Yet another 820-3115. Has a green light, but no power.

[gcain]

Customer claims the board isn't water damaged.
Gives a green light but won't spin the fan.


I get PPBus_G3H at 12.61


PP5V_S5: 4.89v
PP5V_SUS: 2.70 - 2.97v (unstable)
PP3V42_S5: 3.27
PP3V42_G3H: 3.42
S5_PWRD: 3.4v

PP5V_S3: 0v


Susing out PP5V_SUS...
---
Q7840
Pin1: 2.68 - 2.89v (unstable)
Pin3: 3.45 - 3.7 (unstable)
Pin7: 4.89.



Testing Q7822 I get;

Pin 1: Gnd.
Pin 2: 0.4v, 0.5v, 0.6v back to 0.4v.
Pin 3: 3.2v, 3.6v, 3.7v back to 3.2v
Pin 4 Gnd.
Pin 5: same as pin2.
Pin 6: same as pin 3.

 

[dukefawks]

It is trying to power on that is why you have unstable voltages. Check PP5V_S3 with a scope to see if there are any pulses there, multimeter is too slow.
Must be liquid or drop, inspect closely.

 

[gcain]

I dont have a scope yet.
Is there an alternative move I can make?

 

[dukefawks]

Nope, I have no idea how slow your multimeter is and if it is able to see the short pulses.

 

[gcain]

OK, while I try and track down a scope, maybe we can start checking from another angle.

PM_SLP_S4_L is reading at 0, where does it come from?
U1800 it seems, so why is it not sending anything?

 

[dukefawks]

It may also be pulsing......this is what these boards do if something is wrong in the power sequence.

 

[gcain]

dukefawks could the unstable PP3v3_SUS be because it is trying to start up and something is tripping or failing?

If there was no PM_SLP_S4_L it would just remain in an off state, but it appears that it is trying to progress along.

My thoughts being that it isn't U1800 not creating the S4_L it is simply cycling before it get's that far.

 

[dukefawks]

I really don't know. Check voltage to R1800/1/2/3, R1915, C2231/32/33.

 

[gcain]

R1800/1/2/3, R1915, C2231/32/33 all give me 3.304v

 

[gcain]

I'm getting;
PPVCORE_S0_CPU = 0.8v
PPVCORE_S0_AXG = 0.44v

When the schematic specifically says PPVCORE_S0_CPU should be 1.25v.

 

[dukefawks]

You cannot get PPVCORE if there is no SLP_S4. What is going on here?