820-00840 No Display

[Panrix Microelectronix]

This device came through for a 'FlexGate' repair however when we have checked the lcd connector J8500 we're missing all the EDP lines.. I've not yet come across a device with all the EDP lines missing so not sure if this is game over as the EDP_ML lines show value but the cpu is showing heat in some areas.

We have the following values in diode mode and voltage for lcd pins:

PP5V_S0SW_LCD 0.542 0v
PP3V3_S0SW_LCD 0. 541 0v

BUF_EDP_PANEL_PWR_EN 0.528
DP_INT_HPD 0.528
LCD_IRQ_L = 0.529

EDP_INT_AUX_N = 0
EDP_INT_AUX_P = 0
EDP_INT_ML_N<0> = 0
EDP_INT_ML_P<0> = 0
EDP_INT_ML_N<1> = 0
EDP_INT_ML_P<1> = 0
EDP_INT_ML_N<2> = 0
EDP_INT_ML_P<2> = 0
EDP_INT_ML_N<3> = 0
EDP_INT_ML_P<3> = 0

EDP_AUXCH_C_N = 0.241
EDP_AUXCH_C_P = 0.242
EDP_ML_C_N<0> = 0.244
EDP_ML_C_P<0> = 0.243
EDP_ML_C_N<1> = 0.242
EDP_ML_C_P<1> = 0.245
EDP_ML_C_N<2> = 0.243
EDP_ML_C_P<2> = 0.245
EDP_ML_C_N<3> = 0.242
EDP_ML_C_P<3> = 0.242

Any help is much appreciated! Thank you

 

[2informaticos]

Check continuity from U8510 to J8500.
EDP_PANEL_PWR_EN is high?

 

[Panrix Microelectronix]

EDP_PANEL_PWR_EN is 3v3 and steady
We have continuity from U8510 and J8500

 

[2informaticos]

"BUF_EDP_PANEL_PWR_EN 0.528"
What is the voltage there?
If 0V, then change U8510.

 

[Panrix Microelectronix]

BUF_EDP_PANEL_PWR_EN is 3.4V

 

[2informaticos]

Then PANEL_P3V3_EN_DLY should be high too; confirm that.

 

[Panrix Microelectronix]

PANEL_P3V3_EN_DLY is 3.4V

 

[2informaticos]

Then you should have 3V3/5V_S0SW_LCD.
If not, check U8500/1 voltages.

 

[Panrix Microelectronix]

I have re-tested and I do have correct voltages for 3V3/5V_S0SW_LCD

 

[2informaticos]

Then check DP_INT_HPD voltage again; it should be high.

 

[Panrix Microelectronix]

DP_INT_HPD is showing 3v3

 

[2informaticos]

You should have image at least; missing backlight only?

Did you try known good LCD assembly?

 

[Panrix Microelectronix]

Yes I tested with a known good screen and tested this screen on another board..

I still don't have any of the EDP INT values

 

[2informaticos]

I hope you've checked DP_INT_HPD level with LCD connetced...

 

[Panrix Microelectronix]

yes DP_INT_HPD was checked with screen connected. The EDP INT lines missing are the ones below which were checked in diode mode both with and without screen connected:

EDP_INT_AUX_N = 0
EDP_INT_AUX_P = 0
EDP_INT_ML_N<0> = 0
EDP_INT_ML_P<0> = 0
EDP_INT_ML_N<1> = 0
EDP_INT_ML_P<1> = 0
EDP_INT_ML_N<2> = 0
EDP_INT_ML_P<2> = 0
EDP_INT_ML_N<3> = 0
EDP_INT_ML_P<3> = 0

 

[2informaticos]

This board has series capacitors on the EDP_INT lines; no reason to check there.
If you want to make an idea, then check on the left side of C8520-9.

If T-CON board receives 3V3_S0SW_LCD, then should send back to MLB high level on DP_INT_HPD.
Then PCH starts the communication with T-CON.