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I swapped back to "playing" with my believed-to-be working stepper motor driver board. Looking back, I found Nophead's comment about connecting the enable pin to 0V in order to get the indicating LEDs working. I established from the instructions that the enable pin was pin 5 on the IDC socket, but I didn't know which was pin 5.
After some internet hunting, I eventually managed to confirm the identification of the pins relative to the ribbon cable wires. I thought. I tried that, and got nothing. Hmmm. After some more hunting, I found that my reference website had been wrong - but they're in good company, as Asus apparently got it wrong in their manuals and on their own website! Luckily, this being a communication type connection rather than power, nothing drastic happened when I'd connected the wrong pin.
Using this website, I got the right diagram.
Wire 1 on the ribbon cable goes to pin 1 on the IDC, which is at the end of the row adjacent to the tab on the male connector, shown here as on the top left of the connector, and pin 5 is marked with a wire.
In order to test the stepper motor driver board's indicating LEDs, the pin on the board's connector corresponding to pin 5 on the ribbon cable is connected to ground.
Here is a photo' showing the connector pins 5 (enable) and 9 (ground) linked with a wire.
After arranging this, I plugged in and switched on power to the working board - sure enough the LEDs lit, but one green on one side and one red on the other. Is this correct? Anyone know which ones are supposed to light up?
I made up the 3 ribbon cables today for the 3 stepper motor driver boards. As I did so, it occurred to me that the cables connected these boards to the motherboard, and that as the cables had the same connectors on either end, the motherboard must have an IDC header, which is the part I ordered singly, instead of a set of 3.
Sooooooooo, I nicked the header from the motherboard kit in order to make up the second board.
On positioning the parts for the second stepper motor driver board, I was careful to orient the chip correctly!
When I cooked the second board, I did so withOUT the large electrolytic capacitors in place.
I cooked on medium to heat the board up and then as soon as the solder paste started to melt I turned it up to medium high. All told, it took just over 3 minutes. Nothing moved at all. There was distinctly more smell this time - last time was almost smell-free.
On cooling, I checked all the contacts from the chip (which was perfect, with no bridges at all) along the traces as drawn on the board. I removed the solder balls with the back of the knife blade again, and checked the resistance across all of the solder mount resistors from solder to solder. All was well. I had just one capacitor that had made good electrical connection but was not good mechanically, having far too little solder. I put the tiniest bit of paste on that end and used the soldering iron with chisel tip to make it good. I also used paste to solder the electrolytic capacitors in place, carefully positioning C11 as far away from the end of the chip as possible whilst leaving exposed solder at the other end of the capacitor to facilitate soldering.
I then ordered 2 more headers for the next board and the motherboard, and a replacement driver chip from Farnell.
I soldered in the stand-in giant resistors, and the through-hole components (with the nicked IDC header), and inspected and tested everything (that I could follow and understand).
JOY! This time, no drama, and the power LED lit up. Yes!
Now I have to wait for my next Farnell delivery before I can do the third board.
