This is a very unusual chip to blow like this. Just like with the blown driver chip, damage like this indicates a LOT of power. But this chip is nowhere near any high voltages.

The Diagnosis

  1. Assembly error? Nope. This was an assembled PRO board, so it was fully tested prior to shipment.
  2. The board had two stepper motors connected and power added. The motor current was set and the motors locked. Good.
  3. When the board was connected to the PC, the chip blew.
  4. Primary suspect #1 – some issue with the power supply, perhaps some voltage to the chassis causing a lot of current through ground. Supply was a cheap 36V 10A Chinese switching supply, that measured 36 volts between the chassis and the V-. This seemed odd to me, I’d prefer the V+ and V- outputs to be isolated from the chassis.
    Side Note: You can see a cheap Chinese vs. quality power supply here: It’s 15 minutes and worth the watch.
  5. What about the cable from the HobbyCNC PRO to the PC?

    a. The customer did not purchase the parallel cable from me.
    b. Turns out the customer purchased a serial printer cable. Only half correct. The PRO requires a parallel printer cable, all 25 pins, wired straight-through.

So, I’m not 100% certain is wasn’t the power supply, but at this point, my money is on the use of the serial printer cable.