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Old 11-02-2021, 07:20 PM   #2
bobxyz
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Join Date: Aug 2014
Location: Boulder CO
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From your picture, it looks like you have a special brand new pandemic edition of the MS-2 with a v3.57 PCB (special being tall non-anodized case due to supply chain delays and shortages), correct?

The disc in your hand is the one you want - the other one is a 4G63 factory disc for a Mitsubishi or Hyundai. You have a B20, which (I believe?) rotates the disc in the opposite direction as a B21/B23/B230. If so, the orientation shown in your picture is correct.

To swap the disc, undo just the center bolt, remove the washers, and slide the disc out sideways. Aligning the flat of the D closest to the black sensor makes it a bit easier.

You can think of a pullup resistor as a helper spring, but for electrical circuits. For the CAS, you want 2 separate 1K ohm resistors to help the tach and cam signals swing from 0volts all the way up to 5volts:
- one connected between the CAS inner/cam signal and MS +5Vref
- one connected between the CAS outer/tach signal and MS +5Vref
Without the pullup resistors, the tach and cam signals would barely move from 0volts. The resistors can go in the wiring harness, or within the MS2 box.

The order of the pins in your picture is correct - when viewing the connector sticking out of the CAS, the pins from left to right are:
- ground
- +12v during run and start
- tach signal (outer disc sensor)
- cam signal (inner disc sensor)
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