Hello,
I’m trying to repair the switch from my nephew. The switch only shows a black screen. The battery has 3.8V. I found a short on the left cap from the M92 which is going down to the P13USB. The big cap above the P13USB is also shorted and the P13USB seems to be blown. Unfortunately I’m not allowed to post pictures.
I removed the P13USB but the short is still present. Thus I also removed the M92 but the short is still present on both caps.
I also checked the filters of the P13USB and they seem to be fine. What else could it be? I heard that if P13USB and M92 is out and there is still a short then the CPU is dead? Is this correct? Or is there anything else which I can check? Around M92 there is no short of the big caps.
I would check the EN Chip and the both caps at the right. (ignore the red marking on the little cap on the right) The both caps to the right are shorted in your case. But you can check if one of them or the EN chip is the cause of the short.
Thank you for your quick response. I’m not an expert in this field. It’s the first time I removed such tiny chips. But as far as I see it, for the EN chip I would need a solder mask? Never worked with it. So is there a way to check this chip before removing it? Or does it mean, if both caps on the right are shorted, that the EN chip is the reason?
Unfortunately I can check this not before tomorrow.
if you have no exp dealing with tiny chip before,remove those 2x20uF caps instead.
FYI, 3.3v also goes to CPU, hopefully you dont end up having cpu short
Hi, thank you again for your advice. Like you said, both caps near the EN chip were shorted as well. I’ve desoldered both. Now the short to GND is gone. So no short to the pads of the two big caps, no short of the cap of P13USB and no short of the cap of the M92.
I’ve tested both caps. One buzzes and the other one seems to be okay with 21.8 uF. I would replace both, just to be sure. But what do I need? The schematics you showed says C0603_20uF. 0603 tells me the size and 20uF the capacity, but what about the voltage? I would try to get it on a local store and if they don’t have it, order it online.
Just wanted to report that replacing the two caps worked. I’m glad I bought 10 of them cuz at least 3 went flying cuz my tweezers send them away somewhere on my floor…
It was way more difficult to replace these two caps then the P13USB or the M92. Without a microscope and steady hand it took me a while to replace the two caps, cuz they are that close to each other. I also ended up to push them away a few times and they tended to stick on my tweezers.
Long story short: after replacing those two caps the short was still gone and thus I replaced the broken P13USB and used the original M92. Then I brought everything together and now everything works again. I get a video output again and the battery is charging. My nephew is happy and already tested it. It seems that everything works.
Thus, thank you very much for helping. Without your help I would not be able to repair it I guess.
