acer 5742z dead in my hand

[Akira81]

hello

this is my first post and my enlish is not so good .. so be patience

i have an acer 5742z with a bad panel, i have found a 15.6 led to replace it and i have try it before remount the case and the cover lid... evrithing was ok so i was happy and i have turned off windows and i ve been ready to reassemble.

When i start to reasseble all, i forgot to remove the battery and when i have attacched the ribbon cable to my panel i have see a little lightning near here nothing of too bad i think....

after this (when i put in it power cord) i have a battery led blinking on first time and after orange when charing and blue after full charge but i have not power

theese are the things i do:

i have removed the power cord , the battery and keep power on for 30 seconds

i have unsoldered + pin of cmos battery for 20 minutes without power cord and battery to try a reset cmos

i have changed a battery with an other one charged

i haave disconnect the monitor wire from motherboard and connect an external monitor ....

nothing ... the notebook is dead

please help me!! what can i try ???

[samanthban]

Re: acer 5742z dead in my hand

first check voltage at u16 pin 96

[dellxps15]

Re: acer 5742z dead in my hand

5742 suffer from corruption of ec bios. when psu is plugged and charge battery, ill assume that there are no shorts in notebook.

try with ec bios and see if u have 3.3 and 5 volts. if not thy while pressing power botton if 3.3 and 5 volts comes.

[Akira81]

Re: acer 5742z dead in my hand

I have disassembly the motherboard and with battery in and power cord in i see 3,28v on pin96 of the u16

0v whitout power cord. And battery in

3,28v without battery and power cord in



Are there some testpoint to get this motherboard on without power button/ flat?

[samanthban]

Re: acer 5742z dead in my hand

then its better to do as dellxps15 before the next step

[Akira81]

Re: acer 5742z dead in my hand

I m noob i cant understand what means ec bios and where i can measure 3.3 and 5v ...

[samanthban]

Re: acer 5742z dead in my hand

you have 3.3v and check for 5v at pl47.

[Akira81]

Re: acer 5742z dead in my hand

i'm going blind to find it where is the pl47!?!?!?!


i have a new70 la5892p rev 1.0

[jeremykum]

Re: acer 5742z dead in my hand

Are you powering your laptop with a normal laptop adapter or a bench power supply?
What ampere are you getting when plug in adapter without battery?

Since you still able to charge the battery, your board 19v B+ rail should be fine.

Remove power supply, Locate PU16, I think should be RT8206B, check PL27 and PL28 whether it is grounded? If power is supplied, should give 3.3v and 5v reading.

I am referring to NEW71 schematic, I don't have on hand NEW70.

[Akira81]

Re: acer 5742z dead in my hand

Remove power supply, Locate PU16, I think should be RT8206B, check PL27 and PL28 whether it is grounded? If power is supplied, should give 3.3v and 5v reading.

PL27 and PL28 are grounded

with power cord in pl28 3.5v on both side and pl27 5v on both side

during the measure i have a very hot temperature from u16

what happened???

[jasko_jacker]

Re: acer 5742z dead in my hand

I assume that the battery led is on when you connect the power adaptor (to exclude issue on battery charge chip)
U16 is the chip that provide 3.3V and 5V to powering other component on board, EC manage many things including the power signal from the power button. In this cases , first we have to check if there are no power problems, after we have to reprogrammed the bios U30 and the EC U31.
in both cases, I recommend not to proceed if you do not have spare components (pu16 = = RT8206B RT8206A, PQ46,47,48,49 NPN power mosfet) and / or a programmer for bios chip and dell'EC
Check with the multimeter in ohms:
PL28 red probe on pin 1 and black probe on GND, same with PL27.
If there are no short circuits, connect the power adapter without the battery and the red probe to PL28 pin 1 and the black GND (multimeter in volts DC) should read around 3.3V same with PL27, but you should read 5V.
Then we check, if voltage is present on the BIOS U30 pin 8 and the memory for the EC U31 pin 8. If everything is ok then proceed to reprogram both U31 and U30 you find the files on internet.
There would be many other checks but these are the main

[jeremykum]

Re: acer 5742z dead in my hand

Beside Jasko recommendation, PL27 and 28 shouldn't be grounded without power supplied. Grounded I mean you probe either side of a PL with any screw points (negative ground). It should give you high ohm reading.

If it is grounded really, one way is to remove the RT chip, test for ground again. If now not grounded, replace the RT should solve this part of the problem.

PL is a choke, has very low ohm reading, usually about 8-10 ohms.

On the other hand u16 shouldn't be hot to touch. Solve this main power supply issue first. If you are lazy as I sometimes do, I will just replace this RT and test if it works. (since I have many on hand and it's cheap)

PL27 and PL28 are grounded

with power cord in pl28 3.5v on both side and pl27 5v on both side

during the measure i have a very hot temperature from u16

what happened???

[giove]

Re: acer 5742z dead in my hand

hi, i have similar problem on this motherboard, only that on my on PL28 on +3VALWP side i have 3,3 v but on other side i have 2,4 v. also on my motherboard i have hot temperature on u4 chip, the chipset

[giove]

Re: acer 5742z dead in my hand

please help me?

[piernov]

Re: acer 5742z dead in my hand

What is the resistance to ground on both sides of PL28? What is the resistance across PL28?
Is the PCH heating up when the computer is off (ie. no voltage on +1.05VS)?

[giove]

Re: acer 5742z dead in my hand

thank you for replay.
the resistence to ground of PL28 is 100 ohm on both sides and 1ohm across. Yes only PCH heating up when computer is off.

[piernov]

Re: acer 5742z dead in my hand

100 ohm is too low for +3VALW, and the PCH should not be heating when the computer is off. The PCH is most likely dead.

[giove]

Re: acer 5742z dead in my hand

a reflow can help?