ASUS X58L NO Display Strange Fault

[loser18]

Hello there...

I've got an ASUS X58L mobo ( 08G2005XB21G )...

It came to me shorty, but found it was causing by DC jack...
After took it off had all power voltages fluctating, no fan spin, only "wifi" & "zz" LEDs lit...
Suspected north (U1101) so reballed...
Now it turns on with "zz" LED, fan spins & stays like that...
Have absolutely NO output to LCD or External...
So checked J4601 voltages & found that has no voltage on +3VS_LCD...
As far as I understand the schematics, it's coming from Q4602...
There's no voltage present on PIN3 & PIN4...
It's a N-channel FET, so there should come 12V to gate to enable the +3VS_LCD???

Am I right???

BTW I've checked R4601 & have 12V on one side but nothing is coming from the other (PIN1)
Also reads 1mega as it should...

Could You anyone explain me that +12VS???
Any help would be appreciated...


Also attaching Q4602 datasheet & schematics (again says X51L model, but I've got the same marking on my mobo & looks it's the same)

[loser18]

Re: ASUS X58L NO Display Strange Fault

Forgot to mention that I've been mesuring voltages of J4601 (LCD connector) without LCD or LCD cable connected...

[loser18]

Re: ASUS X58L NO Display Strange Fault

Also found that that Q4604 is missing, but think it's due to a design revision...

[khaahk]

Re: ASUS X58L NO Display Strange Fault

Q4601 has 3V at gate, so it pulls the other side of R4601 to GND, hence no voltage at Q4602 gate. The LCD gets power when 965GM turns on L_VDD_EN. Why did you suspect the GM when power was fluctuating?
If have spare, try to change the 965. If you have post card, use it - maybe get some useful info.

[loser18]

Re: ASUS X58L NO Display Strange Fault

THX for response...

I suspected GMCH, cause it's been getting hot when DC connected & WIFI LED has been solid...
So thought WLAN connector didn't get PLT_RST# voltage...
Also L8201 has been reading only 12Ohms, but after reball is the same...
I've heard that in some cases, even if the coil near the GMHC, CPU socket (if CPU present) or GPU shows low resistance it's normal & tried it on some working mobos & ussually measuring around 12-15 Ohms @ coils...

COULD ANYONE CONFIRM THIS???


Looks I'm learning the hard way, lol...maybe there was absolutely no need to reball GMCH...

SO,

Checked Q4603 @ PIN1 & getting 0V...
Now assuming that North is not generating L_VDD_EN...

BUT THE WEIRD THING...

Just took a DELL D520 (Quanta DM5) mobo...fully working, to compare voltages at LVDS circuit (looks pretty the same design)
Guess what...
With LCD cable disconnected I'm also getting NO L_VDD_EN Voltage...(0V)
However when I connect LCD Panel the voltage comes up with display...

Only thing I've noticed that VDD EN voltage comes through N channel MOSFET on ASUS mobo, but on DELL it's coming through NPN transistor(does this mean it's a P channel fet???)

PLS, COULD ANYONE CLEAR THESE THINGS FOR ME, AS I'M GETTING CONFUSED MORE & MORE

[loser18]

Re: ASUS X58L NO Display Strange Fault

Now I've checked all the voltages across all caps @ North (U1101) & getting 1.05V, 1.2V & 1.8V...
Is there any way, how to check if the chip itself is OK?

[khaahk]

Re: ASUS X58L NO Display Strange Fault

DM5 uses similar schematics, different transistors but principal is same. There might be some test pin to see whether the LCD is connected or not. Sadly there is no way to confirm that the chip is dead. Just have to change and see. Strange is that the behaviour of the machine changed after reball.

[loser18]

Re: ASUS X58L NO Display Strange Fault

Will try change the chip tomorrow then...
But still don't understand that DELL...
i know there's always problem with screen replacement compatibility, so maybe it's checking screen specs somehow and release voltage after?

[loser18]

Re: ASUS X58L NO Display Strange Fault

OK...

I've read another thread about LVDS signal...
Can I inject 3V to Q4602 gate or desolder & short its drain & source to check if it's everything else ok???

I know the mobo is not worth fiddling around, but I want to understand every circuit...

[atsio]

Re: ASUS X58L NO Display Strange Fault

Just a wire from source to drain. On DM5 you can see on pin 13 of LVDS connector the signal LCD_TST which is connected to Southbridge and probably if you dig a little bit further on the datasheets of the IC's you'll find the links to the ENVDD signal.

[loser18]

Re: ASUS X58L NO Display Strange Fault

Just a wire from source to drain. On DM5 you can see on pin 13 of LVDS connector the signal LCD_TST which is connected to Southbridge and probably if you dig a little bit further on the datasheets of the IC's you'll find the links to the ENVDD signal.

Shorted Source & Drain...
Definitely something happens as screen goes black after pressing pwr...
However no light & no image on screen (checked under light)

[atsio]

Re: ASUS X58L NO Display Strange Fault

Remove cpu and measure voltage in holes C1 and D6.

[loser18]

Re: ASUS X58L NO Display Strange Fault

Remove cpu and measure voltage in holes C1 and D6.

Hi atsio...

I'm getting:

C1=1.05V
D6= 1.02V

Exactly...

Checked S4 & S4 @ SIO and the're OK...
Also PLTRST @ pin2 of U2101...

OH, ALL THE READINGS TAKEN AFTER REMOVED THE SHORT & RESOLDERED Q4602 BACK TO IT'S PLACE...

[atsio]

Re: ASUS X58L NO Display Strange Fault

Check voltage on pins 18 and 9 of U3001

[loser18]

Re: ASUS X58L NO Display Strange Fault

PIN 9 = 3.3V
PIN18 = This one shows me different values on different scales???

2V scale = 1.2V
20V scale = 1.9V
200V scale = 10.5V

WTF???

[atsio]

Re: ASUS X58L NO Display Strange Fault

Have you flashed the bios?

[loser18]

Re: ASUS X58L NO Display Strange Fault

It's 48-pin TSOP...

I don't have that kind of adpater...
Got only PLC & SOIC8...

[loser18]

Re: ASUS X58L NO Display Strange Fault

Is there any way to use PLC adapter & solder wires on chip pins?

[atsio]

Re: ASUS X58L NO Display Strange Fault

Solder 48 pins?

[atsio]

Re: ASUS X58L NO Display Strange Fault

There you need a post card, the type you can solder wires on the board, because the mini pcixpress does not support it.