Acer Aspire 5750-6845 dead

[tibimakai]

Last night, I have picked up this laptop and it's my first laptop that I will try to repair to component level.
It seems dead, no LEDs, power adapter is good, MB gets the 19V.
I see a mangled USB port, which is on a separate small board.
Not sure where to start?
When I'll get home, I will look for the MB part number and I will take some pictures and post them here.
Any other input on what should I check?
Any help would be appreciated.
Usually I'm dealing with LCD TVs and monitors, but sometimes I pick up some laptops too, but this is the first time that it really needs some repair.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

MB markings are:
P5WE0 LA6901P
REV 2.0
Anybody has a schematic for this model laptop?

[fddizon]

Re: Acer Aspire 5750-6845 dead

here it is bro

[tibimakai]

Re: Acer Aspire 5750-6845 dead

Thank you for the schematics!!
It looks scary for somebody who is looking for the first time at a laptop schematics.
Any pointers where should I check first?

[tibimakai]

Re: Acer Aspire 5750-6845 dead

I have took some pictures:

[tibimakai]

Re: Acer Aspire 5750-6845 dead

A simple stupid question, when measuring voltages in the charging circuitry, the laptop has to be turned on with the button?
What voltage should I have at BATT+?

[speedypro]

Re: Acer Aspire 5750-6845 dead

I see a mangled USB port, which is on a separate small board.

Disconnect that board. A faulty USB port/socket will sure prevents a laptop to show sign of life.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

It's not connected any more.
I'm working with an empty board, only the fan and the CPU is installed.

[Techie666]

Re: Acer Aspire 5750-6845 dead

Thank you for the schematics!!
It looks scary for somebody who is looking for the first time at a laptop schematics.
Any pointers where should I check first?

Hey there, just my 2cents

Look at the voltage rails in page 3 in the schematic

first thing you need to make sure is that you have the always on voltages.
you can find out what they are looking at the S5 column
the rest of the voltages (S1 voltajes) should appear after you push the power button.

good luck with your first laptop repair, we'll try to guide you along the way, just keep posting your findings.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

Thank you, I will check that too.
I have done some measurements at the charging IC and there are two FET transitors PQ15 and PG16 and at the PQ 15 I have 19V, but at the output toward the PQ16 I have only 0.7V.

[Techie666]

Re: Acer Aspire 5750-6845 dead

A simple stupid question, when measuring voltages in the charging circuitry, the laptop has to be turned on with the button?
What voltage should I have at BATT+?

Laptop doesn't need to be powered on, charging circuit works all the time

if battery is installed BATT+ will have as much voltaje as the battery is providing at the moment, fully charged 12.6v, if not charged will show less. without the battery, you should read 0V on BATT+

First you are looking for VIN (adapter power) past PL1 (page46), then you should check and make sure you have B+ (main power) (PL22 page 47) if any is not present check for shorted or damaged components. start with PQ6, PQ7 then move on to PU1.

[Techie666]

Re: Acer Aspire 5750-6845 dead

Thank you, I will check that too.
I have done some measurements at the charging IC and there are two FET transitors PQ15 and PG16 and at the PQ 15 I have 19V, but at the output toward the PQ16 I have only 0.7V.

that means you have main power B+, batt+ will have power when battery is connected. if you connect the battery, do you see a charging light? test PQ16 pins 123 with battery in.
post your exact measurements and the testing point.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

I will have to try, but before I took the laptop apart, there were no lights with battery plugged in. I'm at work right now.
I have found a broken USB port, maybe that blew up a component.

[Techie666]

Re: Acer Aspire 5750-6845 dead

I will have to try, but before I took the laptop apart, there were no lights with battery plugged in. I'm at work right now.
I have found a broken USB port, maybe that blew up a component.

I'm not sure what lights are available in this model, no big deal right now until you are in front of the laptop.

As speedypro sugested keep the usb board off until the rest is working.

The usb problem may have shorted the +5VALW rail, which could have damaged PU2 or u46 or components around those ICs.



post your findings around these areas, I'll help when I can.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

Thank you very much for helping me. I appreciate it a lot.
First, it was scary to look at this board, now since I'm keep measuring and finding all the components on the board, after looking at the schematics, it begins to look much less challenging, then the first time I have look at this board.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

that means you have main power B+, batt+ will have power when battery is connected. if you connect the battery, do you see a charging light? test PQ16 pins 123 with battery in.
post your exact measurements and the testing point.

With the battery installed, at pins 1,2,3,4 I have 0V. At pins 5,6,7,8, I have 11.11V.

The damaged USB port, is a separate mini PCB board, with a ribbon cable which is not installed.

None of the LEDs are lit up, on or off.

[tibimakai]

Re: Acer Aspire 5750-6845 dead

At PU2, I'm measuring the inductor PL5(output from the IC) and there is 0V, so it looks like, I don't have +5V there.
The IC is bad and needs replacing?

[tibimakai]

Re: Acer Aspire 5750-6845 dead

I don't have 3V at pin #11 and the same thing goes for 5V at pin #20.
I can measure other voltages at the chip. 2V reference voltage is there, there are other voltages there, like 4.5V, 3.1V.
This means that PU2 has to be replaced?

[tibimakai]

Re: Acer Aspire 5750-6845 dead

Anybody? I could use some help here.

[whaldsz]

Re: Acer Aspire 5750-6845 dead

What do you get at EN pin13? VREG3, VREG 5 should be 3.3V, 5V when pin13 is high.