Acer AL1721

[Gianni]

This is the first time I have an LCD display not working in my hands.

The problem is the video signal: the monitor doesn't detect the video input signal most of time, I tried fifteen times to turn it on and only twice it showed the screen, the other thirteen times it said "not signal input check the cable" and than it went in stand-by mode.
I have tested it with a different AC Adapter and the problem remains.

I opened it but I don't see any problem, all caps (Hermei and TL(?)) look good, the solder joint seems good.
There are a lot of SMT caps but I really don't know if they can be part of the problem.

ASAP I will replace all caps with Panny and I hope it solves the problem, but I would like to have your opinion.

This display is 6 years old and started with this problem last week.

By the way, the owner smokes like a chimney as you can see from the color of the rear cover.

Any comment is really appreciated.

Ciao
Gianni

[PlainBill]

Re: Acer AL1721

This is the first time I have an LCD display not working in my hands.

The problem is the video signal: the monitor doesn't detect the video input signal most of time, I tried fifteen times to turn it on and only twice it showed the screen, the other thirteen times it said "not signal input check the cable" and than it went in stand-by mode.
I have tested it with a different AC Adapter and the problem remains.

I opened it but I don't see any problem, all caps (Hermei and TL(?)) look good, the solder joint seems good.
There are a lot of SMT caps but I really don't know if they can be part of the problem.

ASAP I will replace all caps with Panny and I hope it solves the problem, but I would like to have your opinion.

This display is 6 years old and started with this problem last week.

By the way, the owner smokes like a chimney as you can see from the color of the rear cover.

Any comment is really appreciated.

Ciao
Gianni

It would be interesting to see the DC input area of the logic board. The problem may be a noisy supply for the Gemini chip, or the chip itself could be dying.

PlainBill

[Per Hansson]

Re: Acer AL1721

For what it's worth on mine it was enough to swap just one cap, but it was visibly bloated... Model no quite similar...

https://www.badcaps.net/forum/showthread.php?t=7520

[Gianni]

Re: Acer AL1721

I replaced almost all electrolytic caps, I left only a 4.7uF 50V brand TL because I had not replacement for it.
For 150uF 25V I used 150uF 16V OS-CON because they were the smallest caps I had, they were on 12V and 5V.
For 220uF and 470uF I used Panny FM.

I have cleaned connectors with a contact cleaner spray.

Now the display starts always correctly.

Here some more pics.

Ciao
Gianni

[Gianni]

Re: Acer AL1721

Today I have measured the caps I removed: only one caps was completely
ruined, it was 30.7uF instead of 220uF and it had an ESR of 6.5Ohm.

Here the values:

Logic board

Nom. Value Checked value

150uF 25V 133uF 94mOhm
150uF 25V 137uF 91mOhm
150uF 25V 136uF 91mOhm
150uF 25V 137uF 92mOhm
150uF 25V 136uF 84mOhm
470uF 16V 407uF 116mOhm
470uF 16V 397uF 113mOhm

power board

Nom. Value Checked value
150uF 25V 130uF 94mOhm
150uF 25V 132uF 98mOhm
220uF 25V 173uF 102mOhm
220uF 25V 30.7uF 6.5Ohm
470uF 16V 399uF 64mOhm

Ciao
Gianni

[mrobo]

Re: Acer AL1721

Have you solved your problem with the bad 220uF 25V 30.7uF 6.5Ohm cap ?

[houmergt]

Re: Acer AL1721

Hi, I have had similar problem with my Acer AL1722hs. When I turned on my computer on the screen was only logo Acer and Bios post for 1-2sect then backlite gone off. On the power/inverter board there were bad contacts on coils L201, L202. I resoldered them and this solved my problem.