820-3437-B no light and fan spinning fast

[brumbrum]

Good morning everyone,
I Have a MacBook air logic board that first came in for no power.
I removed ssd and wireless card.
With charger I got only orange light, and if I press power button the light became green just for 2 seconds (the system feels when I press power button).
The issue it's: no boot, no power on, I have v core, 1.7v, but as I plug the charger, green light 2 seconds and orange light with fan stuck spinning.
Nothing except cpu on board is hot, no corrosion, I haven't found any short, and I checked that voltage rails checked and are ok:

 PM_SLP_S5_L – 3.3v
 PPBUS_G3H
 PPBUS_S5_HS_COMPUTING_ISNS
 PPBUS_S5_HS_OTHER_ISNS PP5V_S5
 PP5V_S4RS3
 PP5V_S0
 PP3V3_S5
 PP3V3_S4
 PP3V3_S3
 PP3V3_S0
 PP1V8_S3
 PP3V42_G3H
 PPVRTC_G3H
 PP5V_S5
 PP5V_S4RS3
 SMC_ADAPTER_EN
 PCH_SRTCRST_L

Issues:

 PM_SLP_S4_L -> 0v
 PM_SLP_S3_L -> 0v


Can someone help me to fix that crazy board? thank you

[piernov]

Re: 820-3437-B no light and fan spinning fast

Keyboard is probably bad.
If you have S3 and S0 rails present, PM_SLP_S4_L and PM_SLP_S3_L cannot be 0V.

[brumbrum]

Re: 820-3437-B no light and fan spinning fast

But I've disassembled the board, with only magasafe connected, and problem is still the same

[piernov]

Re: 820-3437-B no light and fan spinning fast

With a good keyboard it shouldn't cause Magsafe light to turn green then orange again when pressing power button (could also be caused by touchpad but less likely).
It's not clear what the problem is though. Your measurements don't really make sense and you haven't properly described the symptoms. You say no power but at the same time "fan stuck spinning" and CPU getting hot.
So, with only the board: orange light on Magsafe? Fan spinning?
With a USB drive plugged in, activity LED blinking?
Chiming with speakers connected?
Image and backlight with LCD connected?

[brumbrum]

Re: 820-3437-B no light and fan spinning fast

ok I'm sorry. I'm trying now to explain better now after Smc replacing.
No power with battery connected, no sign of life. No chiming or any sound, no image and no backlight.
If I plug magsafe, I get green led and fan spinning for 2 seconds, after that fan stop and led became orange. With orange led, fan keep spinning stuck at the same speed, and only cpu is hot, and of course no chiming or any sound, no image and no backlight.
With a USB drive plugged in, activity LED not blinking.
The behaviour of the board is the same, with or without keyboard and touchpad connected.

[piernov]

Re: 820-3437-B no light and fan spinning fast

So with logic board, DC-in board and fan: fan spins, stops and spins again?
This board should have fan spin, stop, spin, stop and then spin again instead.
So you replaced the SMC? What led you to replacing the SMC? Did you take the SMC from same model donor board?

[brumbrum]

Re: 820-3437-B no light and fan spinning fast

I already replaced the smc cause under microscope I noticed that there was a little "ball" (like blow up) on the chip, even if under the chip everything was ok.
I didn't have a similar donar board to take it from, so I bought a new one with similar number:

the new one:
LM4FS1BH 5BBCIG 48A491W

the old one:
LM4FS1BH 5BBCIG 33A6GSW

But the issue is the same.

[piernov]

Re: 820-3437-B no light and fan spinning fast

SMC must come from same model donor board. It has a firmware that's specific to the board model.

[brumbrum]

Re: 820-3437-B no light and fan spinning fast

oh, thank for this info. so, it was my mistake, I didn't know it. Now should I buy another one already programmed for this model? or can I program it in any way?