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I have a Laser FD-100 that doesn’t work. the stepper motor just vibrates instead of moves. I took it out and greased it and still nothing. There are 3 pins on the board that look broken. What are they for?enter image description here

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  • A stepper motor usually has multiple "phases", if it vibrates instead of moving, then one or more of them are not properly driven (for whatever reasons). And I can see corrosion on your board (which likely is the reason, somewhere some connection is not working), but no broken pins - the three pins behind the LED are likely probe points or some external connector, and if the LED didn't cover the writing, we could maybe even tell you what they are for.
    – dirkt
    Commented Nov 14, 2022 at 6:22

1 Answer 1

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After hitting reset, try typing CALL -151, and then typing each of the following at the monitor prompt on a line by itself:

C0E9
C0E1
C0E0
C0E3
C0E2
C0E5
C0E4
C0E7
C0E6
C0E1
C0E0
C0E3
C0E2
C0E5
C0E4
C0E7
C0E6
C0E1
C0E0

Each odd number after the first should turn on one of the four stepper motor phases, and the even number immediately below it should turn it off. Doing the phases in this order should advance the head toward the inside of the disk by four tracks. Depending upon where the head is located, activation of the first phase may or may not be audible, but each phase after that should cause a slight click.

The code which is in the boot ROM only knows how to blindly move the head outward until it hits the end stop. If the head is already at the outermost position, it will just move back and forth between the outermost two tracks. If the accesses above are performed in the order shown, however, that should advance the head inward by a total of eight half tracks, and the next time you boot the machine you should be able to see the head move outward again.

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