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Old 01-28-2016, 05:33 PM   #1
kriss2008
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Post Acer Aspire 5551 no power

As this is my first Thread I would like to welcome everyone and apologize for my English.
I have my testing laptop Acer Aspire 5551 with motherboard NEW55 LA-5912P Rev: 1.0.
Short story of this laptop. Laptop worked fine till I wanted add some ram and did not want to power up. After diagnosing I reprogrammed bios and found out that PQ31 had strange measurement outcome so I replaced and luckily laptop came back to life. There were still defects like there was no battery charging, U70 got very hot and laptop turned off after a while.
To make things worse, by mistake I made short in the charger PU5. Now laptop does not give any sign of life.
I made measurements on the B+ rail.
Given voltage from power supply: VIN 19V
Current uptake in ST-BY: 0V
No volt. on main coils 3V\5V PL3 \ PL4.
Resistance to ground: PL4( 50 i 30 KΩ i PL3 (1.6Ω)
PL1- 19V
PU1 (LM393):
leg.1 – (PACIN) 1OUT, 3.13V
leg.2—RTCVREF, IN-, 3.28V
leg.3—VIN, IN+, 3.60V
leg.4 - gnd
leg.8- VS vcc, 18.30V

PD1 Zener diode: K 3.13v, A 0V
PD2: K 18.35V A 18.98V
PQ1 : (TP0610K): D 18.32 V, S 17.80V, G 17.63V
PU2: (GT920 T24):
Vin 17.80V
Vout 3.28V
PU3:
Vcc 0V , rez 53KΩ
PQ3: Dren Line B+ 0V ,PR34 0V
I will be very grateful for any suggestions on where to make measurement and what value I should expect to locate the culprit.
Attached Files
File Type: pdf compal-la-5912p-r1-schematics.pdf (692.5 KB, 79 views)
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Old 01-29-2016, 06:48 AM   #2
kriss2008
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Default Re: Acer Aspire 5551 no power

Anybody have any suggestions where to start ?
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Old 01-29-2016, 08:51 AM   #3
alihomee
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Default Re: Acer Aspire 5551 no power

try check battery connector if got any voltage
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Old 01-29-2016, 11:44 AM   #4
meritosari
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Default Re: Acer Aspire 5551 no power

Quote:
Originally Posted by kriss2008 View Post
No volt. on main coils 3V\5V PL3 \ PL4.
Resistance to ground: PL4( 50 i 30 KΩ i PL3 (1.6Ω)
- You have a little short at +3valwp
- Try remove U70 first, then measure again PL3
- Or you can isolate low resistance on PL3 by removing PJ1
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Old 01-30-2016, 04:42 AM   #5
kriss2008
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Default Re: Acer Aspire 5551 no power

Much appreciate your help! As soon I do as you suggested I come back with the outcome.
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Old 01-30-2016, 01:56 PM   #6
kriss2008
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Default Re: Acer Aspire 5551 no power

Not good news

Removed PJ1 and did short-test , KBC got hot in 2.2V. Also, by supplying vin 19V PQ31 got hot so I removed from the circuit.

I have a feeling that it will be a big challenge to make this board working but at least I can learn a lot.
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Old 01-31-2016, 09:36 AM   #7
kriss2008
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Default Re: Acer Aspire 5551 no power

I found short on PL26 and PQ3 \ PQ17. After exchanging short gone in this branch.
Current values with supply 19v on PL26:
Current intake: 0v
PQ5 : 19V on Drain 1.10v
PU4 l.8 VIN 0v
PQ55 – shorts G to S.
PL1 19V PL2 0V 1.6 M Ω
Pd17 C 18.33v A 14.85v
PD13 A19V C19V
PD3 C17.82V A 0V
PD1 C3.18V A0V
PD2 C18.38V A19V
PJ23 19V
PL15 19V
PQ31 – replaced.
Values on +3VALW:
Short on PJ1 in direction to EC ENE U26 (getting hot).
Values on U26:
VCC leg.9,22,33,96,111,126 -- 02.1 Ω
AVCC leg.67 02.3 Ω
ACIN leg,127 –55.2 Ω
SPICS leg.128-- 08 Ω
Coil L84 02.3 Ω

Could anyone advice if U26 is definitely for exchange or it can be something on the way?

Could anyone advice how to remove smd coils not damaging them as I did.
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Old 11-17-2020, 09:35 AM   #8
Chieftain
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Default Re: Acer Aspire 5551 no power

PQ14 (4407A) is your problem... Change it and it will power up just fine
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