I’m working on a Switch Lite where the seller wasn’t honest about the condition and it’s turned into a mystery for me.
It seems to charge with 15.3V and 0.09A drawing, but nothing else happens. No other signs of life. I replaced a shorted M92 and backlight IC and I don’t have much for shorts (no shorts around BQ chip either). There are only a handful of caps around the MAX chips that have shorts, so I’m not sure if one or both of those might need to be replaced as well.
The strangest part to me is that there’s an 8316 IC that’s getting extremely hot and there are no shorts that I can find anywhere near it.
Your basically saying what every beginner say’s here have a search of the forum as there is a lot of good info especially on the very things your talking about
“shorts” around the max IC’s you’ve highlighted probably aren’t shorts at all, check resistance instead.
regarding the 8316 IC, either the IC is bad (or support circuitry ie diodes etc) or your have a bent pin to the LCD connector most likely
Gotta start somewhere…definitely trying to learn and of course did searches before posting but couldn’t find anything as to how what appears to be normal “shorts” around the MAX chips could be related to the 8316 getting extremely hot.
I did check the LCD and touch screen connectors, but I’ll take a second closer look under the microscope. Thank you!
Then afaict it can only be an issue with the 8316 IC itself or support circuity as mentioned, I’d check there. Feel free to post images of that area if you want me to take a look.
I really appreciate the detailed reply. I’m really new to the investigating side of all of this. I have no problem with the soldering and removing/replacing ICs, but the searching out the problem is what I’m really eager to learn more about.
I’ll keep looking through the example searches you linked above, but do you have a preferred post or website that outlines how to properly check capacitor resistance (like preferred ground points, etc)?
I’m going to check resistance around the MAX chips and I’ll post some pics with my readings. I normally just use the USB port for my ground probe - should I be using a specific point?
Here are my resistance results for the big caps around MAX77812. I’ll check the other side’s MAX chip asap. The ones that read “5-18 k” were erratic while probing. There was no solid read, it just kept moving between that range cyclically.
I took a look at the board layers for the Lite and saw that it appears I should be seeing a different resistance from that of ground on that top-left capacitor for the MAX77812. As soon as I removed the MAX chip, I now get 68.4Ω on the left side and 0.3Ω on the right.
Does anyone think the MAX77812 could be what was causing the 8316 IC to heat up? Should I order both chips or would it be reasonable to think it’s just the 77812?
dodgy IC or someone messed with it prior / did a poor job reworking/reballing it
No, not ordinarily, this is for the CPU and GPU rails whereas the 8316 IC is for LCD rails. Might be a similar story to the other IC in that someone has messed with it prior and caused a short here too.
I cleaned and reballed the 77812 and the grounding issue came back. I’m going to order a replacement and hope that does the trick. I’ll be sure to update once the part comes in.
In rergard to the 8316 IC, you’ll wanna order one of them too and you’ll wanna check the two diodes in that vicinity also as if one of them is bad, your new 8316 IC will blow instantly on power on. They typically fail open afair
This sounds like a solid plan. I added the 8316 IC to my order, but I’ve never checked diodes before. Do you have a resource that shows what expected values around this part of the circuit are?
Also, check this out. I took a much closer look under the microscope and found two concerning things. The 8316 IC appears to be blown (chipped) and one of the components is sitting on the board at an angle. All pictured below.
Sorry I don’t, tbh if the IC is bad i usually just swap them out straight off the bat to be on the safe side. you’d typically want to measure diodes out of circuit so nothing else can influence the reading and you’d check it like you would any other diode using your meter, though be warned some meters might not have a high enough forward voltage in diode mode so you might have to use resistance instead. Also be careful as these particular diodes are the glass style package type and are very fragile (much like the IC too) . You can check them in circuit, measuring the resistance across them and then reverse your probes and do the same and post your readings, though as i say, other things could affect the readings in this case.
Worst case, you could always just order a few of the 8316 IC’s (handy to have extra on hand anyway), if the first replacement blows up / shorts out on first power on then you know for sure the diode/s are bad
Yeah, it’s toast, hard to say if it’s because it’s blown or if someone has been clumsy / dropped the board.
The diodes sitting on an angle isn’t so much of a concern and this is typical, just the way it settled during the reflow process at manufacture.
Alright, finally got the ICs delivered and installed the 8316 and the MAX77812. The short around the 77812 is gone and the 8316 is no longer getting hot, but I’ve still got a no-boot situation.
OEM charger is outputting 15.3V and 0.02A and the battery appears to be getting a trickle charge from this tiny draw.
I’m not sure if the battery is bad and causing the no-boot though. Battery read 3.596V before plugging in and 3.711V 30 minutes later. Do you think it could be too depleted to charge and/or boot? Thermal cam didn’t show any hot spots either.
I just checked the battery voltage again and to my surprise it’s dropping. The battery is now at 2.48V so there doesn’t appear to be any charging occurring. I’m not sure what to check next.
Connected to the board without the USB connected or with the battery disconnected from the board completely?
I’d probably charge the battery up manually on it’s own (not connected to the board) until it’s at full capacity / approx 4.2V . If the drain you mentioned was with the battery disconnected before then I’d monitor the disconnected battery voltage, if it drops in any meaningful way then it’d point to a faulty battery. If on the other hand the battery voltage is dropping considerably (following the charge I mentioned) when connected to the board then it’d be pointing more likely to a short on the board, so I’d check resistance to ground on your SYS rail first things first.
Also just to add, if the drain was when it was connected to the board, then possibly could be just standard draw on the battery and perhaps not an issue and maybe the problem is unrelated ie. charging issue / circuitry at fault
Hey have you figure it out? Im having issues im thinking its around the 8316 ic. I had pins missing from the lcd connector, put a new one on now im only getting a backlight. And did you order any extra 8316 i cant find them anywhere but china i can purchase a couple off you if you have any.
@Severence connected and disconnected. I took readings every 30 min connected and disconnected to see if there was a difference and there was, but it was small. The last reading I took was the surprisingly low one. I don’t have an adapter handy so I’m going to have to get creative to try to connect it to my bench power supply to manually charge it. Since leaving the battery unplugged it’s settled at ~2.8V.
Test measurements, OEM charger and no battery connected:
A: 15.2V
B: 15.2V
C: 4.2V
@rescalera No, not yet. I’m pursuing this in my very little free time. Trying to learn as much as possible. I’ll be sure to continue posting updates.
have a search of the forum as there is a lot of good info especially on the very things your talking about 
hopefully that solves the problem
Do you have a resource that shows what expected values around this part of the circuit are?
