Electronics Check

This stage is reached when the printed circuit boards (pcbs) have had all the components fitted to them. If the check reveals no fault, then it's safe to apply power.

Modification

First there is a modification to do to the Open Motion Controller, the large pcb.

The two surface mount resistors R11 and R14 have to be changed to a new value.
The nearby R15 must be mounted on the underside of the board.
R13 (not far away) has to be removed.

Unless you are confident that you can remove soldered components from a through-hole plated board, ask for some practical help.

Continuing with the modification, there's a new tiny pcb to which two pins must be soldered.

An easy way to get the pins lined up is to use one of the empty IC sockets on the main circuit board. Push one end of a pin into a contact of the IC socket, and push the second pin into another contact, 0.3 inches away. Then slip the two drilled holes in the new tiny pcb over the top of the two pins (component side up) and solder them in place.

Fit this assembly into the two holes in the main pcb, where R13 used to be. Orient the tiny pcb so that it occupies the space above the diode D1, and solder it in place into the main pcb using the R13 solder pads.

Solder a lightweight wire to connect from the bottom right-hand corner of the tiny pcb, to the 0 V point above the Reset pushbutton.

The two surface mount resistors need a heat sink. Take some double-sided adhesive heat conducting sheet and cut a square to cover the bottom of the provided heat sink. Bend Q4 away from the surface-mount resistors, then put the heat sink on top of the two surface mount resistors.

The sheet adhesive is pressure-sensitive, so the only way to get a firm fixing is to press down really hard between thumb and forefinger for a while.

Electrical tests

All modified, you can do the electrical tests. You will need a resistance meter for this. The ideal tool is a multimeter with a tone that indicates a closed circuit.

Open Motion Controller

The tests are intended to check that connections exist where there should be connection, and that no connection exists where it should not. The tests are not exhaustive. Refer to the diagram below to identify pin numbers.

With one probe on 0v, put the other probe on IC1 pin 4, a beep is OK.
With one probe on 0v, put the other probe on IC2 pin 7, a beep is OK.
With one probe on 0v, put the other probe on IC3 pin 11, a beep is OK.
With one probe on 0v, put the other probe on IC3 pin 31, a beep is OK.
With one probe on 0v, put the other probe on SD pin 3, a beep is OK.
With one probe on 0v, put the other probe on SD pin 6, a beep is OK.
With one probe on 0v, put the other probe on screw terminal 2, a beep is OK.
With one probe on 0v, put the other probe on screw terminal 4, a beep is OK.
With one probe on 0v, put the other probe on screw terminal 6, a beep is OK.
With one probe on 0v, put the other probe on screw terminal 8, a beep is OK.

With one probe on 5v, put the other probe on IC1 pin 8, a beep is OK.
With one probe on 5v, put the other probe on IC3 pin 10, a beep is OK.
With one probe on 5v, put the other probe on IC3 pin 30, a beep is OK.

With one probe on 3.3v, put the other probe on IC2 pin 14, a beep is OK.
With one probe on 3.3v, put the other probe on SD pin 5, a beep is OK.

NB: there are test points on the OMC for 5 V (next to the reset switch) and 3.3 V (next to the SDCARD)

With one probe on 0v, put the other probe on IC3 pin 9, test for a beep while the reset button is pressed, and no beep when it is not pressed.

With one probe on 0v, put the other probe on Screw Terminal 1, NO beep is OK.
With one probe on 0v, put the other probe on 5v, NO beep is OK. (For those without a beeping meter, this should be somewhere in the 3-10 kΩ range).
With one probe on 0v, put the other probe on 3.3v, NO beep is OK. (For those without a beeping meter, this should be somewhere around 140 kΩ).

With one probe on Screw Terminal 3, put the other probe on Screw Terminal 5, a beep is OK
With one probe on Screw Terminal 3, put the other probe on Screw Terminal 7, a beep is OK

If everything is OK, plug in the three ICs taking care to see that each pin enters each contact correctly.

New ICs have their pins set a little wider than the socket, and it is helpful to bend them to be truly parallel. This can be done by placing the IC sideways with the pins on a flat surface and gently moving the IC body upright. Repeat for the pins on the other side.

The pcb is now safe to have power applied to it, and is ready for the next stage, flash programming of the microprocessor (IC3).

Dual Stepper Motor board

There is little to test on the DSM board:

Set your meter to measure in kΩ. With one probe on GND (the screw terminal nearest the corner of the board, or the contact surrounding one of the mounting holes in the corners), put the other probe on the upper (i.e. most easily accessible) pin of the black ribbon connector nearest the screw terminals. Hold the contacts in place until the value settles down — this may take up to 30 seconds. You should get a stable reading of around 73 kΩ (plus or minus 1).

Note that if you have added any jumpers to the board, the measured resistance will be lower.