PGA2350 dead on arrival, Any Tips?

Discussion
1

I am using a PGA2350 in a prototype PCB stack in a project. Each gadget has four of these PCBs. I’ve been happily running gadget #1 for some time now, and just built #2. In the process, I have exhausted my supply of PGS2350s (more on the way). I have one board out of four that I just built which seems dead. It is a brand new PCB and PGA2350 module. It “fails” upon connection of the USB cable to the host PC. I can see +5V going into the MCU module, but the reset and boot pins are stuck low. It is not the switches, I checked that circuitry. The other boards behave as expected, with those pins being pulled up.

One other clue, one working board I spot-checked I observed +3.3V on the appropriate output pin. I am not using that output, and on my design the 3V3 output and enable pin are floating. But on the bad board, there is no 3.3V on the output pin. I’m not sure that’s bad, since I haven’t set enable one way or another.

I also did a thorough visual inspection of the board, nothing unusual found. Initially thinking it was the USB connector, I removed, cleaned, and reinstalled that. No joy.

While I wait for new PGA modules to arrive, any ideas of what I could have done wrong to make this appear bad? I’d love to learn that I did something silly rather than being so unlucky to have one bad MCU module.

-Chris

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It would be best to reach out to our support team (Contact Us for Raspberry Pi Technical Support - Pimoroni), and provide pictures of your setup to see if they can spot anything

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Not sure that would be helpful. I’ve been over the whole assembly with a stereoscope looking for faults. My question was more asking for any ideas about how a PGA2350 might fail in such a way that with +5V input there is apparently no 3.3V being generated, and for certain the Boot and Run pins are not being pulled up.

Anyway after more testing this morning, I’ve concluded that the +3.3V output pin is shorted to ground. Hard shorted. It doesn’t go anywhere on my board, and there are no visible issues on the module or PCB. It might be on the underside, and I will check that when I replace the part. It’s likely I got a stray solder ball got lodged into someplace it shouldn’t.

-Chris