6040Z controller

[Doddy]

My opinion : The BoB should be suited for the mod.

Squinting at the PCB images, it appears that there's a SIL resistor package that pulls-up the parallel port "inputs" (X/Y/Z/E-STOP) to the onboard 5V, and the pin-pairs allow the connected switches to ground these through to ground. Apart from a failure on the board there's not much to go wrong.



Power OFF, disconnect limit switches, disconnect computer cable:

1) Verify the three pads marked "GROUND" have low resistance between each (100% confident they will)
2) Verify continuity between pad marked "11" and pin 11 on the DB25 connector. Yes, the long row are pins 1-13, the short row 14-25. The pins are usually marked in the connector, but at 51 years old I can't read them. Pin 13 is the one closest to the jack socket that you want to add.
3) Verify continuity between pad marked "12" and pin 12.
4) Verify continuity between pad marked "13" and pin 13.
5) Verify no* continuity between pad marked "11" and the adjacent "Ground" pad.
6) Verify no* continuity between pad marked "12" and the adjacent "Ground" pad.
7) Verify no* continuity between pad marked "13" and the adjacent "Ground" pad.

(* : "No" - certainly a lot higher than a few ohms - these signals are pulled to the onboard supply line, so there can be/will be some measurable resistance but would expect this to be >1kR)

8) Verify high resistance between pad marked "11" and "12" (high = at least 2kR, depends on the SIL resistor values)
9) Verify high resistance between pad marked "12" and "13" (high = at least 2kR, depends on the SIL resistor values)
10) Verify high resistance between pad marked "11" and "13 (high = at least 2kR, depends on the SIL resistor values)

If you're prepared to test "powered" - reconnect all power, computer and switches:

11) X-Axis switch "closed" - voltage on pad "11" = 0V (measured, with respect to the ground plane on the board.
12) X-Axis switch "open" (or removed from board) - voltage on pad "11" = 5V.
13) Y-Axis switch "closed" - voltage on pad "12" = 0V (measured, with respect to the ground plane on the board.
14) Y-Axis switch "open" (or removed from board) - voltage on pad "12" = 5V.
15) Z-Axis switch "closed" - voltage on pad "13" = 0V (measured, with respect to the ground plane on the board.
16) Z-Axis switch "open" (or removed from board) - voltage on pad "13" = 5V.

If all these measure okay - and I'm confident that without a failure on the board that they will, then the BoB is okay.

As an suggestion for your experience yesterday, with nothing working, double-check that your supply voltage to the BoB was present - the BoB depends upon the pull-up to the local board supply to get the "logic 1" (switch open) sense level.