Tablet eStar Beauty MID7378W, overheats when off, reboots by itself

[panoss]

Purchased from Media Markt, October of 2017, still within warranty.
Symptoms:
1. when I turn it off and stays off, it gets warm ... (near the charging point at the back of the tablet and, I guess, the battery is somewhere around there)
2. when I turn it off, most of the times it DOES NOT remain off but ... it reboots itself …
If the battery charge level, when turned on, is too low ... it turns off itself...and of course it reboots and because the battery is low it turns off itself etc ... a vicious circle of reboots...

I went to the Media Markt service, they held it for two weeks, and returned it to me by simply...re-installing the firmware...

That is, they concluded that: overheating + repeatitive reboots = ... reinstallation of android ...

Because I do not think they are ignorant, they just want to get rid off me.
So, Media Markt and their service and their warranty are rated under zero...

I 'm not aiming going back to their...'service', it is obvious that they are not willing to repair it using the warranty and they will, by any means, try to charge me.

So I ‘m thinking of opening it and thying to find the source of overheating, a short-circuited component I suppose near the charging point. (the short-circuited component must be part of the sleep mode circuitry since it gets overheated only when turned off)
Has anyone else treated something similar with any tablet? (or, even better, with an eStar)

Any help is welcome.

[wraper]

1. when I turn it off and stays off, it gets warm ... (near the charging point at the back of the tablet and, I guess, the battery is somewhere around there)
2. when I turn it off, most of the times it DOES NOT remain off but ... it reboots itself …

Sounds like liquid damage.

[panoss]

What is the 'liquid damage'?
Could you be a bit more explanatory?

[wraper]

It means some liquid like water of beer got in and caused corrosion. Only one drop is enough if you are unlucky.

[panoss]

I must add that from the beginning (from day one) this tablet was not absolutely fine: usually (while off), when I would plug in the usb charger it would...boot!! But I ignored it, it was not something terrible.
I think this is what grew, slowly, day by day, to the current state and not some 'liquid damage'.

[wraper]

Excuse me, but many phones and tablets normally boot up when you attach the charger. You can even configure those which don't by default to do exactly that.
Turning ON by itself defect is like a sign of 95%+ probability that some liquid got in. And heating up while off just confirms it.

[panoss]

Ok, so some liquid entered the tablet and corroded some component or some traces on the pcb, this is why, even though the liquid evaporated (after such a long time I suppose it has evaporated) the tablet continues to warm up while off and reboot by itself.
Did I get it right?

[wraper]

Ok, so some liquid entered the tablet and corroded some component or some traces on the pcb, this is why, even though the liquid evaporated (after such a long time I suppose it has evaporated) the tablet continues to warm up while off and reboot by itself.
Did I get it right?

Mostly yes. I don't think that reboot is exactly because of the warm up as such, though. Warm up is just another consequence.

[panoss]

Ok, I 'll open it up and follow the heat. I suppose at the hottest point will be the source of my tablet 's problems...

My supposition that there must be some short-circuit in the sleep mode circuitry, does it sound logical?

[wraper]

There might be corrosion shorting balls under some micro BGA chip. You may look inside but without ultrasonic bath to clean the PCB, I doubt it will be an easy fix. Liquid damage repair can vary a lot. From a little of cleaning with toothbrush to nightmare of removing micro BGA chips and restoring pads which were eaten away by corrosion. In any case, heating up sure does not sound good.

[panoss]

Well...then I 'll leave it as is.
If I never turn it off, there is no warm up and no reboots.

So, I 'll just leave it on forever!

[wraper]

So, I 'll just leave it on forever!

FYI, if it's really a liquid damage (as I said, it's most likely but I cannot guarantee it of course), that crap tends to progress over time.

[panoss]

I hope it has stopped.
In case it gets worse, I 'll open it up.

[panoss]

It got worse, now it does not boot at all, so I opened it: RK3126 is the IC that overheats.
This is the CPU, so it goes to recycling, right?

[wraper]

If there is no liquid damage, why don't you return it for warranty repair again?

[panoss]

They 're not willing to make a real repair, if they where they would not 'repair' the overheating with...firmware re-installation  .
Any way, now I have opened it so the warranty is gone.

[wraper]

If it's completely dead, they cannot just flash the firmware again. As of taking apart yourself, I've took things apart many times and never had warranty rejected. You just need to be careful not leaving any traces.

They 're not willing to make a real repair, if they where they would not 'repair' the overheating with...firmware re-installation

Fault description which technician sees often has nothing to do with what customer really complained. If fault is intermittent, there is nothing surprising about how warranty was processed, especially considering you did not return it again. Not to say CPU could easily heat up because of firmware if CPU is run at fool speed for prolonged time, so there is nothing surprising if technician misunderstood complain. They also don't have much time to test things due to low cost.

[wraper]

When I worked at cellphone repair service in the past, most complains were poorly described by customers and/or poorly written by staff who receives items for warranty. Half of the technicians were idiots as well, so YMMV depending on particular person who get's the item.

[panoss]

Fault description which technician sees often has nothing to do with what customer really complained.

My description (and what was written by the clerk, so I suppose this is what the technician read) was:
'Overheats when off. Also, while off it boots by itself. And reboots constantly.'

It was too sort for the clerk in the reception to remove any word or change anything.

If fault is intermittent, there is nothing surprising about how warranty was processed,

The fault (well, the symptom, to be accurate) was not intermittent.

especially considering you did not return it again.

I did, but they said I 'd have to leave it for another 15 (at least) days  , I would have to pay for fault finding (it's a cheap tablet, doesn't deserve pay anything), so I didn't leave it for repair.

Not to say CPU could easily heat up because of firmware if CPU is run at fool speed for prolonged time, so there is nothing surprising if technician misunderstood complain. They also don't have much time to test things due to low cost.

As I said, it was overheating while off. So, the CPU did not run at fool speed not even for nanoseconds. It was in sleep mode.

Anyway, it's a cheap tablet so it doesn't really worth bothering anymore with it.

But the fact remains that MediaMarkt did not respond properly to the product 's warranty.

[wraper]

As I said, it was overheating while off. o, the CPU did nont run at fool speed not even for nanoseconds. I was in sleep mode.

I wrote that to explain why described fault could be misunderstood.

But the fact remains that MediaMarkt did not respond propely to the product 's waranty.

Very unlikely they do any testing/repair themselves.

[panoss]

I corrected my phrase, I had a few typos:
'As I said, it was overheating while off. So, the CPU did not run at fool speed not even for nanoseconds. It was in sleep mode.'

[panoss]

Very unlikely they do any testing/repair themselves.

They don 't do it themselves, they cooperate with an electronics service company.
This does not relieve MediaMarkt of its responsibility for the warranty.

[panoss]

SMD IC 6 pins, marked as: LPS 5A712.
I can't find it, does anybody know what it is?

Also I found a sort-cicuited SMD IC marked: LPS A37 and something else (it 's not visible), the IC is deformed and bulged.
This one has 5 pins.

Both these LPS ICs look like dc to dc converters, they are both next to SMD coils.
At the attachment you can see the LPS A37** (I 'm not sure it's 37)

How am I gonna find out which ICs are these?