Arty A7-35T: Suddenly no power on

[Tony Nguyen]

Hi, 

I have an Arty A7-35T that I bought last year but never really used. I pull it out of the cabinet today and use for the my next project. However, when I plug the usb to it, no LED on at all including the power LED. I also see neither overheat or anything concerning. I measure the VCC and GND (labeled in the connector) and read out 0V. I unplug the device and see that the external power jack and short circuit (all three pins) are shorted, though I never used the external source. Again, no visible smoke or overheat on any chips are found. 

I bought it roughly a year ago (potentially less than a year), I never tested the board when I received it. It was meant for one project that was never started, so I just sit in my cabinet. Could someone advise what the debugging process should be? 

Thanks,

Tony Nguyen

[JColvin]

Hi @Tony Nguyen,

I'm guessing you have a Rev E of the Arty A7 35T (the Rev C version had a jumper where you would deliberately select between USB or external power, so if you had the regulator option selected, nothing would happen if you only plugged in the USB).

How did you determine the three pins on the power barrel jack are shorted? If there is no power supply applied, the voltage difference between the three pins will all be 0 V; if you instead measured the resistance between the three pairs of pins and got 0 Ohms between all pairs, then they would all be shorted (though I would be very surprised if this was the case).
Regardless, it's still not a good indicator that when the USB is connected that there is no voltage difference between the VCC and GND pins on a Pmod port, nor have the power good LED (LD11) not turn on as both of those are dependent on the 3.3 V rail which is derived and enabled by the 5 V rail (which is derived from either the USB or the external power supply).

We could do some additional debugging to find out where the root cause is, though realistically either one of the power switch ICs failed or the regulator (though I'm happy to continue debugging if you wish). But as you have not used the device in a way that I would consider "out of spec", I would imagine the board is suffering from a manufacturing defect and that you should pursue an RMA.

If you purchased the board from Digilent directly, please fill out the Sales and Order Support form available on the Digilent website here: https://digilent.com/shop/shipping-returns/#return-policy, making sure to provide the serial number and that you worked with me here on the Forum.
If the board was instead purchased from a distributor, such as Newark or RS Components, you will need to contact the distributor to find out their RMA process (the distributor would then work with Digilent for their own RMA).

Thanks,
JColvin