Yeah, I’m getting 3.3V on the two caps that previously read 4.36V and 0.0V now with the side board connected.
try to check back to next nearest component then IC where applicable, not just TP’s
nah, check continuity if your not sure, they’re one and the same rail 
yep, or at the flex connector
Can you get me a close look at the fuel gauge too as from a distance I’m not keen on the look of it, on edges too if you can
Alrighty, checked continuity and found it goes over to these two points:
I’m getting 3V at both of the points in the photo.
Here’s a close up on the fuel gauge:
Previous image of fuel gauge area looks different, was it of a different board? if no on edge/s too if you can
No, I only have this one Switch Lite board currently so all pics are from it. Some pics are taken from the microscope and some are from my phone. The last two are from my phone. The colors are odd and the lighting is bad on the microscope photos - it looks much better in person. When I take pictures through the microscope’s OSD they’re overly compressed and the detail gets washed out. ¯_(ツ)_/¯
I’ll take a few more pictures of the fuel gauge from different angles.
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Ah, got busy with work and then got sick - sorry for the delay. Here are some pics from various angles of the fuel gauge.
Hard to tell, but in the last image it looks possible the corner has a chip in it, possibly into the ICs die or maybe it’s superficial and just the top coating (though does seem like someone has been monkeying around in either case). You can probably tell better yourself in person.
I’d replace it as a matter of course anyway given the symptoms and how cheap you can pick up these ICs, and I’d get them from Mouser, Digikey etc to avoid any potential issues which could muddy the water
Alright, I just replaced the 17050 with a known good from another switch I have for parts and the behavior is exactly the same. I’m really lost on this one.
I decided to reflow the MAX77620H and 77812 and…the dang thing booted. I might need to reball and try again on the fuel gauge though since it doesn’t appear to be charging correctly. The screen shows the charging icon, battery at 35%, but it’s only pulling 0.02A.
Dropped 2%, plugged in, while I was writing the above. Here’s where it gets weird. I shut it down from the power off menu and then it started pulling .57A and charging the battery…
Checked it at 1 hour and it is indeed charging (got to 87%) while powered off. As soon as I booted the Switch it went down to 0.02A again. Something still needs attention, but I’m not sure what. Would that be the fuel gauge causing it not to charge when booted?
Decided to use my limited free time to rule out the old and new fuel gauges. Reballed and reinstalled the original and it would not charge while powered on or off. Reballed and reinstalled the known good replacement and it will charge when powered off, but not while powered on. So, the 17050 did appear to need to be replaced after all, but a charging issue remains.
Are you exlusively using the nintendo ac adapter during this or regular 5V supply, or a mixture of the two?
Might also be worthwhile measuring resistance to ground on the rails mentioned previous (black probe on ground) just incase you have a soft short causing excesive draw, given rapid drain / low current charge when booted to OS
Yes, exclusively the OEM charger. I’ll use the 5V charger and report back any findings.
We’ve covered a lot over the last month…forgive me…I should measure the resistance to ground on the 3V rails we most recently discussed?
5V adapter charges at 5V 0.03A. It does the same thing as the OEM charger though, with the device powered off, I plug it in and it goes 5V (15V for OEM) and starts at about 0.47A and then about as soon as the display turns on it drops to 0.03A.
Spamming again, sorry. I just noticed that it will charge in Sleep Mode on the 5V charger. So, out of curiosity I swapped back over to the OEM and put it to sleep and it was still back at 0.03A and then I unlocked it and…it started charging at 0.35A while on. So confusing.
Haha 
no worries, all primary rails surrounding the main max PMIC (check at those large inductors from your image, SYS, 3V3PDR.
Not, sure, 0.4A/0.5A is typical trickle charge prior to boosting. The fact it’s dropping back down to virtually nothing on power on / coming out of sleep suggests either a short on an active rail / fault on said rail / line or it could and might typically be more generic issues such as dodgy USB connection (enough to sustain high current etc or or OL etc) or M92 related issues . Did you verify continuty (and verify resistance in while doing so) to actual IC destinations from the USBC breakout board?
Just guessing but I think your primary issue was fuel gauge initially, as it tracks with your symptoms, I doubt reflowing PMIC or CPU/GPU reg resolved anything and is purely coincidental (though CPU/GPU reg could independently cause such issues but based on everything else I’m doubting) so perhaps your battery was so low, fuel gauge was bad, and it just turned out it booted / displayed charge indicator after it exceeded min voltage. Randomly reflowing stuff rearely ever does anything other than muddy waters (like in this case 
as now were suspecting them for no real reason)
If it were me, I’d probably swap fuel gauge out with a new one regardless (I recognize you’ve got one from your known good but i’d still do it incase it’s now sustained damage) and following verifying USB I’d change M92, if still no change then BQ, then only after that I’d start looking into more serious culprits, just because they’re easy to do
Alrighty, here are some findings:
-usb breakout continuity verified to destinations (I couldn’t find a known-good resistance list though)
-I don’t have any more 17050’s on hand so I’m placing an order
-I had an extra M92 and BQ and swapped one at a time and the behavior persisted
The more I look at the charging/power circuit I’m curious if the fuel gauge is really what’s at fault here. I just don’t know how it interacts with the BQ while in a booted state. I can charge when powered off, and when booted, I can charge as soon as the Switch goes into sleep once while connected to USB. That kicks it off and it maintains that charging status until the battery is full. If I unplug/plug in again I have to put it to sleep to start the charging again (and can unlock and use it after that and maintain a charging status).
Well it’s just what you’d expect to see if you to measure a copper wire + whatever your leads resistance is. Of course, if you have a filter inline (at the P13 IC for example) then it could increase resistance marginally. If you measured a line at 5 ohm or 10 ohm (or more) then you can pretty definatively say somethings wrong.
As far as I remember i don’t think it directly interacts with the BQ IC. The fuel gauge keeps track of battery capacity by monitoring current (large current sense resistor right next to it) , been a while since i looked at the datasheet but I also think it monitors battery temp too and a few other things, it might be worthwhile you reading the datasheet .
Next time you pull the fuel gauge to replace it might be worthwhile just verifying all relevant lines are going where they should (and looking at resistance like mentioned earlier too) to ensure nothing is open or partially open. (I recognize this is of a regular rev switch board but you should be able to corelate the pinout / cross compare with the lite boardviews)
Just to add regarding fuel guage,
If the fuel gauge were bad / not coimmunicating with the SoC you’d either get no boot black screen scenario, or a BSOD or incorrectly reported battery capacity or temp status, all of which could cause issues with high current charging being enabled amongst other things. That is in a usual scenario mind, not saying fuel gauge is definatively your issue here.
Does the battery capacity percentage shown on sreen hold or does it rapidly decrease? if it does then it’s either a short on a rail or fuel gauge related fault (or lines relating)
Hello and good morning. I let the Switch sit in a powered off (not sleep/standby) state over the weekend and was surprised to see the battery did drop from the somewhere in the 90% range down to 68% when I powered it on today. Not sure what would cause a drop like that when powered off and not in use but I’m also not sure if that’s normal - never really stopped to check that on another switch before.
The battery capacity percentage does display and hold without rapidly decreasing. In fact, on Friday I played a round of Mario Kart just to make sure everything else was working normally and aside from this strange “only charging after sleep” issue everything else works great.