Megasquirt 3 - MS3/MS3X case and card installation

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This page is intended for upgraders retro-fitting an MS3 or MS3X card to an existing Megasquirt unit.
For new builds, see the full Build Manual

Installing the MS3/MS3X into the case
For pre-assembled Megasquirt-3 units, these instructions may be of use if you need to remove the case to make internal adjustments.
For self-assemble or upgrades, this page should help guide you through installing the MS3 and MS3X cards and ribbon cables correctly.

Required parts:
Megasquirt mainboard
Megasquirt-3 compatible case (original Megasquirt-1 or Megasquirt-2 cases are too short for Megasquirt-3)
MS3 card
MS3 mounting bolt kit
Optional - MS3X card and ribbon cables

Plugging in MS3

  • If fitted, remove an existing Megasquirt-1 chip or Megasquirt-2 card. (If MS1 was fitted you will also need to add a jumper from S12C to JS9.)
  • Noting orientation, install the MS3 card onto the mainboard (V357 shown, V3.0 works the same) noting the 40pin socket/spacers that fit between the mainboard and the card. These ensure that the card sits at the right height to align with the end-plate.
    MS3 spacers

    Installing bolts

  • If fitted, carefully unscrew and remove the mounting bolt and nuts from U5 and Q11.
  • Install the mounting kit on U5 and Q11. The long bolt and a washer install from below. The short bolt and washer from above.
  • If required, additional washers may be installed between the standoff and the MS3 card to fine-tune the height.
    MS3 spacersSide view of completed assembly
    MS3 spacers lower viewLower view
    MS3 spacers upper viewTop view

    MS3X and ribbon cables
    If you are not using the MS3X, skip this step. However - ensure that nothing can touch or short the exposed pin headers. If in doubt fit a dummy ribbon cable plug.

  • Now would be a good time to set the "VR pots" to the recommended starting positions. See here.
  • Remove the hex mountings from the mainboard DB37 connector and the MS3X DB37 connector.
  • Fold the wide ribbon cable as shown (lower down) and plug in the two ribbon cables to the MS3X card.
  • Loosely screw on the end plate to the mainboard connector and then hold the MS3X card in place while loosely screwing it to the end plate.
  • Plug the ribbon cables into the MS3X card.
    Pay particular attention to the red stripe and orientation. Double check that ribbon cable plugs are aligned correctly. Incorrect installation can destroy the MS3 card.
    MS3 ribbons

    Fitting into case
    When used with the MS3X, the mainboard, endplate and MS3X assembly needs to be slid into the case as one unit. If the MS3X is not used, the case lid may be fitted independently.
    MS3X slotting into case

  • Having slotted the assembly into the case, screw in the four endplate to case retaining screws. The connector hex bolts may now be tightened up.
    MS3 case connector end
  • The USB-end end-plate may now be fitted, screwed onto the case and the connector hex bolts fitted.
    MS3 case USB end

    If you have a question, comment, or suggestion for this FAQ please post it on the forum.

    No part of this manual may be reproduced or changed without written permission from the authors.