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September 21, 2013 at 12:58 pm #22644
Received my OSPi from OpenLab a couple of weeks ago. I got time to open it up this weekend, but when I tested with a 24v AC power supply I get no green LED. There’s nothing measurable at the 24v and 5v points on the board. Anything I can try? The board looks clean, no breaks or visibly damaged components. It’s the 1.2 version.
cheers, Pete.September 22, 2013 at 9:02 am #25561
Sorry to hear that. Here are my suggestions:
– Use a multimeter to measure the resistance between +5V and GND (there are multiple +5V pins, any of them is fine). It should be around 4.4 to 4.7 kilo-ohms. Also measure VCC to GND resistance, should be around 100 kilo-ohms. If not, it seems there is a damage somewhere on the board.
– If the resistances are correct, the problem is more likely with your 24VAC transformer, or the connection. You can use the multimeter to measure the *AC* voltage of the two wires of the transformer. Then make sure the wires are plugged into the screw terminal with good contact, and that you’ve plugged it into the ACIN port, not the COM port.
Let me know your findings. If the board is damaged or DOA, you can contact OpenLab for a replacement.September 23, 2013 at 4:32 am #25562
Thanks for the quick reply. Test results are:
Resistance 5v to GND: 1.1M ohm
VCC to GND: 105 K ohm
The 24VAC psu I have shows 27.6 unloaded and 26.1 while holding a sprinkler valve open.September 25, 2013 at 12:50 am #25563
The 1.1M ohm 5V-Gnd resistance is a problem. That most likely means one of five pins of the LM2596 switching regulator is not connected. You can take a look at those five pins under good lighting condition to see if any of them seems to be disconnected from the PCB pad. You can try to apply some solder to reinforce the connection if that’s the case. At any rate, this is an unusual case as all OSPi boards are fully tested. Again, if the problem cannot be solved, you can contact OpenLab for a replacement. Alternatively we can send you a replacement board directly, which will take 2-3 weeks to arrive.September 26, 2013 at 10:58 pm #25564
I checked the connections on the LM2596, and re-soldered just in case, but no change. I’ve contacted OpenLab, and they’ve said they will sort something out. Many thanks for your help.
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