I managed to buy another broken ebay switch. I am still new to fixing Nintendo switches and yet have to learn a lot of stuff about it. Now I encounter one that draws 0.05A with battery plugged in and won’t charge nor power on. The usb-c pins looked good and measurement in diode mode was ok for the outer pins. Further on I tested for shorted caps and I found that one small cap below M92 was shorted as well as one vertical cap to the left of BQ IC. My question now before I try and take off BQ:
Can a faulty BQ IC cause a short on a cap below m92, see pictures for reference?
I’ve seen from TheCod3r and Jason’s Electronics repair videos that a shorted cap below m92 usually indicates a dead cpu.
Sorry, I can’t post images yet and thx in advance for any tips!
It would appear you have a short on your SYS rail, this is typically as a result of the BQ IC, and it’s entirely possible this short has cause a subsequent short on your 1V8PDR (cap below M92 IC)
Remove the BQ IC and see if the short on the cap near the large inductor clears, if so, then proceed to check your 1V8PDR, if the short remains then remove the M92 IC as @Integ209 suggested.
Completely wrong, don’t always believe what you see, literally everything on the board connects to this rail in some way and the SoC stands as much chance of being faulty as any other IC on this rail, this is a typical cop out statement from somebody who doesn’t know what they’re talking about.
Thank you for your input, really appreciate. I guess I won’t give up on this one yet
Here is what I did in the meantime:
I measured the USB C pins using a breakout board (battery plugged off), the values on the outer and inner pins seemed ok, no major differences to the working ones. I think the USB port is fine.
So next I managed to pull of BQ and the short on the big cap to the left of BQ as well as the short on the cap below M92 still remained. Unfortunately my cheap hot air station broke and I ordered a new one (Atten 862-D). Should arrive on Tuesday at least.
I will pull off M92 next and see what happens, at least I want to get the board to draw more than 0.05 A with battery plugged in.
What does the Sys-Rail do? What values should I expect on this rail on a working one? Are there any schematics that I can refer to in order to learn a bit more ?
Will keep you updated and thanks for your help! (Sorry if my messages are confusing, English is not my native language)
Ok, so what I’d do is measure the resistance to ground on your other primary rails, these can be found at the inductors surrounding the main Max PMIC, see this topic for more details.
Can you also let me know specifically what the resistance to ground is on the SYS rail? (on the cap near BQ)
The SYS rail is effectively regulated battery voltage, there are many ICs on the board which use this rail as VIN. You would expect it to measure approx 4V, but at this point in time, you shouldn’t be connecting battery or USB to the console with potential shorts elswhere.
Resistance to ground on the SYS rail would normally be approx 7K or greater.
Typically (but not always) if the short on the SYS rail is not as a result of the BQ IC then it’s usually one of the two Max ICs below and to the left of the SoC, but before going down this path I need detailed resistance readings of the other previously mentioned rails as it’s whichever rail represents the lowest reading (if there are others which have a short to ground) that determines next actions… for example the SYS rail might not actually be the primary fault etc.
Also, I should have mentioned this earlier, but can you also disconnect the EMMC module from the mainboard and check if your 1V8PDR short clears, sometimes the EMMC can fail causing this, chances are it’s not the issue in this case but it’s worth checking.
@Severence Ok, so what I’d do is measure the resistance to ground on your other primary rails, these can be found at the inductors surrounding the main Max PMIC, see this topic for more details.
Besides the cap marked with a blue circle, I can’t measure the resticance to ground on the other caps around Max PMIC. I measured 60 Ohm for the cap (blue) on the cap near Max PMIC. Am I measuring something wrong here or what do you mean by measuring the inductors?
@Severence Also, I should have mentioned this earlier, but can you also disconnect the EMMC module from the mainboard and check if your 1V8PDR short clears, sometimes the EMMC can fail causing this, chances are it’s not the issue in this case but it’s worth checking.
Unfortunately that did not solve the problem, the short on 1V8PDR remains.
Please note that I am not experienced in soldering, so my BQ soldering attempt may be sub-optimal. I identified several shorts on the bigger caps behind the CPU as well as around the PMIC. Also I still haven’t removed M92 IC, should I try this one and see if the short on 1V8PDR clears?
Sorry man your losing me on this one a bit, as you said the short had remained after pulling the BQ IC right? 200K is not a short and would be fine on SYS - particularly with the BQ IC removed… but, is your meter manual ranging by any chance?
Also it’s a bit concerning to me that some of those caps below SoC have slid around, which typically indicates poor prior rework, perhaps somebody has attempted an SoC reflow prior to you? in which case I wouldn’t have too high hopes for this one
I’ll come back to this after clearing up the above
I think I wasn’t clear on this one. I put the BQ IC back in because I was already giving up on this one. The short remained even after pulling out BQ. I can’t see any clear reading on the shorted cap near BQ. I am using the following mode (200kOhm) on my Multimeter
Ah, this is the likely reason for the 200K reading, though the meter should still give a zero reading (if the line is short to ground), no idea why your meter shows a 200K reading if it’s supposedly below the limit.
This time put your black probe on ground and red probe at the points of interest, Set your meter to the 20K position and measure that same [SYS] cap again and lemme know the reading, if it comes back as “20K” on the meter display then change the range to 2K if the reading comes back as “2K” then change the range to 200 and let me know the reading, if the rail is shorted you will get a real reading on the 200 ohm scale.
Yeah it’s too low, so next port of call is finding out if you have a short to ground on any of your other primary rails and if so which one represents to the lowest resistance measurment, we’re doing this to narrow down the potential culprit.
Here’s the points I was reffering to earlier, you put your black probe on ground and your red probe at one of the highlighted coloured points, each of these points represents a different rail.
You would now be looking at ICs which have a direct connection to both the SYS rail and 1V8PDR, the main PMIC (Max 77620 ) is connected to both these rails, so it would be a valid candidate as the culprit in this case, but there are another couple of ICs which also connect to both these rails, the two MAX77621 (CPU/GPU regs below and to the left of the SoC) and I would probably start by pulling these first and seeing if the short clears prior to the main PMIC but that’s just my personal preference.
The hope is your SYS rails hasn’t shorted with your 1V8PDR and if it did that the OCP or OVP kicked in on the main PMIC before any damage was done (to the SoC, Ram, EMMC etc) though you can check this by measuring the resistance between the SYS rail and 1V8PDR.
I’d just pull them and see if the shorts clear and worry about the reballing later
Mostly got over the course of prior board repairs, over time you memorize these rails normal measurments relative to ground and don’t even have to check against a known good, there is only a handful of critical rails which pretty much all roads lead back to, so doesn’t take long