Encoder Board

Tried to do a bit of reverse engineering on the encoder board. Pin 1 starts on the end of the board that bolts to the machine.

Pin Signal
1 Routes to 1B and 8B on Spindle Board Ground FWD/REV
2 Signal in from actual encoder routes toSN74LS123N
3 Signal out from encoder board to Pin 20 Parallel
4 Signal in from actual encoder routes to SN74LS123N
5 Signal out from encoder board to Pin 23 Parallel
6 Signal in from actual encoder routes to SN74LS123N
7 Signal out from encoder board to Pin 24 Parallel
8 Routes to Spindle Board Pin 6B V-
9 Unknown
10 Unknown
11 Routes to Parallel Port Pin 1 and Pin 12 probable Ground
12 Routes to 1B and 8B on Spindle Board Ground FWD/REV
13 Unknown
14 Unknown
15 Routes to Spindle Board Pin 4B and 10B V+ Positive Voltage
16 Unknown
17 Routes to Spindle Board Pin 7B Vtrip
18 Routes to Spindle Board through 4.7K to Pin 9B Enable
19 Routes Parallel Port Pin 11 *****Possible Control signal for Spindle *******
20 Routes to Spindle Board Pin 2B (S1 Signal)
21 Routes to Spindle Board Pin 3B (S2 Signal)
22 Routes to 1B and 8B on Spindle Board Ground FWD/REV

Links to the data sheets for the major players on the board:

DM74LS123 Dual Retriggerable One-Shot, there are two of these, probably handling the signals from the encoders. The Q outputs of these go to the Parallel port and the B inputs go to the encoders, not sure yet how this works.

MC1458 High Performance Dual OpAmps, most likely controlling the speed of the spindle, there are two on this board.

CD4070BC Quad 2-Input Exclusive Or Gate, somehow tied with Enabling the Spindle, might be a phase detector? Square wave to enable spindle, I dunno, it gets confusing pretty quick around this thing.

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