Need help for a 820-3115 board, no video output

[roy.ruan]

Hi
Im having a 820-3115 board. all voltages present, but no video or image on screen. not the no back light ,but no image.
when plug in usb mouse, the light is up.

no beeps, no chime, can't find liquid spilled. where should i start?

thanks

 

[aprendiz]

CPU Vcore present???

 

[roy.ruan]

yes it does. 0.89v

 

[aprendiz]

Does it beeps without memory??

 

[dukefawks]

0.89V and light on USB mouse does indicate the board is working to some extent. 4 pin speaker connected, that is the one that will chime.

History of the board? SMC fucked with? LCD connector corrosion?

 

[roy.ruan]

connected the speaker already,definitely no chime.
it looks perfectly fine and no one ever touched. saw a point or two with green stuffs around the board, but really can be moisture i think

 

[dukefawks]

Again, is there beep with no RAM. 4 pin case speaker must be connected.

 

[roy.ruan]

YES when no ram is inserted, one beep

 

[dukefawks]

Do a PRAM reset with an external USB keyboard and see if chime returns.

 

[roy.ruan]

tried that at the first place already, not response to PRAM reset

 

[dukefawks]

Could be anything, any history?

 

[roy.ruan]

that's the tough part, looks perfect fine physically, and machine seems never got worked on before.
we do see a dot or two of greenish stuffs on the side, but most likely just caused by the moisture
having tough time with this one, not sure if should risk replacing the PCH

 

[dukefawks]

BIOS would be a better suspect than PCH. Also is the white sleep light going off after USB mouse lights up?

 

[roy.ruan]

you are right! I flashed the bios and it booted up all the way and worked.

thought about it the first place and thought APPLE's bios doesn't crash much as other brands. rarely seen .(maybe 2 or 3 so far for these years)

I do wonder what made the bios crash?? (since i don't think there is bios update option for the macs)

thanks Duke!

 

[dukefawks]

Did you transfer over the old ME region?

 

[roy.ruan]

I had a cleaned ME one, just changed the SN and flashed, tested all fine.
still wonder how a good machine would have the bios crashed all a sudden though, searched online a lot but didn't seem to find the answer? do you have any clues?
thanks