820-3115 A1278 - Intermittent green light, no display.

[SamMac]

Appreciate any and all help, thanks!

So I've got a logic board where the board turns on (and green light is displayed) randomly meaning I have to plug in and out the charger before it suddenly turns on. When the fan starts spinning the green light cycles from on and off every couple of seconds and then turns solid eventually the fan then spins at like maximum rpm (the chipset SLJBC gets really warm which I why I believe that might be)
In all cases (green light or no):
PPBUS_G3H is present.
PP3V42 is present.
No display in LCD.

Thank you,
Sam

 

[dukefawks]

How warm is warm? You should be able to hold your finger on it without issues.

 

[SamMac]

It gets unusually hot, not bad enough to burn fingers though.

 

[dukefawks]

Well if it gets much hotter than a good working board it is most likely dead. Compare to another board first.

 

[SamMac]

The component F9700 has 12.57V showing at the PPBUS_G3H and giving 1.8V which slowly declines at the PPBUS_S0_LCDBKLT_FUSED end. All the connections to the LCD_BKLT gives a value of around 1.42V

Also answering your question it does get hotter than a similar board.

 

[dukefawks]

I don't see why we should be checking the backlight fuse if this board is not booting.

I suspect the PCH is dead if it getting hot like that.

 

[SamMac]

Is there anything else I can check for to confirm that the PCH being dead is more likely?

Thank you.

 

[dukefawks]

PP3V42, PPBUS, ACOK, PP3V3_S5. But if the PCH is pretty sure dead that is where you should really start....

 

[SamMac]

What would be the best way forward for this, buy the chip online or to use the chip from a similar donor board (from one that doesn't show similar symptoms)?

 

[dukefawks]

These chips don't commonly die so most donor ones will be OK, they are a bit annoying to reball though.