Aspire 7740

[JJR]

Hi all, I've got a clients Acer Aspire 7740 Laptop that wont boot, black screen, fan not spinning, nothing.

2 months ago I replaced his hard drive, re-installed Win 7 and supplied a new Delta charger. All was good.

At first I thought 'duff charger' but no, it tests fine 19.23v and works on another Acer.

Ok, duff HDD, no tests fine.

Must be the DC jack, no tests fine, I'm getting power to the battery connections, 3.33v on 3 pins.

Replaced RAM, removed WLAN and so on.

I've given the mobo a good eyeball inspection, it looks perfect.

And I'm now stuck, I've got the schematic but I'm pretty clueless at this stuff. I have replaced loads of DC jacks, USB ports and audio jacks but thats about my limit.

So, can any of you good guys be of assistance? If I can't get it going I will refund the guy for the charger & HDD, but I'd rather fix it for him.

Cheers in advance

Dave

[meritosari]

Re: Aspire 7740

i think you should try flashing BIOS chips first, good luck

[lefos]

Re: Aspire 7740

Try powering it on without keyboard and touchpad. They might have been damaged from liquid. This one has only intel's gpu right?

[JJR]

Re: Aspire 7740

meritosari: I have never flashed a bios on an unresponsive board but I will look into it.

lefos: Yes it is Intel & yes I tried disconnecting everything.

Thanks Guys

Dave

[loser18]

Re: Aspire 7740

what voltages are You getting on U19A (SIO)-pin 99 before & after pressing power button?

[JJR]

Re: Aspire 7740

Hi loser18, the laptop is at work, I will check when I get back on Monday.

Cheers
Dave

[dj_ricoh]

Re: Aspire 7740

the thermal compound was good?

if it was hard then you have to reflow the bastard.

[JJR]

Re: Aspire 7740

dj_ricoh: Hi, Thermal compound was good, changed it anyway.

loser18: Showing my numptiness now, cannot find U19a on the mb, here is a pic of U19, don't know 1 pin from another any help appreciated.

Dave

PS. It really is about time that I knuckled down and learned this stuff!

[JJR]

Re: Aspire 7740

I am getting 3.33v to PWR_SW1 & I get 0v when I press the button.

[cyberhack]

Re: Aspire 7740

Here is pin 1
Also you can always download the data sheet on the chips good place to start.

[JJR]

Re: Aspire 7740

Thanks cyberhack, so counting anti-clockwise pin 99 should be 3rd from left, bottom row.

If I am correct I'm getting 0v.

Dave

[loser18]

Re: Aspire 7740

I'm terribly sorry...
Told You to check wrong PIN...

Right is PIN95 (check voltage before & after pressing PWR button)
Also check voltages of PIN102, 19, 46, 76, 88, 115 & 104 (all of these should have 3V before pressing anything)...

Next thing I would check is U82:

PIN16
PIN8
PIN17

& then voltages of all big coils after pressing PWR button...

[dj_ricoh]

Re: Aspire 7740

hmm! i`ll say lets start with basics !

i3-330M ? if yes then test with another one.
(what you never saw a i3 dead? wanna see my stash)

this cpu its with Intel® HD Graphics

[loser18]

Re: Aspire 7740

Of course, before any measurements you need to visually inspect whole mobo under microscope & try another CPU & RAM...
If it doesn't post, but turns on, check voltages & resistance @ all big coils...
He said that fan is not spinning at all, so if the CPU would be the case it would spin the fan at least for a sec...
Just my opinion...

[dj_ricoh]

Re: Aspire 7740

yes and no!

yes it should if it powers but no because its dead short? no feed back.

check the coils and AANNNND take the CPU out and see coils like that

[JJR]

Re: Aspire 7740

loser18 : Haha, no worries mate, I'll follow your instructions in the morning.

dj_ricoh : Yes, normally I would have tried another cpu but I've nothing suitable to swap it with at the mo.

Dave

[JJR]

Re: Aspire 7740

Sorry guys, you were posting as I was composing

I don't have a microscope but I do have reading glasses & a magnifying glass

[loser18]

Re: Aspire 7740

In almost every 2nd i3/5/7 mobos I'm getting (which doesn't want to turn on-no fan spins) basically stuck in S5 state, is the SIO/KBC faulty...That's why I told him to check that one first...
Battery connector is getting voltages, so assume the charging rails would be OK...
I'm talking about KB3930 & 3926, they're really crap however this one have nuvoton & was never reworking that one...

[JJR]

Re: Aspire 7740

Hi, OK got some testing done this morning, results as follows:

U19
Pins 19, 46, 76, 88, 104, 115 all 3.3v before & after pressing power button
Pin 95 3.3v & 0v

U82
Pin 8 0v & 0V
Pin 16 19v & 19v
Pin 17 0v & 0v

Coils
L13 0.83v & 0.83v
L18, L21, L26, L28, L34 all 0v & 0v

Dave

[loser18]

Re: Aspire 7740

Are You sure about pin8 @ U82???
(You can check the voltage also @ R297 or C731)

There must be 3.3V as it powers SIO/KBC and You've said that You got 3.3V on all PINS...
Looks like it's stuck in S5 state...
Could you also post resistance of all coils?