Troubleshoot Power Comms 1.3 Board

I finished soldering the parts onto my powercomms board. Let me start by saying that I am not a newbie to electronics so I am confident that the components are soldered correctly.

I attempted to convert a classic ATX power supply using the instructions on this site and I plugged the powercomm to the supply. Immediately I saw a small spark near the power connection and heard a small pop. The power supply was dead and I assumed that was all that died.

I happen to own a variable dc power supply so I cut the connector off the ATX supply and set my power supply to 5v and connected the red and black wires up. So the two middle pins are ground and the red pin is +5v and the yellow has nothing on it. My assumption is that the 12v yellow is not used. Is this correct?

The powercomm does not power up. Not LEDs are lit and I don't have +5v at pins 15 and 16 on U2 like the instructions say. I'm wondering if I fried the voltage regulator.

Any suggestions on troubleshooting this one?

I hate when I do that. I ask a question and then moments latter take a risk and fiqure out the answer.

I disconnected the +5 and wired it up as +12v using the yellow wire. This caused the LED to illuminate and there is +5v at pins 15 and 16 of U2.

So now my question is...Is the red wire(+5v) needed? In other words do I need both the +5 and +12v for the board to operate correctly or is only the +12v needed?

No only +12V is required.

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[www.hydraraptor.blogspot.com]

Just the 12V should be OK. I'm using a 12V-only supply from an old project I dismantled.

See I agree, I'd be using 5V as my standard for the boards, least thats how I do it for all the RepRap boards I've designed, although these are mainly for the Arduino trunk.

Most or all of the RepRap boards have an onboard 12v -> 5v regulator. Its one of those quirky things Adrian has prodded us to do. The reasoning behind it is that you could theoretically run an entire RepRap off a 12v car battery for example.

Ah, quirky, yes. But also very useful in developing countries. I was reading about the MultiMachine from the links pages and they do a lot of similar stuff like wiring car batteries together to weld. Pointless for us but crucial to others. I like it.

Demented