Switch (MAX77812) cannot get pass 1st Stage Boot with current reading 116mA

[hengtoo]

Hi, I have a switch with MAX77812 chipset that draws 15V 0.46A (unassembled) but NO display and NO boot.

After opening it up, I notice that there's a crack on the MAX77812 power module and on the inductors.

Before swapping out the "obvious", I followed the guide from retrosix.wiki and on 1st stage boot, my switch was drawing 116mAh (nowhere near 200mAh) and was convinced that it's the MAX77812 so I swapped out to a brand new chip.

After swapping just the MAX77812 out 3 times, I was still getting the same result... so I'm sure you'll probably be asking why didn't swap out the inductors... well, I took measurements of the inductors (Red and black probe swap) and the resistors reading came out "close" so I assume that they are still "good"... On top of that, I really got NO idea what's the specs of those inductors are despite "googling" around... LOL

I'm totally "stumped" at this point and wondering if you kind folks out there
(1) know what's the specs of the mentioned inductors and where to get them.
(2) know what else could be the problem other than the MAX77812. I have tested M92 and P13USB with found no shorts. There are several shorts on my MAX77620H but not sure if it's related on the MAX77812 chip.

So far it's been 2/2 failures on my Switch fixes and I would really want to at least get this one fix haha.

Any help on the matter is greatly appreciated.

Explanation on attached pics:
(1) 15v, 0.4A draw on device
(2) the original condition of MAX77812 and surrounding area
(3) retrosix.wiki site "convincing" me that it's the MAX77812 that's at "fault"
(4) picture of MAX77812 area after chip replacement
(5) resistor measurements on inductors (Red is black on ground, Blue is red on ground)
(6) Diode Test

 

[leerz]

fix the shorts, lift the chip if it relieves the short, also the coils will give low imp, not always a short or deadshorts if using diode mode.

do you get 3v ?
also plug in to pc to see if your emmc is good (bad emmc will trigger rcm regardless if it's ipatched and marikos)

 

[hengtoo]

Appreciate the reply leez!

I did a RCM test and it did trigger RCM. Following "FixMyApp" (similar to RetroSix) guide, it could be
- Bad M92T36 IC
- Bad eMMC module

I then did a diode test around M92T36 IC area and all seems good except
- 2 small one (ie in light blue box) where neither side has any beep
- a small chip on the M92T36

Can anyone confirm that the small cap (ie in light blue box) suppose to "behave" that way?

Going forward, I'm thinking of
(1) Replacing the M92T36 chip and retake measurements
(2) LAST resort, re-flow eMMC module (End Game =) )

Any suggestion or advice?

Post automatically merged: Jan 16, 2024

Sorry if I'm stating the "obvious" to some of you folks but just that every time I try to do something to the console, I messed up other parts... like I did with the MAX77812 chip.... I knock out 6 caps and 1 resistors "along the way" Took me 1 FULL day to find the parts "scattered" around the board and hot air them back onto the board!!