What procedure do you take

[Jane]

Hi guys,
What procedure do you take if you need to repair a dead tablet/mobile phone?
Suppose there is no a schematic available?
As far as I understand there can be a hardware or software reason.
It is a good start to check voltages but if you do not know what values ( and where)they should be , it is not workable.Replace to a power chip?
Maybe you can check if the device is taking any voltage from a power supply or not.If so, try to to reflash? What kind of flash to choose? According to CPU type or eMMC/flash type?
Any ideas?
Thanks

[goontron]

Re: What procedure do you take

There are many kinds of "dead" you need to be more specific.

[Jane]

Re: What procedure do you take

By being dead I mean that it does not start ( black screen, not being broken), so that a user can not use it. E.g. a tablet that stopped working.

[ktmmotocross]

Re: What procedure do you take

check for voltage on regulators. u find it in schematic

[Jane]

Re: What procedure do you take

As I pointed out in the question,
...Suppose there is no a schematic available?

If there is a schematic, yes, the first is checking voltages. But if not,
what then???

[stj]

Re: What procedure do you take

start with a beer and expectation of failure.

then open it and look at it very closely - a lot of problems are caused by liquids getting inside and messing up switches or connectors.

the big home button on iphones had that a lot - it was only sealed by a layer of sticky-tape and often got wet when people had wet hands - in rain or a kitchen for example.

[diif]

Re: What procedure do you take

start with a beer and expectation of failure.

then open it and look at it very closely - a lot of problems are caused by liquids getting inside and messing up switches or connectors.

Summed up brilliantly stj although I plug in one of those USB volt/ameters to see if it's drawing any current.

You're going to need more tools too depending what you have already.

[Jane]

Re: What procedure do you take

Visual inspection does not show anything unusual( even under microscope).

And now two possibilities.
1) by connecting to power supply, it draws some current
2)by connecting to power supply, it does NOT draw any current

How to continue next?

[Jane]

Re: What procedure do you take

Nobody knows?

[caspian]

Re: What procedure do you take

drawing current is not much helpful in repair.
when there is no schematics available, you have to find datasheet for each individual IC on the board. then check voltages on its pins.

[jiroy]

Re: What procedure do you take

How to deal with a Laptop when there are no schematic ? ..
First , write down the main Chipsets onboard , including the bq , rq , rt , etc ...Then locate their circuit diagrams and schematic , mostly treated like any other electronic component , on most Electronics sellers sites .
Upon completing a comprehensible list , you'll have a solid ground to check for compared voltages .

Second , locate regulators and Zener diodes , they are easy to reveal their voltages .

Third , buy a schematic ...(just kidding ) ..