Acer Aspire 5740g dead (no power - no lights)

[pctek]

I have an Acer Aspire 5740g with no power - no lights . Adapter is tested ok , motherboard is getting power 19V from power jack . I've found some mosfets getting 19V also and one with 3.3V but nothing else (nowhere 5V , or 1.1V) .Also , I can see 3.3V on the power button but nothing on LEDs . Any help please where to look ?

[xose_maria]

Re: Acer Aspire 5740g dead (no power - no lights)

Hi. I am notebook electronic technician. I can not speak English but but I can give a few tips for laptop repair.

Always or almost always connected to the charger will present two voltages 3,3V and 5V. This power supply will feed the rest of internal power supplies (VGA, CPUCORE, etc).

You do not give many details but I think your motherboard is Wistron JV50-CP.

Download schematic here: http://www.mediafire.com/view/?33hk7d29msca88y

I begin with the charging circuit (p. 51). If this circuit does not work you will never have the rest of voltages. Whenever you have the appropriate schema, you can walk you through the data sheet of the integrated circuit (eg ISL88731A).

You'll have to have a minimal knowledge of electronics and know how to operate the integrated circuits in the power of laptops.

For downloading schematics circuits: http://www.notebookreparos.com.br/no...bo-schematics/

In this forum (mine) also have a lot of information but is in Spanish. http://www.reballing.es

In conclusion, before you start repairing laptops you need to know who is the real manufacturer of the product. The situation now was such that the trade brand name and manufacturer are different concepts (with rare exceptions). Therefore, try to determine who is who and how to find the schematic diagram for a specific laptop.
The bulk of laptops are made in China and Taiwan manufacturers such as manufacturers Quanta, Compal, Asus, Pegatron (a subsidiary of Asus), Inventec, Wistron, Foxconn, Uniwill (now included in the ECS), ECS, Mitac, Clevo and others, only Samsung is in Korea.Now look for any brand which manufacturer produces motherboards:

Acer - Quanta, Inventec, Compal, Wistron.
BenQ - Quanta.
Dell - Quanta, Compal, Wistron, Samsung.
Fujitsu-Siemens - Uniwill, Inventec.
HP - Quanta, Inventec, Compal, Wistron.
Lenovo - Quanta, Compal, Wistron.
Packard Bell - Quanta.
Sony - Foxconn, Quanta.
Toshiba - Quanta, Compal, Inventec, Asus.

More info: http://www.laptopdesktopschematic.com/

I can not help more. My native language is Spanish. Sorry, forgive my English

Good luck with the repair

[Hosm]

Re: Acer Aspire 5740g dead (no power - no lights)

Hallo,
I have the same problem, i also test the charge controller and the battery charged without any problems.
Please could you help me to solve this problem.

[bliu2002]

Re: Acer Aspire 5740g dead (no power - no lights)

My Acer 5740g has the same problem. I measured the DCIN1, it got 19V; but none of the LEDs lit. Thanks xose_mania, I downloaded the schematics, it is helpful, but does not seem to match my motherboard because I could not find the components I was interested in. I have attached the image of the board, could someone verify whether I have the correct schematics? If not, where can I find them? Thanks!

[lord]

Re: Acer Aspire 5740g dead (no power - no lights)

xose maria put link to laptop schematics site where you can search and find the right scheme for your device.
Good luck!

[bliu2002]

Re: Acer Aspire 5740g dead (no power - no lights)

Thanks! The schematics were actually the correct ones. I was able to trace down to TPS51123 the power regulator, it got 19V input but no 5/3.3V outputs, can I assume this part is dead? Are there any other possibilities that could cause it not to generate outputs?

[lucco85]

Re: Acer Aspire 5740g dead (no power - no lights)

Yes,first check on pin 13 if you have enable signal.
If you have,open G151 and G129 then check pin 8(3V) and pin 17(5V)
Check mosfets(u73,u67,u74,u69)

[bliu2002]

Re: Acer Aspire 5740g dead (no power - no lights)

Pin 13 is 5V, pin 8 is 3V, pin 17 is 5V, but pin 18 is 0. Traced S5_ENABLE to Q18, and found 1D05V_VTT is 0. Any idea? Am I on the right track?

Thanks!

[lord]

Re: Acer Aspire 5740g dead (no power - no lights)

Check mosfets(u73,u67,u74,u69)

[bliu2002]

Re: Acer Aspire 5740g dead (no power - no lights)

I cut the wire between pin 18 and S5_ENABLE, and shorted the pin 17 and 18, so that ENC is 5V also, then got 3.3V and 5V outputs from U72! However, the S5_ENABLE is still low, and none of the LED lit up. Sounds like not only S5_ENABLE is a problem, there are other issues in the rest of the system, any insights? Thanks!

[xray303]

Re: Acer Aspire 5740g dead (no power - no lights)

Hi,

Thanks for the schematics. Someone asked me if i could repair his 5740g.
The prob was :
Was working fine with battery but the charger didn't work, when you plug it in, the power adapter led is not illuminated anymore. Quick check with a multimeter and the DCIN of the laptop was in short circuit. (he tell me that he try to power the laptop with a wrong adapter before he got this prob)

After some research in the schematics i suspected D10 (protection Diode), removed it and now it's working again.

Just posting that because it is a similar issue, but not exactly the same one, but it could help someone .

Regards,

[bliu2002]

Re: Acer Aspire 5740g dead (no power - no lights)

I have got the laptop fixed after replaced U72 and re-programmed BIOS (U16).

[Tuomo]

Re: Acer Aspire 5740g dead (no power - no lights)

I cut the wire between pin 18 and S5_ENABLE, and shorted the pin 17 and 18, so that ENC is 5V also, then got 3.3V and 5V outputs from U72! However, the S5_ENABLE is still low, and none of the LED lit up. Sounds like not only S5_ENABLE is a problem, there are other issues in the rest of the system, any insights? Thanks!

This chip look works normal, so test U15 which enable S5.

First test U15A PIN 95 = 3.3V, wnen press powerbutton is should go 0V and back to 3.3V.

[danea]

Re: Acer Aspire 5740g dead (no power - no lights)

I have the same problema with the same laptop.waiting for a bios programmer.i learn a lot from all of you.The schematic help me a lot to understand what kind of problem i deal with.Hope it will be a positive final.

[danea]

Re: Acer Aspire 5740g dead (no power - no lights)

Thanks.

[vinkos]

Re: Acer Aspire 5740g dead (no power - no lights)

I have got the laptop fixed after replaced U72 and re-programmed BIOS (U16).

I did change mosfet Q38 to fix my laptop!

[alihomee]

Re: Acer Aspire 5740g dead (no power - no lights)

this model mostly got cmos and bios problem. take out the coms and then check if cant then try with flashing bios but first check that voltages present at bios chip are not....

[danea]

Re: Acer Aspire 5740g dead (no power - no lights)

still got no power in this motherboard.re-programming the bios does not solved the problem.

[oxonater]

Re: Acer Aspire 5740g dead (no power - no lights)

Hi anyone know where I can get a schematic for an e system 4125c the board is a uniwill
L55II9. This board works ok on battery but nothing when ac adapter plugged in thanks in advance.

[spleenharvester]

Re: Acer Aspire 5740g dead (no power - no lights)

Doesn't appear to have been released matey. You're best off starting your own thread btw.