Back.. But now ANOTHER stepper board is fried??


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 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.


8 Responses to “Back.. But now ANOTHER stepper board is fried??”

  1. James Glanville says:

    Very odd, it almost certainly isn’t the soldering iron – unless the pads are lifting up, there are no components to destroy there. Could you have disconnected the motors with the board powered up? This tends to break them, just wondering if that’s the problem?

  2. nophead says:

    The obvious difference between the two photos is that you did not have the motor connected in the first shot. Do the LEDs light up when it is not connected?

    Are you sure the enable line is in the right state.

  3. Renoir says:

    Hmm. I’d think it’s unlikely to be anything to do with the soldering itself – there are no nearby components and the power supply plug is not sensitive.

    I’ve built a few of these boards from scratch, with minimal skills, and managed OK – so they’re not terribly sensitive to static.

    The biggest problem I had was testing – there is a single ‘enable’ line from the control socket (pin 5 on the ribbon cable socket) to the arduino/controller board, and if that is not ‘high’ then there will be no lights and the board appears ‘dead’ except for the power light.

    Interesting – checking the specs, for stepper drivers version 2.2 pin 5 (enable) is high for on, low for off.
    For stepper drivers version 2.3 pin 5 (enable) is LOW for on and HIGH for off. This ought to be a configuration option somewhere in the firmware/settings.

    My guess would be to check and re-check the testing setup. Leave stepper motors unconnected (rely on the lights) and run a test with your working board. (flashing lights). Turn all power off, unplug your working board, and plug in a ‘broken’ board – using exactly the same setup – same wires, same connectors, same position on the bench, etc. and run the same test. (in scientific terms, you change one variable while holding everything else exactly the same). Repeat for all stepper boards, even the ones you thought were broken before.

    This will tell you whether your assumption (the board is broken) is right, or whether it’s a more subtle bug somewhere else (like a broken ‘enable’line on one ribbon connector, or a single broken output on the main reprap board. I can’t tell you how much time I’ve wasted looking to fix a problem in the wrong place… :-)

  4. Brad says:

    I have the same problem with one of my boards.
    Now I modified the replacement board and only one pair of leds work, ie the motor can only go in one direction.

  5. jkeegan says:


    Ok, first, apologies for not replying earlier. I’ve had no time to work on the RepRap until now (but I did read all of your comments).

    Just now I desoldered the screw terminal I’d connected and tried running 12V and GND wires directly to the power pads (making sure they went through the holes and presumably made contact on both the top and bottom of the board). THAT worked! So my soldering of the screw terminals must have made no connection on the top of the board maybe? Not sure.

    By “worked”, I mean that when the board was connected to a powered motherboard via ribbon cable AND had the 12V and GND connected from the power supply, I’d not only see the green power LED but also LEDs near the ABCD motor connector light up. (no motor connected). Previously, I’d have only the green power LED light up.

    More later. Thanks for the words of encouragement everyone!

  6. nuttzy says:

    Problem solved!…. kinda….. maybe….

    Keep plugging away!

  7. i use those copper tipped soldering iron but after a month or two, my soldering iron tip would just break ‘

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