Phat dac trouble shooting individual pins on a pi zero


#1

For reasons I can’t seem to remember myself, - I believe it was to remove some of the height of the hat - I took it upon myself to unsolder my phat dac and in doing so, I think i removed more than I should have. In fact, I am pretty certain I removed the entire solder pad on pin #20, and by the time I was finished, a few pinholes looked damaged. Undeterred, I carried on, and now have the phat dac sitting nicely on the pi zero using only one male header. Appearance wise - a success.
But of course I have no sound now. probably due to at least one aforementioned damaged pin.
Is there any command line function to test which pins on the pi zero are not functioning properly? I tried aplay -l and the soundcard is appearing, lsmod looks ok, but before I attempt any physical fixes, I was hoping I could narrow down the issue to a certain number of pins.


#2

You can see the absolutely essential pins marked here: https://pinout.xyz/pinout/phat_dac

Since pHAT DAC is write-only, it’ll always show up on the Pi as if it’s working fine, even if it’s not plugged in at all. This doesn’t help with diagnosis unfortunately :(

It might be worth trying the following, to see if you get sound:

sudo systemctl stop pulseaudio
speaker-test -c 2 -t wav -D hw:0,0

#3

Thank You for the tip and advice. Sadly, I have demoted myself from a DIY’er to a FIUM’er as I believe I now have a new case for my pi zero - being a non working phat dac soldered firmly onto the zero. Somehow, the pi still works well.
I took a stab at dmesg, found a few interesting tid bits there, carefully ran fsck and nothing seemed to assist. I even re-imaged thinking i could start with a clean slate. aplay-l finds the soundcard with no issue, and both the asound.conf file and the boot/config.txt file appear in order. In fact, everything appears to work as it should, even the speaker test runs with the exception of sound.
As they say, if it aint’ broke - don’t fix it. I will use the headers from now on, and that promise is good for the next week or so.
On the bright side, now I get to buy another!


#4

Might be worth posting a picture of the soldering to see if we can spot any pins that could potentially be repaired.


#5

That’s a good idea. Pls take a look near the voltage areas where some board has been scraped and let me know your thoughts. Also I couldn’t get solder to flow where a pad was missing so pins 21 -23 in the opposite corner look iffy. The side shot shows my attempt to use the underside of the board where a pad may exist. There are a few globs where I thought more solder couldn’t hurt. Soon I will have 40 Hershey kisses a sitting on the DAC. The not working note is so I don’t confuse it with my other similar DAC that works great like this.


#6

I’d wager the +5v power trace is stymied since it runs around and over the top of the 3.3v pin which is in bad shape too.

If you’re feeling adventurous, you might have some success jumping a thin wire (maybe a piece of jumper jerky with the ends ripped off for flexibility) from one of the +5v pins right over to the top middle lead of the onboard 3.3v regulator.

The regulator is the chip with 3 leads, two on one side, one on the other, that’s to the right of the C in DAC and located top-left of the DAC chip itself. The single lead on one side is the +5v input with the 3.3v output being diagonally opposite on the right-hand side.

This could be a long shot, since some of the smaller data traces could be damaged, but worth a try if you have a spare moment!