Overheating IC - Chip on motherboard labelled 2250 EmFC overheating when plugged in to mains.

Thread Starter

harrlyald

Joined Sep 14, 2021
8
I have a motherboard which does not charge the battery properly. When it is plugged into the mains, a chip labelled 2250 EmFC gets immensely hot. Please advise.
 

zophas

Joined Jul 16, 2021
137
Not enough info to help you. Is it a washing machine, a alarm system, a power supply, a pop corn machine, a computer, a television?
 

zophas

Joined Jul 16, 2021
137
Yeah, the insides of a netbook would be beyond my meager technical knowhow. But I'm sure there are others that may be able to give you some advice. Thanks.
 

Deleted member 115935

Joined Dec 31, 1969
0
sounds like a
capacitor,
may be a picture / size of might help

could be 22v, 50 uF
 

Irving

Joined Jan 30, 2016
2,173
Not really, can you get a closer, in focus, image, of U40, and identify some of the devices around it, eg the device immediately above it as well as U11, P01, P02 etc. The naming is weird - Uxx usually designates a complex multifunction device, while Qxx is usually a transistor/MOSFET, but its not clear what Pxx are (though they appear likely to be MOSFETs). Its an educated guess, but I'm thinking that's a voltage regulator, though its an unusual package for one. It's definitely related to the USB-C port below.

Incidentally the red 'dot' above and to the right is a test point for a power rail V3P3SX1 is clearly 3.3v (the other to the left is V5P0A1, 5.0v)
 

Thread Starter

harrlyald

Joined Sep 14, 2021
8
Hope this is better. There is no power on the 3.3v or 5v power rails. I do believe there is a short as some capacitors are beeping on both sides (diode mode).

1631705508154.jpg
 

Irving

Joined Jan 30, 2016
2,173
That helps a little bit... What's missing from the picture are any inductors - fundamentally part of this switching regulator setup - so is there anything on the back of the board? What we have here is a collection of custom parts - or at least a family of parts from one of the many obscure far-east chip houses that only supply OEMs that generate 5, 3.3, 1.2 and 1v (from test points) and maybe others - so far I've not found a meaningfully matching data-sheet for any of the devices.

Its a high possibility that the 2250, whatever it is, is in itself faulty, but its heating is symptomatic of another device failure elsewhere, probably a shorted capacitor. The quality of the soldering on that board leaves much to be desired.

Another thing that's unusual is putting pin numbers on the silkscreen as well as the dot signifying pin 1. Can't say I've seen that before!

Can you say what's written on P01, P02, etc?
 

Deleted member 115935

Joined Dec 31, 1969
0
Whats the history of the board ?
Has some one been at that board , with a soldering iron of such like,
there are some not very good looking joints there,
 

Irving

Joined Jan 30, 2016
2,173
So Pxx means a P-channel MOSFET, which are AON7403 and matching N-channel, Qxx, are AON7410. Still nothing matching the 2250 or the 7601 devices.

As I thought, inductors on the back of the board!
 

Irving

Joined Jan 30, 2016
2,173
You think one of the inductors could be an issue?
Very unlikely. Given you have no 5v or 3.3v (and I guess no 1.2v or 1v either) there's no power getting to any of the switching regulators. The most likely culprit is a shorted capacitor on the input side since only the 2250 is getting hot. Normally a failed MOSFET doesn't get very hot as either it's a dead short or it's gone open circuit. I'm guessing the 2250 is some form of input side switch controlling the charging but TBH it could equally be a switching controller, though the 7401 is the more likely candidate for that. Without datasheets or looking more closely at the board and tracing some connections it's hard to say exactly.

Does it run on batteries? Is the problem only running on the charger?
 

Thread Starter

harrlyald

Joined Sep 14, 2021
8
No it does not. The problem is that the laptop does not switch on at all. With regards to running on battery power, it could just be that the battery is dead.
 
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