Acer AL2021 bricks in menu

[dondrusco]

Hi, everybody!

I have Acer AL2021 with this symptom:

When turned on, logo is bricked/unsharp (pic 1)
Display is also bad (pic 2)
I'm not able to turn off display then.

I replaced all caps in power supply, but it didn't help.
Then I replaced one 1000uF/6,3V capacitor in control unit. No change.
There is problem with voltage on micro controller, I think.
I measured voltage at 8051 controller - there were only 4,7V

Which part have I to start with to check? (pic 3)

[Krankshaft]

Re: Acer AL2021 bricks in menu

Most of the time lines and artifacts in the display are the result of a bad connection to the panel.

If you think voltage to the micro is causing it trace and disconnect that supply wire from the inverter to the main board then supply the voltage externally.

Try to get a datasheet and verify what it's supply voltage is first though.

[Toasty]

Re: Acer AL2021 bricks in menu

8051 & "family" is 5v. 4.7v is fine.

With "cut corner" of chip at TOP LEFT, Vcc is 7th pin to the right -> on top row. Ground is on bottom row, 5th pin to the right.

[Toasty]

Re: Acer AL2021 bricks in menu

On second look, the chip to the upper right in picture may be the video processor "jungle". That's a BGA chip. This problem could all be due to bad solder on that chip.

[Krankshaft]

Re: Acer AL2021 bricks in menu

If it is the BGA unless you're willing to take a chance with a heatgun to perform a ghetto reflow process then this monitor is hosed.

[EGuevarae]

Re: Acer AL2021 bricks in menu

If it is the BGA unless you're willing to take a chance with a heatgun to perform a ghetto reflow process then this monitor is hosed.

I have a similar problem with another unit (AL2120) and I have been told by the original owner that the problem was narrowed down to the BGA chip. A heatgun can really help? I've seen the same suggestion for some xbox 360 failures due to loose RAM chips. It really can help on cases like this (and teh 360 ones) ?

[dondrusco]

Re: Acer AL2021 bricks in menu

If it is the BGA unless you're willing to take a chance with a heatgun to perform a ghetto reflow process then this monitor is hosed.

OK, I try to reheat with heatgun. I have experience with reheating nVidia Geforce 7x00 Go chips in HP Pavilion dv6000/dv9000 notebooks. I try to do the same way.

[Toasty]

Re: Acer AL2021 bricks in menu

I had a Dell Latitude D800 in here a few weeks back with look-alike screen issues. Sometimes immediately, sometimes after a few minutes. Got it apart and found I could press on the video card and make it worse.

I tried this procedure for a "ghetto reflow" and the problem partially resolved. It would stay on as long as you didn't press on the board. Determined that the RAM chips (4!) also needed it done. Much too small an area to work in and would have required a very precise heat shield as many components were within 4mm of the chips. The owner procured another unit from the pile at work and I ended up just swapping the cards.

I used this procedure for a ThinkPad as a guideline and winged it from there:
http://forum.thinkpads.com/viewtopic.php?p=386104

Toast

[dondrusco]

Re: Acer AL2021 bricks in menu

Thank you, Krankshaft!

I reflow BGA memory chip - now the monitor works!

I will be more careful on the next time - 4 caps went bulged (not so much) - heat came under aluminium cover.

[dondrusco]

Re: Acer AL2021 bricks in menu

After one week of working monitor went down again.
I tried to recap, but no change.
I connected it to external power supply, with extra +5V connection, instead of 12V/5V regulator on main board. I was not able to turn it on.
When I used 12V only, I was able to turn it on.
I try to push BGA memory chip - no change. Main chip MST9251- no change.
But when I pushed microcontroller, monitor dead.
I try to reflow it - probably cold join under it.

[dondrusco]

Re: Acer AL2021 bricks in menu

Monitor is back again! I reheated all three chips. I will do more stress test on it.