A2779 - 820-02841 - No image - U6070 troubleshooting

[2informaticos]

Seems that you don't understand what you are looking for.
Mentioned signal must be close to 0V; is related with the current consumption from 3V8_AON.

Did you check if JP600 gets correct power rails?

 

[joesklar]

Yes I don't know everything, that's why I pay the forum membership .

JP600 has no power going to it. Power in via pins 37 & 38 "PP3V8_AWAKESW_TCON" from what I can tell this power is coming from UP710.

All readings taken with LCD connected.

PPDCIN_AON - 19.8V
PPBUS_AON - 12.3V
PP3V8_AON - 3.8V
PP5V_S2_MAIN - 5.1V
PP3V3_AON - 3.3V
PP5V_AON_P3V8AON - 5.0V
PP1V8_S2SW_SNS - 1.8V
PP1V2_AWAKESW_BLC - 1.2V
PPBCON_AWAKESW_BKLTCONN_VIN - 3.3V
PPMDB_AWAKESW_TCON - 0V
PP3V8_AWAKESW_TCON - 0V

UP710
PIN 1 PP1V8_AON - 1.8V
PIN 2 LCD_PWR_EN - 0V
PIN 3 PMU_SYS_ALIVE - 1.79V
PIN 4 EDP_PANEL_PWR_EN - 0V
PIN 11 EDP_PANEL_1V8_EN - 0V
PIN 13 EDP_BKLT_1V29_EN - 0V

LCD_PWR_EN coming from U8100. I don't like where this is going...

 

[2informaticos]

UP701 should deliver power to JP600, before image appears.
Post UP701/10 voltages; LCD connected.

 

[joesklar]

I think the readings I gave above the LCD connector must have been misalgined. I tested again and got the following:

UP710
PIN 1 PP1V8_AON - 1.79V
PIN 2 LCD_PWR_EN - 1.79V
PIN 3 PMU_SYS_ALIVE - 1.79V
PIN 4 EDP_PANEL_PWR_EN - 1.79V
PIN 11 EDP_PANEL_1V8_EN - 1.79V
PIN 13 EDP_BKLT_1V29_EN - 1.79V
PIN 10 EDP_PANEL_DISCHARGE - 0V

UP701
PIN 1 PP3V8_AON - 3.8V
PIN 2 LCD_PWR_EN - 1.8V
PIN 3 PP3V8_AON - 3.8V
PIN 5 (SCHEMATIC) - 0V

On closer inspection, there is a solder blob sticking from the underside of UP710. I will reflow and post readings again. I assume that EDP_PANEL_DISCHARGE must be live for QP700 to output and in turn power PPMDB_AWAKESW_TCON.

 

[2informaticos]

Don't touch UP710 yet.
You may have bad UP701; it should deliver output voltage.
Check first diode mode at its output; w/ and w/o LCD connected.

 

[joesklar]

UP701 tested at RP700 and CP718

LCD connected: 0.425
LCD disconnected: 0.849

 

[2informaticos]

Then replace UP701; if still no output voltage.

 

[joesklar]

Hi,

I replaced UP701 as advised, but still no voltage. All readings remain as prior to swap.

Pretty sure QP700 is an en N-channel, so it wants voltage on the gate to turn on. Because pin 10 (EDP_PANEL_DISCHARGE) of UP710 is 0V, it is not switching...

What are your thoughts?

Thanks

 

[2informaticos]

Why would you want to enable QP700?
Do you know what DISCHARGE means???

Check if UP701 delivers output voltage with screen disconnected; at least in the first seconds, when machine chimes.

 

[joesklar]

Hola Vali,

I have been away and so haven't been spending too much time on this. Just back at it now.

Sorry no I don't understand that circuit, can you explain what the discharge function does there??

Regardless, I replaced the UP701 and there is since an image, but still with no backlight. Since then, another issue has arisen.

I was probing around the board and when I attempted to turn back on, there is now only 5V - 0.05-0.010A being drawn. Obviously something has happened and I'm trying to understand what.

I don't quite understand this U5200. Can you explain the power sequence at high level along with the U5500/UF400/UF500 (CD3217)?

I guess the U5200 is working as PPBUS_AON has an output.

PPDCIN_AON: 5.2V
PP5V_CHGR_SW: 4.5V
PPBUS_AON: 12.3V
PP3V8_AON - 0.06V

I hope you have a lovely xmas!

 

[2informaticos]

The discharge circuits must discharge any remanent voltage; once corresponding power rails have been already disabled!

Remove F5200/1 and check C5250 voltage.

 

[joesklar]

Thanks for the explaination.

I removed both fuses and the reading is the same. 12.3V on C5250.

Thanks

 

[2informaticos]

resolder the fuses.
Check diode mode to ground at 3V8_AON power rail.

Post U5700 basic volatges: pins 8, 7, 5, 12.

 

[joesklar]

PP3V8_AON diode mode - 0.369

U5700
8 - PPVIN_P3V8AON - 12.3
7 - PP5V_AON_P3V8AON - 5V
5 - P3V8AON_PVVC - 0.87V
12 - P3V8AON_PWR_EN_R - 4.5V

Is the enable signal too high? I can't find a datasheet for RAA225501C.

 

[2informaticos]

Possibly bad U5700.
Check diode mode to ground there.
If low, remove C5701 and check again.

 

[joesklar]

What do you consider low? I don't have access to any reference values.
Thanks

 

[2informaticos]

PVCC is internally generated by U5700.
I don't consider low; no ideea what's the reading there...