820-3115 one beep, all power rails present, no liquid spilled

[roy.ruan]

having a 820-3115 board. all power rails present but can't post video, always one beep and goes a loop.

PP0V75_S0_MEM_VTT_A=0.75v
pp1v5s3 ddr =1.5v

cpu vcore 1.1 around

having no clue than a dead cpu or PCH, any thoughts please?
thanks

 

[roy.ruan]

by the way, tried both RAM slots already

 

[Repairable]

Check lcd conmector
pin 4-6-7
does iT detect lcd

pram reset?
does iT chime?
light on USB mouse?

 

[dukefawks]

a) What has the LCD connector to do with 1 beep?
b) How can you do a PRAM reset if the board beeps, it is not able to boot.
c) It beeps so it does not chime
d) It beeps so it does not boot so how can it have a light on the mouse?

Now the real solution. The board is probably not seeing the RAM. RAM is detected through SMBUS, the one with R5200/01 as pull ups. As you can see there are many things on this bus including the backlight driver. First check diode mode on both data lines.

 

[roy.ruan]

thanks Duke
that's great path to go. checked the schematics ,page "PCH SMBus "0" Connections"
so many stuffs connecting to it, let me check diode mode first tomorrow and inject power if it's shorted.

 

[roy.ruan]

diode mode
r5200 pin1 0.313 pin2 0.420
r5201 pin1 0.314 pin2 0.422

both have 3.3v when the board is powered on

seems right to me and nothing short and pull 3.3 down?

 

[dukefawks]

One beep does not always have to be a RAM issue though. This one will suck, most likely it is something on the RAM SMBUS or a PCH issue. BIOS is also an option

 

[roy.ruan]

huh, yea BIOS. but it looks untouched so probably not the one. i will flash it tomorrow though and see how it goes.
then will be the PCH, if replacement of PCH doesn't solve. maybe it's time to say goodbye to this POS

 

[dukefawks]

Before you touch the PCH you first remove all chips connected to the RAM SMBUS like backlight driver, mikey, etc.