820-00165 No Video

[iClub]

This mac has suffered oxidation on the SMC and U5110.
Chime, activity on USB, but no image, only on external video.
I used a good display.

EDP_PANEL_PWR 0V.

 

[Master Liu]

What is the working current of the motherboard？

 

[2informaticos]

Do you get 3V at pins 18/19 of J8300 in the first few seconds, when chime?
If yes, pin 14 should go high at same time.

 

[iClub]

PP3V3_S0SW_LCD_UF 0v, no pulse.
L8304 okay.

 

[2informaticos]

Check for pulse there without internal LCD connected.
If not present, check if EDP_PANEL_PWR pulses at the mentioned time.

 

[iClub]

'' If not present, check if EDP_PANEL_PWR pulses at the mentioned time. ''
0V, no pulse when mac has the chime.
DP_INT_HPD_CONN 0v, no pulse.

 

[2informaticos]

Did you try without LCD connected?
Check directly when turns on, before the chime.

 

[iClub]

No display connected EDP_PANEL_PWR 652mV pulse.
mode diode 0,631V

 

[iClub]

I tested another BIOS file with a clean ME region, but no result.

 

[2informaticos]

Looks like PCH problem.
Inspect for other corroded components.
Possibly accumulated crap underneath PCH/CPU; heat it as usual.