HP 15 LA- A994P no Backlight and picture !

[lapfix]

HP 15 LA- A994P Turn on without Backlight and picture , but everything is displayed normally on the external monitor.
Changing Screen and flexible same issue.

JLVDS1
Pin 1/2 = +LCDVDD = 0v
Pin 23 = DISPOFF# = 0v
Pin 24 = INVTPWM = 0v
Pin 27/28 = INVPWR_B+ = 19v
Pin 32/33 = +3VS=3 .42v

UG1 don't exist , so + lcdvdd is taken from RTD2132S itself pin 15 = +DP_ENVDD = 3.45v.

No component from Pin 15 until pin 1/2 JLVDS !

What to check else friends !..thank you .

[peste]

Re: HP 15 LA- A994P no Backlight and picture !

HP 15 LA- A994P Turn on without Backlight and picture , but everything is displayed normally on the external monitor.
Changing Screen and flexible same issue.

JLVDS1
Pin 1/2 = +LCDVDD = 0v
Pin 23 = DISPOFF# = 0v
Pin 24 = INVTPWM = 0v
Pin 27/28 = INVPWR_B+ = 19v
Pin 32/33 = +3VS=3 .42v

UG1 don't exist , so + lcdvdd is taken from RTD2132S itself pin 15 = +DP_ENVDD = 3.45v.

No component from Pin 15 until pin 1/2 JLVDS !

What to check else friends !..thank you .

check the route between RTD2132S and the LVDS cable socket so that it is not interrupted.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

Thank you my friend.

I can't find any continuity between pin 15 of UT1 and any other components
Maybe a boarderview can help to trace it !..don't have.

At page 16 there's a Resistance = RT9 with @..but even have @ and is present at the motherboard..

[Sametbey]

Re: HP 15 LA- A994P no Backlight and picture !

When you look at the block diagram, RTD2132S provides the connection between the processor and the LCD panel. 3 4 pins of JVDS socket LCD panel data connection. To detect when the LCD panel is installed. If you have an oscilloscope, you can check the input signals. You can try bios pgm first.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

Thank you Sametbey.
Don't have oscilloscope for the moment...about bios i think when there's display at external so no need for flashing bios !! am i right !

[peste]

Re: HP 15 LA- A994P no Backlight and picture !

Thank you Sametbey.
Don't have oscilloscope for the moment...about bios i think when there's display at external so no need for flashing bios !! am i right !

you don't need bios ...

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

@lapfix, i Know UG1 dont exist on the board but can u measure voltage on PIN5/3/1 of UG1 pads.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

THank you mcplslg.

Pin 1 = 25mv
Pin 3 = 26mv
Pin 5 = 3.3v

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

So Enable is missing. You can try shorting pin5 & pin1 and see if there is display. However, do check resistance on pin1 before shorting.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

mcplslg thank you again.
So strange this motherboard ..so before shorting pin 1/5 i check pin 1 resistance , finding 32 Kohm so it's OK , but i try in diode mode that i always work with it ( diode mode ) ..finding 0.524v at pin 1 so all is ok...now try with screen and ready to short the 2 pins..and a surprise there's a display before shorting!!..all is OK !..measure UG1 pin 3 and there's 3v enable ...maybe the pulse of diode mode voltage do something !

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

Update :
After assembling the lap..same issue no display...try another flexible /screen : sometimes it work and other no.

when working it's not stable , sometimes i got backlight and picture...sometimes no

i order a third flexible to confirm !

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

I dont think 2 flex cable will be bad. Issue seems to be related to mb. Have u tried jumpering pin5 & pin1 when there is no display on internal screen??

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

i try , there's a backlight but no picture

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

Hmm... I doubt it may be SOC . Do you have bga machine??

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

No my friend , maybe try to make a brief heating , if not i have nothing else to try...thank you for all your support

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

I'm afraid heating with blower may damage the soc. Bga machine is a must to heat soc .But since you dont have a bga machine, dont heat the soc on top with a blower. Instead heat it a bit on back side and see if there is display.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

Hello my friend...that's how heat it , from back side a little but no result.

Strange thing : i try another dump from here and backlight is OK , but no picture !

[mcplslg123]

Re: HP 15 LA- A994P no Backlight and picture !

Somewhat similar fate to your earlier post of LA-E791/802P. You really cant do much with newer mb's as mb components are not labelled and very often SOC's fail. Schematic/boardview are available only on paid sites making the whole repair unviable. We cant help it but has to cope with it.

[lapfix]

Re: HP 15 LA- A994P no Backlight and picture !

Again , thank you for all your advices , yes you are right .