820-2838 greenlight, but no fanspin

acehobojoe

New member
I'm a little confused by this one. The only liquid damage is in the upper lefthand corner beside the backlight circuit. I have checked that area for shorts with no luck. I have the g3 hot rails, but no P5vS0 rail. And I think (I am new to this) the P5vS3 rail is required for P5vs0 to work. I do not have P5vs3 either. Any guidance on finding out what is going on is appreciated. thanks!


One other interesting thing: I check P5vs3 in continuity mode and everything looks good, but when plugging in DC power the impedance drops down to around 18 ohms (sill 0v)
I'm checking the line now for some mosfets that may have opened to a shorted line or something.
 
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2informaticos

Administrator
Staff member
Ooops, do NOT measure resistance to ground on a powered board, on any point!!!

Exact voltage at F7040?
Do you get steady 3.3V at L7260 and 0.9V at L7750??
Touch SMC_ONOFF_L to ground and look if L7220 pulses atleast?
If not, check if PM_SLP_S4_L and PM_PWRBTN_L pulse any.
PM_RSMRST_L should be high always, as RTC signals too.
 

acehobojoe

New member
R7760 is missing. I am not sure if that is normal. On the schematic it doesn't say nostuff. I think this is what connects the s5 to the s3 rail. I am getting s5 LDO, just no s3.
 

acehobojoe

New member
f7040 is 8.37
L7260 gives me 0v
L7750 gives me nothing

I am not sure how to check the rest for pulses and what not
 

acehobojoe

New member
no pulse at L7220 when using power on pads.
PM_SLP_S4_L gives me a steady .19v no matter what. with the pwr pads.
PM_PWRBTN_L is not pulsing either.
 

2informaticos

Administrator
Staff member
"L7750 gives me nothing"
Solve that first, if not shorted...

Also check if L6995 shows more than 30K (200k scale), as normal for MCP platform.
 

acehobojoe

New member
I'm getting no P3v3S5, which is needed for pv095. The enable pin (p3v3s5_EN) is fine, yet I am getting 0 volts out of the chip. could be a dead chip.
 

2informaticos

Administrator
Staff member
"L7260 gives me 0v"
Sorry, I forgot about this.

"what is MCP?"
Try to find a coincidence in the first schematic page.
Or look directly at schematic block.

Any short/low value at L7220/60?
Post U7840 voltages first.
 

acehobojoe

New member
So, from what I can gather, pin 4 is EN_L, which I think means enable low. This maybe means there should be voltage on this pin too to enable the circuit, but when I look upstream from there, there are two transistors that seem to come from the cpu to send a signal to it. There could be something wrong with one of the transistors or something else, but it seems likely to me at this point to be a dead mcp.
The weird part to me, is that on the schematic the EN_L pin seems to be only related to wlan, which shouldn’t be needed to achieve an S5 state.

I couldnt find find a data sheet on the chip to tell what that pin did, but I think the pin 4 is preventing it from turning on.
 

2informaticos

Administrator
Staff member
U7840 is OK.
Pay atention to the circle from pin4; that means inverted output (as _L specifies low level)!

Now post some voltages at U7201; pins 23, 29, 22, 4, 21.
 

acehobojoe

New member
It may be 0v because of R7864 missing on the PM_SLP_S4_L line. this is needed to allow the voltage through the transistor I think
 

acehobojoe

New member
from all I can tell, the signal coming from the MCP or SMC is not telling the transistor to turn on, so It must be a dead MCP
 
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