Acer 5742G power problem

[rtstorm]

Hi, i need help with acer 5742G (it is Compal NEW71 LA-5893P)

Laptop wont start when connected LVDS. When i disconnect LVDS fan start spin, no picture on VGA output.

I found that i hava 0.94V on PQ36 and PQ35. and i have 4 Ohm D to S
I check PQ36 and PQ35 them they have no leakage

[rtstorm]

Re: Acer 5742G power problem

i check PU998

[khaahk]

Re: Acer 5742G power problem

Try a working panel. Measure resistance of lvds connector power lines, pin 1-7.

[rtstorm]

Re: Acer 5742G power problem

You mean to plug in the LCD check resistance 1-7 pin

[khaahk]

Re: Acer 5742G power problem

With panel attached, 1-7 pin relative to ground. Panel might be shorted or LVDS cable might be shorted.

[rtstorm]

Re: Acer 5742G power problem

pin 1,2,3,4 = 25 Mohm and falling
pin 5,6 = 2.2kohm
pin 7 = 10 ohm

[rtstorm]

Re: Acer 5742G power problem

if the LCD is bad, laptop shoud work on external VGA port. But i have no picture on it

[rtstorm]

Re: Acer 5742G power problem

can you tell me what mean VGA@ xxx i cannot find the cap and resistor

[khaahk]

Re: Acer 5742G power problem

10 ohm is too small. 3V on 10 ohm, meaning it should consume 300mA. Why no picture - maybe it will not show to vga by default, maybe gpu problems. Try another panel first.

[rtstorm]

Re: Acer 5742G power problem

i try with another panel, and laptop turn on. Still no picture.

Ok now we know that panel is fail. Shoud i try reflow GPU

[khaahk]

Re: Acer 5742G power problem

I would attach POST card to see where the boot process stops. It is unlikely that reflow will fix the problem.

[rtstorm]

Re: Acer 5742G power problem

i do not have POST card, never used it. i will replace PU998 and se will that help

[khaahk]

Re: Acer 5742G power problem

PU998 output is 0.96V, should be ok for vga core. If possible reprogram ec and bios.

[rtstorm]

Re: Acer 5742G power problem

ec?

[khaahk]

Re: Acer 5742G power problem

U31 - ec bios. In bios download file there is DOS directory with file KBCA230A.rom.

[rtstorm]

Re: Acer 5742G power problem

found it, now i just need to find universal programator

[rtstorm]

Re: Acer 5742G power problem

i reflash the BIOS, still the same issue