Pi 0 wifi hack postmortem

[razner]

I attempted to modify my Pi zero with "built in" wifi by dismantling a wifi dongle and soldering it to the test pads on the underside. The PI heated up and died, however. I don't understand why this happened, I think I had the connections correct, and it actually turned out basically identical to this:
http://hackaday.com/2015/11/28/first-ra ... back-wifi/
I was powering and connecting to the pi with a USB to TTL serial cable, perhaps that could have something to do with it?

Here is a picture of my mod:


I'm not sure, maybe I just had shorted something elsewhere? I'm not familiar with what the failure cases on the pi are.
I think this would be a useful mod still, but I don't want to try it on my other pi without understanding what happened first.
If I where to try it again is there some junction on the pi that I could monitor with a multimeter to get an early warning that something is wrong?
Anyway thanks for any help in advance.

[Heater]

Clearly you connected something wrong or accidentally shorted something.

Early warning is a bit tricky. By the time you have applied enough power to make the thing work it's also enough power to kill it.

Never mind "failure modes" of the Pi. When you are hacking something like that it is pretty certain that the failure mode is whatever you have done to it. Only you can know.

Fine wires and careful soldering are the order of the day.

Check your connections. When it's done use a multimeter to check that everything that should be connected is and nothing is connected that should not be.

Then...

Check it all again.

Then go back and check you had the right circuit diagram in the first place.

[gregeric]

Did you take care to place insulation between the dongle & Pi PCB's? It appears to be resting across a couple of GPIO plated through holes. I'd also look at potential shorts around those GPIO pins you've previously soldered. And look for random solder splashes.

Shorts & dead Pi aside, the module will perform better with its antenna hanging off the edge of the Zero, not in the middle of the Zero's ground plane as you have currently arranged it. The hackaday example did that, but was careful to insulate the exposed contacts on the back of the Zero.

[razner]

Yes that's all good advice. The circuit for the hack is simple enough so I am sure I shorted something.
Also, I didn't disclose that there was another "hack" already on the board, which was the board from a usb to ttl cable wired between the gpio and a micro usb breakout board. I can't say that it was done very cleanly so that would have increased the likelihood of a short by a good deal. I tend do do things overly quickly but If I try it again I agree it is a good idea to be better outfitted with thin solid wire and solder wick and do more double-checking.
tThanks

[edge0f17]

Is it really dead? Can you desolder pp1 and try powering it over usb?

My guess would be that the pp1 and pp6 wires are both touching the usb mountpoints.