Acer Aspire 7740G dead (no power - no lights)

[F4bien]

Acer Aspire 7740G dead (no power - no lights)

My laptop shuted down while restarting Windows. Since, it is impossible to start it.

Curiously, when I plug the adapter, the is no LED ligths (Photo 2).

My adapter is OK. I tried to press POWER 1 min before plugging the adapter and press POWER but nothing happened.

I also reseted the bios removing the CMOS battery (Photo 1). Always nothing.

So, I think the problem is deeper in the motherboard.So I found the schematic (joined to this message).

I also read these two topics :

https://www.badcaps.net/forum/showthread.php?t=20475

https://www.badcaps.net/forum/showthread.php?t=41942

But the laptops are not the same as me. I am lost :/

Thank you a lot in advance for your time.

[dj_ricoh]

Re: Acer Aspire 7740G dead (no power - no lights)

check d36 and d16.

check with continuity with ground and see if they beep.

if one beeps take it out and you`re good to go

[sopik78]

Re: Acer Aspire 7740G dead (no power - no lights)

Try to flash BIOS in external programmer first and we'll see.

[F4bien]

Re: Acer Aspire 7740G dead (no power - no lights)

check d36 and d16.

check with continuity with ground and see if they beep.

if one beeps take it out and you`re good to go

Ok, it was easy to find them. Look at photo 4. Did I understand you?

One other question, what do you mean when you say "if they beep"? The multimeter will beep?

[F4bien]

Re: Acer Aspire 7740G dead (no power - no lights)

Try to flash BIOS in external programmer first and we'll see.

Do you know where I can find a good tutorial (with photos) in order to try this solution?

[dj_ricoh]

Re: Acer Aspire 7740G dead (no power - no lights)

you place the black probe on ground and red one on each side of the diodes.

if one one of them beeps on both sides the its shorted to ground.

it creates a continuity to ground and force the whole voltage to go to the ground.

does the adapter blinks or goes out?

[F4bien]

Re: Acer Aspire 7740G dead (no power - no lights)

you place the black probe on ground and red one on each side of the diodes.

if one one of them beeps on both sides the its shorted to ground.

it creates a continuity to ground and force the whole voltage to go to the ground.

does the adapter blinks or goes out?

Sorry for the time between now and your last message.

I am a bit scared. I followed your insturctions. When I placed the red probe on one side of d36 (Photo 5), i heard a small popping sound. Since, ma red probe is grilled (Photo 6).

... I was supposed to do that without power?

And now, what to do?

[User013597]

Re: Acer Aspire 7740G dead (no power - no lights)

Hello.

I think i maybe got something like the same problem:

One day i shut down my Acer 7740G (JV70-CP MB 09293-1), but after a very short time it was off. The next day i tryed to start up nothing happend...
There was no lights on when i put the charging cable (only the light at the cable was on) inside. After pressing power there was no light, no sounds, nothing (the charging cable light was still on while pressing).

Now after a long time i tryed to repair it. So i had some help and dismounted everything.

After this i was looking for the power supply socket but we could messure the 19V behind the power supply socket. There was allthough power at the charging battery cells.
After a long time i found out that i could be the U82 TPS51123. There was a problem with 5v and 3.3v because i just found some spots arround U82 with 3.3V. After i managed to get the U82 TPS51123 changed by a professional stuff. After this we checked if there is light on the mainboard if we put the charging cable into the mainboard, but there was no light on, nothing changed, after pressing power button alltough nothing. We can not find 5V or 3.3V at L35 or L36 and allthough we only found at one Testpoint arround U82 (i think it was TP59 or TP69) a volltage.

Maybe if this is important: 1 Year after i boght this notebook the DVD / Blueray player stoped working (its working on 5V). And i had some problem with the temperatur inside (maybe there is a known problem cause of this heat). But after 1-2 month checking the fan i noticed that the louver were full of dust.... But after removeing the dust the notebook was working fine like 1 year.

So now i hope you know what to do and please tell me step by step what to do.

Have a nice day.

[bajno]

Re: Acer Aspire 7740G dead (no power - no lights)

Hi everyone
My case - Acer Aspire 7740G dead (no power - no lights). There was 19V all over the board. I checked L35 and L36 - no voltage. Exchange U82 TPS51123 - no change. The board starts after flashing U21 (KBC). I got BIOS from official site.
Hope this info helps someone.

[LEPA]

Re: Acer Aspire 7740G dead (no power - no lights)

thank you i am very happy thanks bro