Acer Aspire 5538 Series (Compal LA-5401p Rev 1.0) only led not start

Hi i have Acer Aspire 5538 series Laptop
that led and fan is spinning but not starting.




These are the Coils Resistances
pl4 89Ω
pl5 1 KΩ
pl8 380 Ω
pl14 90 Ω
pl7 8.3 Ω
pl6 0 Ω <--- when i take off CPU this goes Infinite
pl13 7 Ω
pl10 2.4 Ω
pl11 2.4 Ω

VOltages:

pl4 3.3V
pl5 5V
pl6 1.85V (only if i desolder PJ4 else 0V)

p7 0V ( pu6 1.1V_EN 24 0V) 1.1v is not being enabled.
pl8 1.2V
pl10 0v
pl11 0V
pl13 0V

pu6
11 3.3V

pu5
17 5V
8 3.3V
16 18.5V
13 3.3V
24 5.2V
3,4 2V

Heat up diagnostically north bridge.

1.1V_EN is not being sent so i must follow this signal backwards

does anyone have the power up sequence for this?

I don't have a power sequence for this mobo.

Course of the signal, which switches power on for +NB_CORE.

U22 (pin 8) -> R232 (0Ω) -> PU6 (pin 24)
or if you don't have U22:
U20 KBC (pin 99) -> R228(0Ω) -> PU6 (pin 24).

Try to circiuito short of PL6
viewtopic.php&f=232&t=986

Ok after many chips and tranzistors replacement and burned CPU now i have All voltages on all Coils
pl4 3.3v
pl5 5v
pl8 1.2V
pl14 1.5V
pl7 1.03V
pl6 1.85V
pl13 0.9V
pl10 1.1V
pl11 1.1V

but it doesn't open i suppose it also burned other Sb/ NB /Graphics
i reflowed graphics but still nothing.

Resonators..
X1 WORKING
Y1 WORKING
Y4 WORKING
Y3 WORKING
all checked with Osciloscope
any signals i should check?

Reprogram BIOS.

U3 is getting really hot quickly as i open the power.

If it was bios it wouldn't open at states at all. is it?
i have a debug card and it doesn't start Posting at all.

-- 30 June 2014, 22:24 --

Ok reflashed Bios
the original dump was the same as the
one dowloaded from acer...
still nothing..
i suppose its Southbridge or Graphics.
how can i check now what it is?

On this mobo you must use this debug card (schematic):



Your debug connector:

If very hot U3 is probably bad.

when i put another bios on, the led turned orange when i plug in the adapter.
and when i press on its orang and blue together.
but before it was green only when i pushed power btn
did i put wrong bios and it is orange now ? or it is normal behaviour?

Measure the voltage on pin 13 of U20

u20
13 is 0 at adapter in and when i press power btn
it gows up but i dont know how much up because i am metering it with multimeter.
and then it gows down to 0 again.

In general
when adapter in orange led is on.

when i power on
blue and orange led opens.
then fan opens
then fan spin down for a while then spins up again and then shuts down and only orange led is open.

I think it is the fault U3

ok i will change it with another one.

This chip has Heating cooling pipe on so maybe it should be hot or no?
but it gets too hot in too short.
more than cpu.

Warms up a little but not immediately.

Right now it dont have RS780
but i have RS780MN

can i replace or not?

the one says 216-0674026 <-RS780
and other 215-0674034 <-RS780MN

The diagram shows the ATI RS780M and RS780MN.
The compatibility can not help you.
Wait for someone who has tried the replacement

Hi ,

Have You tried to replace this chips ? result ?

Thx

No i didn't replace it
i am afraid it wont work.
i actually found one of the same but i destroyed 4 pads
so i will probably buy it to test it but next month.