12V power problem


 
J

Joseph D

New member
Hi all:

I've recently purchased a 4.2.4 (rpi B) from the store. I have everything assembled and am waiting on a case I ordered. I can power up the rpi via its micro-USB, and everything seems fine. But if I instead use the 12V power on the HM, neither the LCD nor the linkmeter web interface comes up.

With the 12V supply plugged in, I checked a few voltages on the board using Byran's troubleshooting "map." I see 12V where I'm supposed to, but the 5V sites are only getting around 1V. I assume I've got a bad solder, or possibly a short, somewhere. Any tips on where I should start looking?

Thanks!
 
The little 3-pin "OKI" board is what makes the 5V from the 12V, so you should start looking there. And also verify that you have installed the 3.3v regulator in the proper spot (the transistor between the button and the ATMega), I've seen people end up with a BS170 there instead of a regulator by mistake...
...but most likely a short anywhere on the 5V line could be dragging your voltage down. Perhaps post pics of your board and someone might be able to spot your issue. Could be a backward electrolytic, solder bridge at the CAT5 jack or elsewhere, easier to diagnose with pics.
 
If running at 5V from the USB power makes the HM work, then I would assume that the 3V3 regulator is installed correctly.

I recently had two "OKI" boards (new, form Mouser) with dry soldered header pins, causing the same issues that Joseph has. After cleaning and reflowing the solder joints all worked fine.
 
Peter F said:
I recently had two "OKI" boards (new, form Mouser) with dry soldered header pins, causing the same issues that Joseph has. After cleaning and reflowing the solder joints all worked fine.
Click to expand...

Bingo. Reflowed the solder on that part, and it works like a charm. Thanks a million!
 
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