HI all,
I’m tryng to repair a Switch that was opened before from someone else.
I see that is drawing current but it doesn’t boost to 1A and not turning on(black screen).
I found 2 shorted lines,one that leads me to take off P13USB and one short gone(yeah).
but now i’m struggling with the second short and it’s just a pain.
It’s the capacitor under M92T36,the one linked to PIN18.
Things that i have done: removed P13USB-M92T36-cap under M92-LCD connector(was damaged)
I injected 1,4V at 1,5A but i saw only M92T36 heating around pin 18 with thermal camera.
Hmmm i’m pretty lost,what else can i do?
How can i test Tegra just to know that is 100% fried?
OR any ideas?
THANK YOU ALL
Have you check if that cap on pin 18 is good? Also i would check BQ next
Hi Integ209,thank you for reply me🙋🏻♂️,
Yes i have removed cap and value is good(1micro Farad),but short is still present on the pads.
I will re-check BQ and post results
1v8 VDDIO is a pain because it involves many power regulators(Maxx+),i hope that Soc is not fried,but anyway at the end is good experience that we can share.
On the backside above the Realtec ALC6639 ic is a tiny ‘EN’ ic. I would check the red markt cap next to it if it is shorted.
Hi Calvin,
The cap near EN chip,reads 0.540v on the right side,and 0v from left side,DMM in diode mode,red probe on ground🙋🏻♂️
I’ll try to post pics of the board with the caps situation as soon as i can,maybe tonight,cause i’m new to the forum and i can’t upload images in the board,
First Switch in my life and i’m sweating:sweat_smile:
And this is the motherboard situation at the moment.M92T36,P13USB and LCD fpc connector are OFF at the moment.I found some strange things here and there
What do your green and red circles actually represent?
Solder blob you should clear up with your iron regardless.
Kind of looks like someone has used this as a donor.
Red is for shorted caps,green for good caps and inductors around chips.
This Switch is not mine,and yes when i opened it i had a bad feeling but you know i love repair so i gave it a chance,and at least is always practice and experience.
But i don’t want to gone mad,is there a way to test if the Soc or nand are 100% toasted?
K, can you provide your resustance to ground (ohms) at the max77620 on the caps you’ve highlighted as shorted?
It’s pretty obvious somebody has reworked this IC, so either they knew what they were doing (this is what I’d do) or they didn’t and messed up reballing the IC… your hoping for the second 
Your short on 1V8PDR is concerning though, does it remain shorted with the EMMC removed? or maybe it’s being cause by the above.
yes
It appears that this young guy brought his switch to a china repair shop,and they told him that was fixable for 80 bucks.Maybe they scammed him,or maybe he lied to me buying junk from Ebay,who knows.
So i’m trying to toss a coin and see,really nothing to loose at this point.
However it goes,next week i will return the Switch to its lucky owner
yap short still remains without EMMC
K, remove this IC
And see if that 1.5 ohm short on the cap nearby clears and also the short on 1V8PDR.
If it does, you’ve found the problem
You should clear up that solder blob first though if you haven’t done so already.
wow look at this mess…
And now the moment of truth…heart beat…and…short is gone!!
Can’t believe it man,but it’s not over,i need to replace IC’s and measure voltages correct?
Anyway thank you so much Severence and also Calvin and Integ209, this means so much to me,
hope that can helps other guys that love repair stuff like us
That’s great news 
Right, you’ll need to pick up some stencils and solder paste and salvage this IC from a donor, I don’t think you can buy them preballed afaik unfortunately.
After replacing, I’d measure the resistance to ground on the surrounding components, and if everything checks out compared to a knnown good you can power up the board and hopefully it will work
Can’t wait,i’ll do my best,but I am happy in any case I am satisfied because I have learned a lot.
I will keep you updated on developments.
PS: by any chance do you know the value of the missing capacitor on the back of the soc?
I measured 5.7 µF at this cap, but I couldn t find a matching cap at mouser.
Hello Calvin this is interesting… my sample book stop at 1micro farad ±10V (0402 size) dam 
Did you test cap on board?
I desoldered the cap and tested it outside the circuit. I think it may be a 4.7 µF.
yes it should be fine thanks a lot I appreciated it