Fixing a cellphone??

[mike]

I have a Samsung Stratosphere smart phone.
I use it as a tablet.
When I turn it on, it starts to boot, hits the
splash screen then
goes into a loop where it just displays "SAMSUNG"
over and over.

The usual three-fingerpress boot methods don't help.

If I put it in the fridge for a while, it boots
and runs until I accidentally hit the power switch
and shut it down.

I'm thinking about tearing it apart and looking for
bad caps not being able to handle the power surge
of everything coming up at once.

I have an electrical engineering degree and a ton
of equipment. I've done a few GPU reflows on laptops.
I have infinite free time, but lack motivation ;-)

Is there any chance I'll be able to fix this thing?
At least it sorta works now.

Any good tutorials on smartphone repair tactics?

[amdx]

I think your luck may be with a can of freeze mist.
Just dribble the liquid on to just one part at a time until it boots up.
Someone may have more knowledge about what area of the board may be
more suspect, therefore the place to start cooling parts in first.

Mikek.

[Jeff Liebermann]

On Thu, 21 May 2015 13:52:36 -0700, mike <ham...@netzero.net> wrote:

>I have a Samsung Stratosphere smart phone.

>I'm thinking about tearing it apart and looking for
>bad caps not being able to handle the power surge
>of everything coming up at once.

You won't find any bad caps. My guess is you'll find water damage and
green slime (corrosion) especially in the battery contact area.

>I have an electrical engineering degree and a ton
>of equipment.

I have the same problem. Everything I learned in kollege is now
obsolete and 5 years of junk accumulation has ruined my ability to fix
things. By coincidence, I'm now doing a purge and recommend you do
the same.

>I've done a few GPU reflows on laptops.

Did the laptop work afterwards?

>I have infinite free time, but lack motivation ;-)

I usually have either time or money, not both. Motivation tends to be
proportional to either the money, or the entertainment value.

>Is there any chance I'll be able to fix this thing?

No. You lack motivation. Cell phone repair is not easy, especially
without schematics and replacement parts. Most everything is on one
big board, which means that plugging in modules doesn't really help.

>At least it sorta works now.

If it ain't broke, you are not trying hard enough.

>Any good tutorials on smartphone repair tactics?

<https://www.ifixit.com/Device/Samsung_Stratosphere>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Jeff Liebermann]

On Thu, 21 May 2015 16:24:19 -0500, amdx <noj...@knology.net> wrote:

>I think your luck may be with a can of freeze mist.
>Just dribble the liquid on to just one part at a time until it boots up.

I beg to differ. MLCC (multi-layer ceramic cap) don't like thermal
stressing and will fracture and short. I killed a few larger size
MLCC caps that way. You can also do the same type of thermal damage
with a soldering iron.
<https://www.google.com/search?q=mlcc+thermal+crack&tbm=isch>
<http://www.murata.com/en-global/support/faqs/products/capacitor/mlcc/mnt/0007>
Most of the warnings are for soldering, but I believe the problem also
exists for freezing.

>Someone may have more knowledge about what area of the board may be
>more suspect, therefore the place to start cooling parts in first.

I see some corrosion and water damage inside cell phones and tablets.
I managed to partly destroy my Motorola Droid X2 by using it in the
high humidity bathroom while showering.

[mike]

On 5/21/2015 4:06 PM, Jeff Liebermann wrote:
> On Thu, 21 May 2015 13:52:36 -0700, mike <ham...@netzero.net> wrote:
>
>> I have a Samsung Stratosphere smart phone.
>
>> I'm thinking about tearing it apart and looking for
>> bad caps not being able to handle the power surge
>> of everything coming up at once.
>
> You won't find any bad caps. My guess is you'll find water damage and
> green slime (corrosion) especially in the battery contact area.
>
>> I have an electrical engineering degree and a ton
>> of equipment.
>
> I have the same problem. Everything I learned in kollege is now
> obsolete and 5 years of junk accumulation has ruined my ability to fix
> things. By coincidence, I'm now doing a purge and recommend you do
> the same.
>
>> I've done a few GPU reflows on laptops.
>
> Did the laptop work afterwards?

First one was a learning experience.
I tried to go commando and wing it.
Had to manage two heat guns and some thermocouples.
I'd used paper towel under the foil heat shielding.
Trying to put out the fire dislodged some components...game over.

I built a fixture to control air flow and mounted the heat guns
so had a free hand and put on several thermocouples.
Second two I tried still working fine.

Got two more laptops to be done, but I've already got so many
working laptops that I don't need two more...low motivation.

>
>> I have infinite free time, but lack motivation ;-)
>
> I usually have either time or money, not both. Motivation tends to be
> proportional to either the money, or the entertainment value.
>
>> Is there any chance I'll be able to fix this thing?
>
> No. You lack motivation. Cell phone repair is not easy, especially
> without schematics and replacement parts. Most everything is on one
> big board, which means that plugging in modules doesn't really help.
>
>> At least it sorta works now.
>
> If it ain't broke, you are not trying hard enough.
>
>> Any good tutorials on smartphone repair tactics?
>
> <https://www.ifixit.com/Device/Samsung_Stratosphere>

Thanks for the link. At least I'll know how to get it apart.

If it's a mechanical problem, why does it keep working when it
gets hot? and continues to work after a long sleep when it's cool.
Still thinking it's a brown-out problem with the power supply going
out of regulation when the screen first comes on and it's trying
to start up everything. I oughta be able to see that on the scope
while it's in the boot loop.

I'm also worried about fracturing stuff with cold spray.
Thinking about applying the freon to a Q-tip and touching
parts with that.
>

[Jeff Liebermann]

On Thu, 21 May 2015 21:02:53 -0700, mike <ham...@netzero.net> wrote:

>> Did the laptop work afterwards?

>First one was a learning experience.

Welcome to Learn by Destroying(tm). You seem to be learning.

>I tried to go commando and wing it.
>Had to manage two heat guns and some thermocouples.
>I'd used paper towel under the foil heat shielding.
>Trying to put out the fire dislodged some components...game over.

Ummm, yeah bad idea. Aluminum foil works well but two heat guns is
not a good way with BGA chips. You might try a toaster oven. I've
only done two HP laptop motherboards with the toaster oven. Both
recovered just fine.

Some LaserJet boards with the traditional crappy BGA soldering. I did
14 JetDirect boards and all worked when done.
<http://802.11junk.com/jeffl/pics/repair/BGA%20reflow/index.html>

>I built a fixture to control air flow and mounted the heat guns
>so had a free hand and put on several thermocouples.
>Second two I tried still working fine.
>
>Got two more laptops to be done, but I've already got so many
>working laptops that I don't need two more...low motivation.

Just flex the laptop motherboard a little. That should give you a
failed laptop to practice your reflow soldering.

>>> Any good tutorials on smartphone repair tactics?
>>
>> <https://www.ifixit.com/Device/Samsung_Stratosphere>
>
>Thanks for the link. At least I'll know how to get it apart.

For cell phones, you should probably buy a cheap USB microscope
camera. I have one that I don't recommend, but there are plenty
available on eBay and Amazon. You may need to experiment with the
power, size, illumination, etc. Be sure to get something with an LED
illumination ring around the imager.

>If it's a mechanical problem, why does it keep working when it
>gets hot? and continues to work after a long sleep when it's cool.

I have no idea. Offhand, my guess(tm) would be (in order):
1. Bad soldering, cracked solder connection
2. Broken trace
3. Cracked MLCC capacitor
4. Dirt, crud, corrosion, filth, and metal shavings.

>Still thinking it's a brown-out problem with the power supply going
>out of regulation when the screen first comes on and it's trying
>to start up everything. I oughta be able to see that on the scope
>while it's in the boot loop.

That's possible, especially if the battery is dead or defective.

>I'm also worried about fracturing stuff with cold spray.

The freeze spray will drop the temp by about 75C. A soldering iron
tip will produce about a 160C temp rise. You're much more likely to
kill MLCC caps with an iron than with freeze spray. Still, you should
be careful.

>Thinking about applying the freon to a Q-tip and touching
>parts with that.

Ozone depleting Freon has not been used in freeze spray for maybe 20
years. Tetrafluoroethane is what's used these daze.

[mike]

On 5/22/2015 8:12 AM, Jeff Liebermann wrote:

>> Thinking about applying the freon to a Q-tip and touching
>> parts with that.
>
> Ozone depleting Freon has not been used in freeze spray for maybe 20
> years. Tetrafluoroethane is what's used these daze.
>
>
>

I've had this can of freeze spray for 30 years or more. ;-)