Missing SYSCLK_CLK25M_SB

[MDY]

This board firstly run ok with video but fan at full speed.

It has liquide damage arround ISL and ppbus 12.26V. Aftert clean this area, I already have 12.56V but now doesnot power.
3V_S5 are present
5V_S3 appears only when plug the charger the first time for 0.1 seg. It doesnot pulsing.

If I remove R1872 to separe PCH from clock it start pulsing each 8 seg all rails except CPU rail.
I replaced clock chip 3 times and all the same:

32khz are present
SYSCLK_CLK25M_SB - NOT present
I took working clock chip from another working board and same. Dont have 25Mhz.

I do have =PP3V3_S5_SYSCLK and =PPVBAT_G3_SYSCLK
But something is wrong and clock doesnot generate 25Mhz. At this point I dont know what more to check.

 

[dukefawks]

Must be corrosion somewhere else too. As you have again not mentioned what board this even is I have nothing to advise.

 

[MDY]

It is 3115

 

[dukefawks]

Look at clock chip circuit and tell me when the 25MHz will be enabled....

Checked R7402/03? Crap under SMC? Checked all rails for shorts?

 

[MDY]

I can see that clock chip is power by PP1V8_S0 but I am not sure if this rail is need to generate 25mhz, as PCH need 25mhz to run and S0 depend from PCH too. Also xtal is inside PCH...
Or 25khz are enought to run PCH and 25mhz are need later for CPU work and depend from PP1V8_S0 and xtal from PCH?

 

[dukefawks]

What board did you take the clock chip from, there are a few different versions and not backwards compatible!

 

[MDY]

From 2936. As I see 3115 and 2936 are the same.

 

[dukefawks]

I still stand by my other suspicion, R7402/03 or crap under the SMC. That is if ALL_SYS is also pulsing high, so check that first.

 

[MDY]

These resistors are ok and SMC already reflowed few times. ALL_SYS pulsing ONLY if I remove R1872. This mean something?

 

[dukefawks]

Vcore coming on?

 

[MDY]

If I remove R1872 to separe PCH from clock it start pulsing each 8 seg all rails except CPU rail both coils.

 

[dukefawks]

I really have no other ideas. Must be corrosion somewhere, you saw it before cleaning, I have no way to tell where it was.