rurwin wrote:You definitely have a problem with the USB lead. I suggest you go out and buy a phone charger cable from a phone shop. What you have is probably only designed for data and it may cause you problems in the future even with your working board.
It is very possible that your two boards are differently sensitive to the reduced voltage. But that doesn't explain your problem, given that it still fails with power supplied to the GPIO pins and 5.07V between TP1 and TP2. It sounds to me like it is a faulty RaspPi.
Have you tried using the SD card from your working board in your non-working board? That would be the only remaining test that I can think of. There's other tests that I could do, such as monitoring the network traffic and watching the DHCP packets, but that is not something to be done by someone who doesn't understand networking protocols. Anyway if two identical boards behave differently with identical software then they are not identical boards -- one of them is broken. So if swapping the SD cards doesn't get you working then I think you should return the board as faulty.
I'm inclined to agree that it's a board problem. I am au-fait with packet monitoring, but to be frank, I haven't bothered. I can guess that the traffic will show either incomplete outgoing packets, or ignored replies. Either way, it doesn't take me any further down the road to a diagnosis - I know that the problem doesn't lie in the connection between the patch cable, my network and my DHCP server since it works with all other devices.
I take your point about data vs charger, and will probably give it a go anyway, but given the results with power on the GPIO pins directly, with no voltage drop under load, it's unlikey to alter the result.
I have tried the SD card from my working board in the non-working one early on in the test process; I must have forgotten to mention it. Same result - no connection.
