Ok well the good news is, my 16 day hiatus is over, and I can try addressing my stepper driver board problem.
The bad news is, one of the two replacement boards that I purchased to address the two bad stepper boards is now bad too! I’m afraid to touch the last one.
I was grounding myself the whole time, so I don’t believe it was a static problem. I used a 15-watt soldering iron. I had the board grasped by the corner of the board, in a vice, and made sure it didn’t come into contact with any of the components or circuit lines. The page describing the necessary modifications is here.
First (before any modifications, and before apparently breaking one) I tested both replacement boards (unmodified) by connecting them (one at a time) via ribbon cable to the Y-axis port on my motherboard, which was connected to the computer. I connected one of the makerbot.com Kysan stepper motors (with the clip still on it, so the motor wiring was right), to the stepper driver controller board. I connected the molex 4-pin power connector from a PC power supply to the stepper driver board.
I turned it on (this worked for each of the two boards), saw not only the green power light but bright red and green lights next to the stepper motor connections. Those bright red lights will be on even if all you have connected is power and the motherboard connection, the stepper motor cables don’t need to be connected.
Here’s a picture I took later of what it looks like when it works, on an unmodified stepper driver board.. The ribbon cable is going to the motherboard, and on the left I’m holding the red and blue wire (red=12V, blue=gnd) coming from an ATX power supply’s yellow and black cables (multitester says it’s the right polarity and it’s 12V):
When the stepper motor is connected on a board that lights up like this, it can be controlled via the RepRap host software on the XYZ panel. I got motion from both boards before modifying the first of the two replacement boards (which is now not working).
I only made ONE modification, then immediately tested it, and it was already dead (the green power light goes on, but none of the lights near the stepper motor connector go on, and if you connect a stepper motor you can’t control it via RepRap host – it’s completely unresponsive). The only change I made was removing the 4-pin molex connector and soldering on a two-way screw connector in its place. Here is a picture of the first of the two replacement boards, apparently broken (note the green power light in the bottom right and its reflection on the RJ45 jack, which is the only lit LED).
I’m extremely irritated/concerned/disheartened.. When I modified the original three boards, one of those worked and two didn’t. Now one of my replacement boards doesn’t work already.
Has anyone else had this happen to them?
I’m open to suggestions. I’m afraid to modify the other replacement board, lest I destroy that one too. I’m seriously confused because I was extremely careful – maybe even 15watts is too hot? (I made sure not to use my 35watt soldering iron). I’ve checked the board and there are no obvious shorts etc.