i need help repairing my nintendo switch, it is drawing 0.00A on usb and ive tried a known full working battery from another switch with no luck.
there are shorts on the caps surrounding all 3 (from what ive read) buck regulators and also one of the capacitors next to the BQ chip. ive removed the BQ chip and the M92T36 chips but the shorts remain. i have no experience with BGA soldering and i need help pinpointing the faulty component.
Can you show which areas you think are shorted as well as the resistance to ground (in ohms) at these areas, as it’s likely they aren’t actually shorted
0A - possible fuse above USB is open, or could have been a bad M92 IC or bad soldering or diodes near USB have failed or the filter above is open
the fuse has continuity and the shorts on the caps are anywhere from .30 ohms to 0.00 ohms, i need to figure out how to get you a visual representation of the caps but they are the ones directly next to all of the pmic’s and the vertical one to the left of the BQ chip
Somewhat suggests that its a short on you SYS line… not sure how best to find out what, voltage injection maybe?
i do have a short on the SYS contact point but i dont know how to find it without removing BGA chips, how do i do voltage injection? i can buy a DC bench powere supply, ive been eyeballing one for a while and this would give me an excuse to get it lol
ive removed the pi3usb and all the of the PMICs and all of the shorts remain idk what to do next
Its a dead short, so it may be a case of plugging it in and seeing what gets hot. I had a board with a sys short, and plugging it in made the ic just below the soc warm up. It was a 30ohm short, so it was pretty subtle, but hopefully yours will get hotter and you may be able to notice it with your fingers or some ipa.
P13 isn’t on the SYS rail so that won’t help
Can you explain what you’ve removed? there is one main Max PMIC on the rear and two buck regulators SoC side which are on this rail.
After that you’ve got 8316 IC, backlight IC, AJZ IC, ENXX IC, DCO IC, list goes on - youll either wind up pulling everything and sods law will dictate it will be the very last IC you pull or just wait til you get a bench PSU else you’ll be spending the day reballing everything
i removed the big max pmic on the back of the board and the 2 little max buck regulators on the front, one is just under the emmc and the other one is just under the SoC shield.
i read somewhere that one of the filters under pi3usb could cause a 0.00a draw but they seem to all be functioning properly from what i can tell.=
as far as heat goes i have plugged it into my power bank and left it plugged in for a bit and felt all over the board and couldnt find anything even remotely warm to the touch.
if i pull the trigger on a DC power supply could you guide me on how to fault find with it?
is there a discord for this kind of stuff?
Sure, it’s just a case of connecting up the PSU to the shorted rail, limiting the voltage to <1v to start with and starting with a low cureent limit and increasing until you find the culprit.
Before you shell out for a PSU though, can you let me know the resistance to ground at the SYS rail, if you put your black probe on ground and the other one side of the 2R2 coil near the BQ IC and let me know the reading.
Its not just a power supply you will need though, you also need a way of checking the temperature. Sometimes ipa or freeze spray will be enough, but it could be that the Heat given off is quite subtle. In my case I used one of the tiny £35 thermal cams you can get off aliexpress and ebay. And the change in temp was from 25 to 30c, so I doubt I would have noticed it with anything else.
CPU buck by nature of board and trace layout gets a few degrees warmer, so likely your results were coincidental.
IMO thermal cams are a big waste of money particularly the sub $500 ones and are simply not needed if time is not of great concern, more often than not they lead to chasing red herrings down rabbit holes due false positives - For example it’s not uncommon for the large cap and inductor on the SYS rail to get warm in a short condition, even though the odds of the cap itself being short are near zero the thermal cam will flag it and make it appear that’s it’s faulty, there are more misleading examples than this though on the other rails.
Depending on the resistance of the short, a finger, your bottom lip, and IPA are all fine ways for identifying the culprit and in my experience more effective.
Just mentioning this so nobody wastes their money, not a dig at you Insomniac 
Nah I get it, relying on heat can be misleading certainly. In my case, I removed the buck that was warming, and the short did clear (on closer inspection there was a tiny crack I hadn’t noticed before). But yes, it would be perfectly possible for it to be the SOC and the buck was just warming a “normal” amount.
I just feel that the more info you have the better, but yeah, it’s easy to become reliant on something like that.
Classic, and worthwhile the OP taking note here and carefully inspecting all the ICs on this rail for any signs of damage as this is more common than the chips themselves spontaneously failing in cases of no liquid.
One thing I probably should have mentioned is, if your meters resistance mode has a high enough resolution you can quite often find the culprit which is causing a short to ground by simply placing one probe on ground and checking the ICs surrounding components on the same rail with the other probe, your lowest reading will indicate with high probability which IC/component is at fault.
For example, yesterday I had a short on 3V3PDR, I set my meter to resistance, I measure a 0.68 ohm short at the ENXX IC (on the corresponding nearby caps) I then do the same at the WIFI IC VIN (caps on this rail) and my reading is 0.85 ohms, etc, etc. I then measure at the large cap at the P13 on this rail and it measures 0.32 ohms which represent the lowest reading, pulled the cap, short cleared.
reistance to both sys test point and both sides of the coil are between 0.03 and 0.05 ohms
also do you happen to know what size solder balls are used for those PMIC chips? i would like to order some to try to reball and replace them if i can now that i know theyre not the fault. also are there balls on every pad or is there a pattern like there are on some chips? i cant seem to find any information online about either ball size or pattern
Just checking, you should be quite easily be able to identify the culprit with a bench PSU and/or meter as mentioned earlier.
I don’t tbh as I typically use solder paste, I would guess 0.2/0.3mm somwhere in that region. but leave them off for the time being until you’ve identified the real cause.
You can tell by looking at the underside of the IC, as far as I remember the PMIC and buck regulators are all a standard and full ball array, no fancy patterns here, pretty much all iphone stencils have these pitch/ball size.
ive been poking around the board with the battery connected with my multimeter in DC mode and i cant find voltages around the m92 chip or pi3 or the pmic’s for that matter but i also dont know where i should be poking and i am mainly just poking the capacitors and random pins and pads
Of course not, SYS rail is shorted and all other rails derive from that…
re-read previous posts, I cant help otherwise