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Вы здесь » Ремонт ноутбука своими руками. » Asus, Toshiba » Dead Toshiba NB200

Dead Toshiba NB200

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  • Автор: mohkamtun
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Hello, here I'm back.

Got a dead Toshiba NB200 for repair. Platform : KAVAA LA-5121P Rev : 2.0

Found both lines +3VALW and +5VALW shorted.
Desoldered PJ1 and PJ3 to isolate short issue.
Replaced bad RT8206B (SN0806081) with a good working TPS51427 and removed shorted E/C KB926QF, +3VALW line short is gone (PL4 to gnd=305R).
Replaced shorted PQ21 and PC60, +5VALW load line TO GND =16R.???
Traced this line and found VCC usb shorted to gnd : replaced bad C455, and removed U18 and U21 (USB power supply fets) found partially short, now +5VALW load line to gnd measures : 90R.???

Soldered back PJ1 and PJ3 and connected power adapter,  +5VALW and +3VALW are always absent, and PQ21 AND PC60 ARE SHORTED AGAIN.

Wish to get confirmed :
*1-I guess the 90R Resitance to gnd found on +5VALW line is not normal, do you agree ?
*2-Could +5VALW and +3VALW be issued for this platform, if mobo is powered with EC desoldered?
*3-What could cause the PQ21 and PC60 to short again ?

Many thanks for your help.

Отредактировано mohkamtun (11.04.2015 20:35:51)

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  • Автор: freeqwer
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mohkamtun написал(а):

I guess the 90R Resitance to gnd found on +5VALW line is not normal, do you agree ?

I don't really understand ?
Resistance lines +5VALWP equal to 90 ohms ?
In this case, it is a very small resistance .
Faster the line is leaking.

mohkamtun написал(а):

What could cause the PQ21 and PC60 to short again ?

The failure of PQ21 can be caused by faulty - PU6

mohkamtun написал(а):

Could +5VALW and +3VALW be issued for this platform, if mobo is powered with EC desoldered?

Did not understand the phrase.

+3VALWP +5VALWP should appear after connecting the power plug
the EC does not play a role here .

I think I need to shoot jumpers PJ1 and PJ3 and run the laptop without them.
+5VALW or +3VALW must rise to a high level.
If not , then look for the problem before PJ1 and PJ3
If the voltage went up, the problem after PJ1 and PJ3

+1

3

  • Автор: mohkamtun
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freeqwer написал(а):

I do not really Understand?
Resistance Lines 5VALWP + Equal to 90 Ohms?
In this case, it is a very small resistance.
Faster the line is leaking.

You guessed what I mean i.e the resistance of +5VALWP rail load to gnd is 90R. So +5VALWP  line is leaking.

freeqwer написал(а):

The failure of PQ21 can be caused by faulty - PU6

But I already replaced faulty PU6 (RT8206B) with a working TPS51427 and PQ21 and PC60 shorted again.

freeqwer написал(а):

Did not understand the phrase.

+3VALWP +5VALWP should appear after connecting the power plug
the EC does not play a role here .

Well, you did confirm that steps made are ok : I tried to solve +3VALWP and +5VALWP fail before replacing the bad KBC926 that I removed.

freeqwer написал(а):

I think I need to shoot jumpers PJ1 and PJ3 and the Run Laptop without Them.
5VALW + or + 3VALW must rise to A High Level.
If not, then Look for the problem before PJ1 and PJ3
If the Voltage Went up, after the problem PJ1 and PJ3

Already done, and that what helped me to identify USB short.

mohkamtun написал(а):

Found both lines +3VALW and +5VALW shorted.
Desoldered PJ1 and PJ3 to isolate short issue.

1*So, PJ1 and PJ3 jumpers removed but still +5VALW and +3VALW are absent, though LDO is +5.4V , EN1 and EN2 are ok (+1.14V and +2.5V)
2*-Might be the leakage on +5VALWP load rail blocks system voltages to be issued! Do you agree ?
3*-Could leakage on that rail cause short to PQ21 and PC60 ?
4*- Taking into account the investigations already made, where to dig further for the leakage and the failing system voltages?

Thank you

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  • Автор: freeqwer
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mohkamtun написал(а):

PJ1 and PJ3 jumpers removed but still +5VALW and +3VALW are absent

+5VALW and +3VALW must rise to a high level

mohkamtun написал(а):

Might be the leakage on +5VALWP load rail blocks system voltages to be issued!

yes

mohkamtun написал(а):

Could leakage on that rail cause short to PQ21 and PC60 ?

unlikely, less likely
although all can be

mohkamtun написал(а):

Taking into account the investigations already made, where to dig further for the leakage and the failing system voltages?

What resistance lines +5VALWP +3VALWP in remote jumpers PJ1 and PJ3 ?
What is the voltage on 1,5, 7 contact PU6 ?

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5

  • Автор: mohkamtun
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Hello,

freeqwer написал(а):

What resistance lines +5VALWP +3VALWP in remote jumpers PJ1 and PJ3 ?

Resistance lines in remote jumpers :
+5VALWP=90 ohms
+3VALWP=305 ohms

freeqwer написал(а):

What is the voltage on 1,5, 7 contact PU6 ?

1-Ref : +2.4V
5- V_Ref3 : +3.6V
7- LDO now : +1.2V not normal but measured most of the time +5.4V. Reflow of chip IC didn't help LDO voltage to be stable.

Also, might be interesting to know :
EN_LDO : +7.4V
EN1 : +1.10V
EN2 : +2.5V

Thank you for any comment.

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  • Автор: freeqwer
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mohkamtun написал(а):

1-Ref : +2.4V

should be 2 volts

mohkamtun написал(а):

V_Ref3 : +3.6V

should be 3.3 volts

mohkamtun написал(а):

LDO now : +1.2V not normal but measured most of the time +5.4V. Reflow of chip IC didn't help LDO voltage to be stable.

The LDO regulate at 5V If LDOREFIN is connected to GND

I think you have more problems with your multimeter.

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  • Автор: mohkamtun
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hello

freeqwer написал(а):

I think you have more problems with your multimeter.

Wish to precise that voltages mentioned in "post 5" were measured with a good working multimeter i.e :

1-Ref : +2.4V instead of 2V
2-V_Ref3 : +3.6V instead of 3.3V
3- LDO : +1.2V instead of 5V , LDOREFIN beeing grounded
4- Resistance lines in remote jumpers PJ1 and PJ3 :
+5VALWP=90 ohms

Should these bad figures pinpoint to a specific faulty device, knowing that RT8206B (SN0806081) was already replaced with a good working TPS51427 ?

Many thanks for your help.

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8

  • Автор: freeqwer
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mohkamtun написал(а):

Resistance lines in remote jumpers :
+5VALWP=90 ohms
+3VALWP=305 ohms

To remove PL4 and PL5.
To measure resistance.

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  • Автор: mohkamtun
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freeqwer написал(а):

To remove PL4 and PL5.
To measure resistance.

As said in my previous posts, PJ1 and PJ3 were already removed and +5VALWP=90 ohms and +3VALWP=305 ohms are measured after PJ1 and PJ3 so  +5ALWP load rail is likely to be still faulty, do you agree ?

0

10

  • Автор: freeqwer
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mohkamtun написал(а):

As said in my previous posts, PJ1 and PJ3 were already removed and +5VALWP=90 ohms and +3VALWP=305 ohms are measured after PJ1 and PJ3 so  +5ALWP load rail is likely to be still faulty, do you agree ?

I say need to remove PL4 and PL5 , and not PJ1 and PJ3 .
Then measure the resistance at the points 2 and 1 on the mount inductors.
When removing PL4 and PL5 we disable some elements of feedback

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  • Автор: mohkamtun
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freeqwer написал(а):

I say need to remove PL4 and PL5 , and not PJ1 and PJ3 .
Then measure the resistance at the points 2 and 1 on the mount inductors.
When removing PL4 and PL5 we disable some elements of feedback

Ok, thought it's almost the same. But, now I understand better where you are heading.
Will give a go and feed back soon.

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  • Автор: mohkamtun
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freeqwer написал(а):

measure the resistance at the points 2 and 1 on the mount inductors.

Feed back :
resistances found :

PL4 point 1 : 120 Ohms
      point 2 : 300 Ohms (measured after PL4)

PL5 point 1 : 120 Ohms
      point 2 : 100 Ohms (measured after PL5)

Where to trace fault then, so as  to avoid that new PQ21 and PC60  short again and at the same time that might fix +3VALWP +5VALWP fail. I guess PL5 point 2 must be traced further ?

Thank you for support.

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  • Автор: freeqwer
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:|
Little resistance
I think the value there must be in kom

To remove PQ22 .
To measure

If does not help, then remove PU6.
To measure

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