still a bit of lateral movement (like in my case) give it another 1/2 turn or so

    *If you keep tightening the bottom screw it will just end up pushing the arm up higher and higher and eventually past the retaining bar. So don't keep cranking expecting to feel more and more resistance.

    Just my two cents. It would be nice to hear from Maddi or EBMM on their preferred setup procedures regarding the JP trem arm adjustments.
    Attached Thumbnails Attached Thumbnails JP Trem Arm Bottom Grub Screw Adjustment-lower_grub_closeup-jpg  
    Current EBMM Guitars:
    2012 JPXI-7
    2014 JP6 BFR Koa
    2018 Valentine
    2018 JP15 BFR Eminence Purple

    My Youtube Channel

  6. #6

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    Yes, you've got it! The bottom screw is there to help set the depth of the bar against the retaining spring. If
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  7. #7

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    That's a great thread, I have to say =D

    JPXI Cardinal Red G57082
    JP12 Cherry Sugar G59225
    JP12 7 Cardinal Red F29322
    MAJESTY Glacial Frost M08083
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  8. #8

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    Great info! Thanks. Iím going to check the grub screws. Iím wondering if an incorrectly set grub screw has anything to do with my trems always turning into windmills over a while? I never take the trem bars out yet they always get loosey goosey after a few months (JP XI and Majesty)

  9. #9

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    Does this process work with other EBMM trems, e.g. the floyd rose? I noticed the FR on mine has both the side grub screw that controls the arm's lateral movement and rotational friction, and a screw visible when I take the back plate off. I'm assuming that bottom screw does the above? Controls how deep the arm can slot in and take out vertical movement?
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  10. #10

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    Quote Originally Posted by Mace13 View Post
    I’m wondering if an incorrectly set grub screw has anything to do with my trems always turning into windmills over a while? I never take the trem bars out yet they always get loosey goosey after a few months (JP XI and Majesty)
    In my case it did help with the arm swinging too loosely even with the top grub set as tight as possible. On my JP15 I had both excessive swing and that lateral wiggle in neutral position. On my JP6 BFR the swivel was fine, but there was that slight wobble in neutral position also. Adjusting the grub about 1 1/2 turns solved that too. My JPXI was solid without any movement, but the swivel was a bit too loose still. Again, snugging up the bottom grub just a tad helped with that too.

    I'd say go ahead and try it. Just keep monitoring the vertical travel to make sure you don't go too far and that the retaining bar still engages with the slot on the trem arm.

    One thing I am not sure of is the length of the bottom grub. It's hard to tell from scope pics due to reflections, and I was not brave enough to back it the whole way out to measure it. That's why I urge not to keep tightening it expecting more resistance. Given the physics of it it seems it's possible it could simply work it's way out into the arm cavity if you keep on going and going.
    Current EBMM Guitars:
    2012 JPXI-7
    2014 JP6 BFR Koa
    2018 Valentine
    2018 JP15 BFR Eminence Purple

    My Youtube Channel

  11. #11

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    Is there any possibility this bottom screw could prevent removal of the bar? I'm asking because I've never been able to remove the bar on my Artisan Majesty 7. The bar is easily removed on my other EBMMs (including 2 other Majesties) with the normal amount of force.

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  12. #12

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    Maybe. Did you try loosening the hidden hex screw on the rear of the trem block? I think that if that one is really tight it can make it difficult to remove the trem bar.

    If that’s not it, maybe give the grub screw is a turn or two to lower the grub. If it is too tight maybe it could press the trem bar notch into the little spring release thingy. Maybe back off the grub a turn and see if the trem comes out easier? If not, try another turn. Just count the turns so you can go back to original grub depth if it doesn’t make a difference

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