Dead PSU?

I'm about to finish off my first Ormerod build and it's time to connect the PSU. One of the LED in the PCB is lit so something happens at least. Nothing on the Arduino board and nothing more happens. Yes, the jumper on the PCB is connected to the two left-most pins. Not even the PSU fan is running. I've used a multimeter with the PSU connectors and I can't get any reasonable values out from it at all. Even tried the old "hardrive power connectors" and it doesn't give anything reasonable on either 12V or 5V. Is the PSU really dead?

And yes of course, the button on the PSU is turned on.

I think one of the LEDs on the power PCB is for the +5VSB (stand-by) power, which is on even if the ATX PSU is in "off" state, and that might be the LED you have on.

Try disconnecting the PSU from the power PCB, and first measure if you have +5VSB (measure between purple and black, of course with the PSU connected and the switch turned on). Then, try to turn on the PSU by connecting PS_ON (green) and ground (black) with a paper clip or something. If that works, something is probably wrong (or incorrectly connected) on the power PCB. If it does not work, your PSU is possibly broken.

ATX connector pinout for reference.

With your instructions I was able to verify that the PSU is functioning.

This is what it looks like (PSU turned on):
[lh6.googleusercontent.com]

Is the power PCB broken?

Using a multimeter I can verify that there is 30 Ohm between left most jumper pin and the ATX pin corresponding to +5VSB and the middle jumper pin is connected to PS_ON. When I tried to manually turn on the PSU I connected PS_ON to GND. Not +5VSB. But maybe it shouldn't matter?

Edited 2 time(s). Last edit at 08/06/2014 02:30AM by bitfield.

if you look at the board as you have taken the photo
With the jumper removed
middle pin on the jumper is connected to pin16 of the atx conector and the
left pin on the jumper should be GND (pin 15 on the atx concector)

So with jumper in place you should have 0ohm between pin 15 and 16. If you do not you could try unplug the 24pin conector and leave the 4 pin conector pluged in and bridge pin 15 and 16 and the second led should light

Edited 1 time(s). Last edit at 08/06/2014 04:40AM by zeb00.

Thank you all. Truly a mystery. I removed the jumper, checked pin 15/16, no connection. Added the jumper and measured 0 Ohm. Added a paper clip between 15/16 manually, everything started up normally. Re-installed the PSU with the power PCB again and now it started. To me, there was no change at all. Anyway, there is power and I'm happy. For now

My guess would be pin 15 inside the atx conector on the psu was not pushed all the way into the connector and was not making contact with the board. But at least it works now

You are probably right.