820 3209 no image

[EJS]

820 3209, no image/no chime fan spins. PPBUS 8.39v, VCORE is present, missing LCD_IG_PWR_EN.

 

[JohnB8812]

Any RAM beep?

 

[EJS]

No, no sound at all, dont even get a chime

 

[JohnB8812]

Inspect for corrosion near R7402/3?

 

[2informaticos]

Do you get USB activity?
Disconnect LIO flex and try USB connector from MLB.

 

[EJS]

JohnB I inspected R7402/3 area like you mentioned, and while I did not see any corrosion, it does look like someone has reworked this area in the past, most likey U7400 has been replaced.

 

[JohnB8812]

Inspect R7402/3 for being blown and inspect traces to and from them to U7400

 

[EJS]

R7402 has proper resistance, and has .337v on CPUIMVP_TON

R7403 has proper resistance, and has 1.796v on CPUIMVP_UGATE1_R

 

[2informaticos]

You have VCORE, so most likely no problem at all on U7400 area.
Will still be good to post L7550 voltage.

"Do you get USB activity?
Disconnect LIO flex and try USB connector from MLB."
???

 

[EJS]

2inform, I sm not getting USB activity, also, something I over looked PPVCORE_S0_CPU is present, PPVCORE_S0_AXG is missing.

 

[2informaticos]

If no USB activity, board is stuck; no reason to look for video...

Check PLT_RESET_L and PLT_RST_BUF_L.
If any missing, post PM_PCH_SYS_PWROK.

Check for 25MHz at SYSCLK_CLK25M_SB.

 

[EJS]

PLT_RESET_L 1.048v

PLT_RST_BUF_L 3.345v

PM_PCH_SYS_PWROK. 3.40v

SYSCLK_CLK25M_SB .796v

 

[JohnB8812]

PLT_RESET_L being low could be your problem it's supposed to be 3.3

 

[2informaticos]

I think PLT_RESET_L has a weak pull-up inside PCH.
Maybe some chip connected there is throwing signal down, or crap under PCH.
Maybe you can force it with external 33-47K to 3V3_S0, worth to tray.
First see if reflow PCH to 180 degrees help; use quality flux, not "chinese honey".