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Tablet charging problem

Griffinballs

Jul 23, 2015
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Jul 23, 2015
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Hello yet again all.
Pretty sure this is my last problem for a while. I just keep remembering all the broke stuff we've got.

Next up we have a Samsung galaxy tab pro 10" that has a charging issue. It started as a standard charging port replacement as my kids messed about with it too much plugged in and it no longer charged.
Got a replacement socket ready to go on a pcb so it was a simple clip in job. At the time I wondered about it being a crappy copy and that's prob the main issue here. At first it worked and charged normally for about a day.

Now the tablet charges but only at its low voltage rate, it says the power supply isn't powerful enough no matter what one we use, even the 2a that came with it.

I'm guessing it's got something like a leaking cap that is causing the lower voltage or something and wondered if any of the lovely folk here may have an idea.
Pics on request as don't really know what to photograph yet as the socket is only a pass through ribbon cable job, there aren't any electronics on it, also I've already got a new one of those and it didn't help.

Thanks for any light that can be shed
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
I assume you're charging via a USB cable. Have you tried another cable? The data pins in the USB cable are used to communicate the chargers capability to the device being charged. The problem could also be at the USB ports on either the charger or the tablet.
 

Griffinballs

Jul 23, 2015
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I've used many chargers and USB cables , like 5. It's not the charger or USB cable.
The USB port is the bit I've changed twice.
As I said, when I first changed it, it worked as it should charging at the normal rate but within 24 hours it had changed to permanently charging at the lower rate, another new socket doesn't change it back to normal so I'm assuming it's blown something in the tablet.

So what causes the voltage to drop from where it comes in at the USB socket? The USB function of the tablet works as normal
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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stored the USB port you replaced still work as a USB port?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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25,510
OK, the problem is not a voltage drop, it is that the tablet is not recognizing the charger as capable of > 100mA (or maybe 500mA).

There are several likely possibilities:
  1. The charger is broken or not sending the appropriate signals (you have eliminated this by trying several chargers)
  2. The cable from the charger to the tablet is faulty (you have eliminated this by telling me that the cable works as a USB cable)
  3. The connector to the laptop is broken/miswired/faulty (you have eliminated this by replacing it -- twice)
  4. The tablet is not sensing the status of the charger
  5. The tablet has some sort of BIOS setting to reduce the charge rate.
  6. The port you plug the charger into does not act as a USB Port
Assuming you have correctly eliminated those things you claimed to have, it only leaves (4) , (5), or (6) as possibilities.

I am dubious that (5) could be the issue, and your answers suggest (6) is not a factor, thus the only likely option left is that the tablet has been damaged.
 

Griffinballs

Jul 23, 2015
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Considering that, I'll try again when I get home to answer the questions as maybe I've been mistaken in the way I've remembered the fault.

But yes if so you are correct, the tablet is damaged, my point is what about it, what on a circuit board can cause these symptoms. What can cause what should be 500ma to only read a 100ma. A dodgy cap, a blown diode? That's the only question I really needed answering
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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well you can look on the board and see if there are any burn marks.

There's no 500mA reading as 100mA. The tablet is simply deciding not to draw more than 100mA. It is doing this because it can't determine the charger is capable of more than 100mA (which is an amount all USB interfaces must be able to deliver).

I can say that it's most unlikely to be something as simple as a cap or a diode.
 

Griffinballs

Jul 23, 2015
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Main reason I thought it was something that blew is because bear in mind. Before I changed that socket, if I would get the lead in the right position it would work fine. It's only since swapping the port that the issue arose
 

Alec_t

Jul 7, 2015
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I'm guessing the tablet has a current sense resistor somewhere and monitors the voltage (only a few mV probably) across that to sense the current going into or out of the battery. If that resistor or the monitoring arrangement is faulty then the tablet may well be fooled into thinking that the charger can't provide enough current.
 

Griffinballs

Jul 23, 2015
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Now that sounds bang on the type of thing I was hoping for.
Can't get my hands on it for a few days now, Mrs has gone away with it. But once it's back ill rip it apart and see what we can find and report back.
Thanks guys, very helpful
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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It might sound "bang on", but it's actually about as likely that the parallel thronomister has phase leakage. Almost any phase inverting, precision thronomister will work in these types of devices. Just go into any good electronics store and ask for one.
 

pebe

Sep 3, 2013
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Sep 3, 2013
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I think the problem is due to a change of impedance between two points.
 
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