Compaq Presario CQ70 - Display ok without backlight

[lepak06]

Hello ,

i bought an laptop Compaq Presario CQ70 .
When i bought the laptop, there a problem with the LVDS the flex burnt because a shorted . And this shorted has burnt a mosfet after DC_IN connector. I change the mosfet and the laptop work without backlight.


I tried to change LCD panel, Inverter, LVDS cable and the same problem no backlight.

I tested if i have 3VS but no 3VS on LVDS and when i check the motherboard i seen the D21 and D22 are missing. On pad ( printed trace) of D21 and D22 on the motherboard i found 3VS but not on C364 and not on C374.

I tried to jump on motherboard the lines of D21 and D22 each separately without any result.

I put 3VS directly to the inverter brighteness_con and ec_blon and the backlight work.

[fester]

Re: Compaq Presario CQ70 - Display ok without backlight

blown R222? or something on page 30 :-)

[lepak06]

Re: Compaq Presario CQ70 - Display ok without backlight

R222 is missing on motherboard

I check voltage in pads on r222 i found 0V.

it's weird that it lacks several components

[budm]

Re: Compaq Presario CQ70 - Display ok without backlight

Blank PCB can be stuffed in many ways to create a bunch of different PCBA (Printed Circuit Board Assembly) for the required PC model, so not all the parts may be on your particular PCBA.

[fester]

Re: Compaq Presario CQ70 - Display ok without backlight

look in the schematics where 3VS is created.meassure this point and if you find that 3VS is present,make jumper to lvds connector.is possible that some trace on pcb is blown.

[lepak06]

Re: Compaq Presario CQ70 - Display ok without backlight

i maked jump 3VS in D21 and D22 and shunt brighteness_con and ec_blo on inverter.
The backlight always work . When i boot the laptop the screen is White before coming the display

[fester]

Re: Compaq Presario CQ70 - Display ok without backlight

also a solution :-)