820-2915-A 1 beep

[powerblackout]

all_sys_pwrgd is 3.3v

When macbook turns on fan spin, no display no backlight and 1 beep every 5 seconds. Used memory out of working machine, tried both slots, the connectors look fine no water damage.

SMC bypass mode and NVRAM reset didn't change anything. Running on only ac adapter, only on battery, and on both same result.

All of the errors I find online are for 3 beeps, but I am only getting 1 beep. Is there something on the board besides the memory that can cause this to happen?

[piernov]

Re: 820-2915-A 1 beep

Check SMBUS_PCH_DATA & SMBUS_PCH_CLK, voltage & diode mode to ground.

[powerblackout]

Re: 820-2915-A 1 beep

Ah ok once I started added SMBUS to my query something could be wrong with something on there?

SMBUS_PCH_DATA 3.35V 0.45 diode
SMBUS_PCH_CLK 3.35V 0.45 diode

Red probe on ground black probe on the resistor

[powerblackout]

Re: 820-2915-A 1 beep

I'm not sure how much traffic is needed, but I don't see any traffic happening on SMBUS_PCH_DATA with my scope. I see the signal go high when I turn power on, but it doesn't do anything else.

[powerblackout]

Re: 820-2915-A 1 beep

Any ideas? I can't find any information on how to troubleshoot SMBUS issues for this board.