So i had a switch lite in which the audio and STM MCU IC’s were bad. Removing both chips also removed the shorts on the passives around them, and it also turned a .48a braindead board into a now booting board. However, i don’t have speaker audio. When I plug headphones into the jack, i do get audio. I tried my best to get pics of all sides of the audio chip, im not the best with these types of components but afaict I have every pad connected to the chip and don’t have any bridges anywhere (even on the passives). I know the speakers in this shell are good as its my test unit, I am assuming it is related to shoddy work on my part but I am just not seeing it. Maybe some fresh eyes can spot something I’m missing, or if there is anything else I need to be probing to see if i have a break somewhere I’ll be happy to look.
The only thing i noticed before i had to walk away is diode readings for the caps attached to pin 23 of the chip seem really low (like .07 off the top of my head). Diode readings from a working board are much higher. Not sure if this has anything to do with it, figured it was worth noting.
xhttps://pdf1.alldatasheet.com/datasheet-pdf/view/1132327/REALTEK/ALC5640.html
i wasnt able to find the exact datasheet for this chip but from what I can tell, this one is good enough??
ok, had 5 minutes before bed to just take a couple more readings. Also, if anyone is wondering, I did go ahead and make sure the mute when headphones are disconnected option was set to false, restarted, powered down, both had no effect.
.08 diode readings on the two caps inline with pin 23, these same passives measure .394 across all of my other other boards
.8 V on the caps with USB plugged and no battery
1.8 V on the caps with USB plugged and battery connected.
I had a thought maybe I was missing the 1.8 rail on that line as according to the data sheet that provides power for a few things. I guess my next move would be to swap out those caps from one of my donor boards with the .394 diode reading and checking for changes, i don’t think they’re the issue but might as well remove as many variables as I can.
After that I’m kinda stumped as there does not seem to be much info floating around about the audio circuit.
slight update, still having the same issue but now i’ve noticed these two components are shorted as well as the leg on the chip. I tested the resistance of the 0401 and it was < 20 ohm while a working board was showing that same component > 100k. Working on what else is attached to this line right now as well as what exactly this pin is responsible for on the IC.
I really feel like I can solve this but man does my inexperience make this a chore lol
ok, so its related to power, also looks to be fed from pin 23? I am struggling to understand the description for DCVDD, do I want LDO1_EN pulled high, is that something I can test for?
I also did verify that both SPKRVDD pins are receiving 5v (just a touch under at 4.9) and that LDO1_IN is receiving 1.8v. So it does appear that all necessary power is being delivered to the chip.
wont let me go back and edit, double checked resistance on good board. I get around 24 kOhm on pin 42 and over 125 kOhm on pin 23 passives (it was ranging a lot but started to slow around these values).
Same pins on the broken audio board are coming back at 50 ohms or less, so something on this rail is faulty and I dont know what (yet…hopefully lol)
ok, last update before I have to walk away for the evening. From all my research on here, and all of my probing, I am like 95% sure the problem I have is a high short on the sys rail With black probe on ground and red on the right side of the LR2 coil above BQ, i see around 144 ohm. The passives around the MAX IC towards the center of the board seemed ok, I did notice a cap next to a small BGA with an EN marking on it that seemed a little suspect. Not really sure what this chip is, if its available to buy preballed, or if its even a problem. Most other common culprits seem to be ok, but when I get the time Ill take some photos and overlay my readings onto them for diagnosis.
any help in debugging this rail to track down the culprit would be great, feels like im inching slightly closer to the solution.
Just not gonna have much time during the week to play with this, but i did spend a bunch of time today here reading more SYS rail posts trying to figure this out. What i was able to do was remove the inductor on top of BQ. When i did this the left hand pad ranged from OL to jumping everywhere, the right hand pad stayed steady at around 85-89 ohms. Obviously the cap right below leading to the BQ chip also had the same reading. So I’m guessing here the problem is lying downstream (to the east) of this inductor?
The only other thing worth of note is, again, that weird EN chip to the east of the Max IC. The cap highlighted in red is the one giving me problems, the other caps and inductor all give me fairly normal readings from what I can tell. I removed this cap but it did not resolve it. Is this EN chip available preballed for me somewhere? I will spend some time searching here, but any shortcut or help would be appreciated. Normally I’d just remove and test but since its BGA I’m a little hesitant, would like to have a few preballed spares on hand before taking that dive as I’m not confident I’d be able to rebally properly as I have yet to do any of that type of that work, although I do have some equipment for it.
Getting a little closer, can almost feel it, if anyone has any ideas or suggestions I am listening. Thanks!
RP602Z330C-E2-F
Once again @Severence coming through with the help. Looks like I can order this chip, but according to his post this IC isn’t one prone to failure. I did notice some flaking on the side of it when I was checking out the balls on the bottom. Balls looked fine and I didnt notice any cracks or anything in the casing.
Have you ever questioned your intelligence? I have resolved the issue here and boy am I really embarrassed to admit it was all related to the audio chip. I just honestly couldn’t find any other fault with the board and decided I just needed to start pulling IC’s, but since I’m gunshy about BGA chips I decided I was going to start with where I first noticed the faults and pulled the ALC5639. Why the hell I didn’t do this to start, I couldn’t say, but lesson learned on this one. Soon as the chip was pulled all resistances came back into spec, plopped another chip from another donor board and the values remained the same.
So yeah, while I actually did learn so much about the SYS rail and a lot of other things I am so upset with myself that this wasn’t the first thing I did. So note to myself, and to other hobbyist idiots like me, remove the big variables from the equation first. I could have saved myself a weeks worth of headache and troubleshooting had i just assumed my work or the component was bad and pulled it for re-testing.
So, im an idiot, but I’m also an idiot with a completely functional switch lite that is ready to get buttoned up and sent of to the next owner.