Hardware Dead switch, capacitor/m92t36/p13usb questions

[vanillajackson]

Hi, I know there are a ton of threads about bricked switches so I'm sorry if this has been asked before. I have a switch here that is completely lifeless. Plugging it into the dock causes the light to flash once and then nothing. I think the m92t36 or the p13usb chip is bad.

The battery will charge, the m92t36 and the bq chip get warm when plugged in. When I first got the switch I measured the battery voltage and got 3.4v, after leaving it plugged in for a while the battery now reads 3.7v. But no other signs of life. I get 4.4v on pin 5 of the m92t36, but the cap connected to pin 6 is shorted to ground on both sides, and seems to be the only cap that is shorted around that chip. I found a video of a guy saying something about a cap near the m92t36 being shorted when the p13usb is bad, but I can't find it now. I checked the components near the p13usb and found that the bigger cap in the center of the attached photo is also shorted, and so are the 4 small caps(or whatever they are) on the other side of the chip.

Seems to me that the p13usb is more likely to be bad. But I'm not sure, so I just wanted to check here. Will replacing the chip remove the shorts? Or will I need to replace the caps too? Could the m92t36 cause this? Thanks.

 

[Pintglass]

Hi, I know there are a ton of threads about bricked switches so I'm sorry if this has been asked before. I have a switch here that is completely lifeless. Plugging it into the dock causes the light to flash once and then nothing. I think the m92t36 or the p13usb chip is bad.

The battery will charge, the m92t36 and the bq chip get warm when plugged in. When I first got the switch I measured the battery voltage and got 3.4v, after leaving it plugged in for a while the battery now reads 3.7v. But no other signs of life. I get 4.4v on pin 5 of the m92t36, but the cap connected to pin 6 is shorted to ground on both sides, and seems to be the only cap that is shorted around that chip. I found a video of a guy saying something about a cap near the m92t36 being shorted when the p13usb is bad, but I can't find it now. I checked the components near the p13usb and found that the bigger cap in the center of the attached photo is also shorted, and so are the 4 small caps(or whatever they are) on the other side of the chip.

Seems to me that the p13usb is more likely to be bad. But I'm not sure, so I just wanted to check here. Will replacing the chip remove the shorts? Or will I need to replace the caps too? Could the m92t36 cause this? Thanks.

Have you got a full short to ground on the large cap above PI3USB do you get close to 0 ohm's on both sides of the cap?

 

[The Real Jdbye]

Hi, I know there are a ton of threads about bricked switches so I'm sorry if this has been asked before. I have a switch here that is completely lifeless. Plugging it into the dock causes the light to flash once and then nothing. I think the m92t36 or the p13usb chip is bad.

The battery will charge, the m92t36 and the bq chip get warm when plugged in. When I first got the switch I measured the battery voltage and got 3.4v, after leaving it plugged in for a while the battery now reads 3.7v. But no other signs of life. I get 4.4v on pin 5 of the m92t36, but the cap connected to pin 6 is shorted to ground on both sides, and seems to be the only cap that is shorted around that chip. I found a video of a guy saying something about a cap near the m92t36 being shorted when the p13usb is bad, but I can't find it now. I checked the components near the p13usb and found that the bigger cap in the center of the attached photo is also shorted, and so are the 4 small caps(or whatever they are) on the other side of the chip.

Seems to me that the p13usb is more likely to be bad. But I'm not sure, so I just wanted to check here. Will replacing the chip remove the shorts? Or will I need to replace the caps too? Could the m92t36 cause this? Thanks.

If one of the caps is shorted, that cap may be bad. But if all the caps are shorted, it's likely the chip itself is bad. So your guess is probably correct, but if you replace the P13USB and you're still having issues and that one cap is still shorted, you should replace the cap. Which isn't an easy thing to do as they're so damn tiny and they like to stick to soldering irons.

 

[Pintglass]

If one of the caps is shorted, that cap may be bad. But if all the caps are shorted, it's likely the chip itself is bad. So your guess is probably correct, but if you replace the P13USB and you're still having issues and that one cap is still shorted, you should replace the cap. Which isn't an easy thing to do as they're so damn tiny and they like to stick to soldering irons

If he has got a full short to ground on the 3v3 rail everything on that rail will show as shorted even if its just one cap or an IC. He will have to try and find which component it is by checking for something getting hot or by checking which component has the lowest voltage.

 

[vanillajackson]

Thanks for the replies. It turns out the cap on pin 6 isn't shorted. When I first tested the cap the motherboard was still in the case and had the battery connected. I went back and tested it since I had the motherboard out and that short was gone. So I'm definitely thinking it's the p13usb. Oh and yeah the cap near p13usb is totally shorted, it zeros out on my meter. Went ahead and ordered the chip so hopefully that'll fix it. I'll be sure to post back if it does. As long as I don't kill it trying to replace it. I've had good luck so far with small smt chips, but it makes me nervous. Thanks again for the replies.

 

[vanillajackson]

Ok, so I got the chip replaced, and it is now working... but only on the tablet. Plugging it into the dock causes the screen to go black, but it shows nothing on the TV. So I'm thinking that a pin or a few pins may have not soldered down. I really need a better hot air station. The one I have is an 858D+ from like 2012 and it's getting a little janky.

But anyway, the p13usb seems to have been the problem. At least one of them.

 

[Pintglass]

Check the filters running to the Pi3usb just above the usb port you should have continuity on all of them.