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Вы здесь » Ремонт ноутбука своими руками. » Samsung, Dell » Dell inspiron N5010 UMA immediate short when plugged in

Dell inspiron N5010 UMA immediate short when plugged in

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  • Автор: mohkamtun
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    05.11.2015 19:17:35

Platform : dell_inspiron_n5010_wistron_berry_dg15_intel_discrete_uma

Got Dell for repair, initially with constant reboot and no display.
Changed shorted +VCC_CORE  and +VGA_CORE outputting fets.
Also, replaced failing ISL62883HRT with a working recovered one.

Now, when plugged in, adapter light shuts immediately and PTC4702-PTC4703-PTC4706- PTC470 short.
Replaced them 2 times with no avail.

-What is likely to make outputting electrolytic caps to short and short again, knowing that  ISL62883HRT was already replaced ???

Thanks

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  • Автор: freeqwer
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The processor was changed with a known good ?
What is the resistance on PL4701 ?

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  • Автор: mohkamtun
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Hi freeqwer

freeqwer написал(а):

Processor was changed The with a known good?

Yes, with no avail.

freeqwer написал(а):

What is the resistance on PL4701?

87 Ohms with CPU fixed
65 Ohms with  CPU removed, very low ??? should be hundreds of ohms, do you agree ?

Any suggestion

Отредактировано mohkamtun (21.09.2015 15:02:15)

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  • Автор: freeqwer
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mohkamtun написал(а):

should be hundreds of ohms, do you agree ?

yes

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  • Автор: mohkamtun
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Hi Freeqwer

Found PU4702 shorted again though already replaced. Removed it and measured Resistance to GND on PL4701, PL4702 and PL4703, found always 87 Ohms with CPU installed.

Removed one leg of each coil i.e PL4701 PL4702 PL4703, found with GREAT SURPRISE over 0.180 kohms resistance to gnd before and after the coils;

Re-soldered coils, and measured again coils'resistance to GND found 0.220 kohms!

Couldn't understand why coils'resistance to gnd became normal, just after removal of one leg and resoldering it back ? I guess some discharge took place when legs were removed!

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  • Автор: mohkamtun
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Hi freeqwer

Further to my last post, replaced PU4702 and faulty caps and powered lap, without CPU, fan spinned  for 30 seconds then stops and lap switched off !!!

The 6 caps and fet PU4702 just replaced were found short again with PU4703!!!

Have to trace and figure out what is causing repetitive short to caps and fets before powering it again.

QUESTION : Is there a method for trying on lap without risking a new short for fets and caps replaced, that will be very helpful ???

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  • Автор: freeqwer
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mohkamtun написал(а):

QUESTION : Is there a method for trying on lap without risking a new short for fets and caps replaced, that will be very helpful ???

Possible causes of fault :

- faulty PU4701 (i.e. the PWM controller opens the top MOSFET PU4702
and not closes it . In this case, through the MOSFET flows a large current. And MOSFET is burned. )

- was faulty itself PU4702
- was faulty processor
- load (the fact that after PL4701) has too low resistance

Also check the feedback (lines after PG4708 and PG4706)

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  • Автор: mohkamtun
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freeqwer написал(а):

Possible causes of fault:

- Faulty PU4701 (ie the PWM controller opens the top MOSFET PU4702
and not closes it. In this case, the MOSFET through a large current flows. And MOSFET is burned.)

- Was itself faulty PU4702
- was faulty processor
- load (the fact that after PL4701) has too low resistance

Also check the feedback (lines after PG4708 and PG4706)

Hi Freeqwer!

I put aside Dell n5010 under repair since last week (Aïd, our religious celebration), so couldn't give any feedback earlier!

Anyway, thank you for your good explanation regarding what causes caps and fets to be shorted.

UPDATE :
It turned out that PU4706 was shorted (3rd phase VCC_core output).

New steps taken :
-Replaced PU4706 and all shorted caps and fets.
-Removed PU4707 and PU4708 to help identify which output Phase is causing immediate short.

Powered up lap without CPU, adapter shut down immediately!

Found shorted only :
PTC4702 , PTC4704 and PTC4705
All fets are checked OK. improvement !!!

http://s3.uploads.ru/t/p3n7I.png

Now have to trace out what is causing PTC4702 alone (PHASE1) with PTC4704, PTC4705 (PHASE2) to fail again ?

, As I'm getting closer and closer to the final solution, I don't want to give up.

1*-So, please, given the new situation, any suggestion as where and how to dig further, should be very much appreciated!

2*-Is there a method for trying on lap, without risking fets and caps to be shorted again ?

Thank you for your your continued support!

Отредактировано mohkamtun (01.10.2015 14:03:28)

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9

  • Автор: freeqwer
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Look similar :
You had a faulty PU4707 PU4708

They could be burned as a result of what was faulty PU4706
As PU4706 controls the gates PU4707 PU4708.
And if PU4706 faulty, it opens the gates (not voltage regulation) PU4707 PU4708 and through them flows a large current and they are burned.

Now you have defective PTC4702, PTC4704, PTC4705
PTC4704, PTC4705 installed in the circuit with PU4704 and PU4705 .
LGATE2 and UGATE2 are managed through PU4701
Accordingly , you need to check all of these circuit elements.

PTC4702 is in the chain PU4702 and PU4703
They are managed by the same PU4701

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