820-3437 No PP3V3_S5

[JohnB8812]

Board came in liquid damaged primarily in the clock chip area. Had 8.58 on PPBUS, 3.42 on 3v42 and green light. Had 0 volts on PPVRTC_G3H. Replaced C1902, C1922, and C1910 because they looked bad as well as the clock chip. Now I have 3.42 volts on PPVRTC_G3H, 5 volts on PP5V_S5, but zero volts on PP3V3_S5. The only bad probe point I found was the one left of R2042 but it seems to have continuity to its corresponding spots. On the TPS, SMC_PM_G2_EN is 3.42 volts, P3V3S5_EN_R is 3.3 volts. What am I missing or where do I go from here?

 

[dukefawks]

All the basics are there so it is either a short on 3V3_S5, bad TPS51980 or a corroded trace/resistor in that area.

 

[JohnB8812]

Ok will check those and get back to you

 

[JohnB8812]

3.9 kilohms and rising despite 0 volts. Did not see really much of any corroded traces or resistors besides the ones in the clock area and everything connects. Will replace TPS tomorrow and check back

 

[JohnB8812]

Ok so replaced TPS same problem. Went back to clock chip area pulled chip noticed PCH_CLK32K _RTCX1 pad was burned so ran jumper to corroded test point now have continuity and replaced clock chip again. Same problem no 3V3_S5. I'm really stumped on this at this point nothing else looks corroded or broken. Also PM_SLP_S5_L is missing checked all test points near BIOS all connect and all of the probe points look pristine. The only other probe points on the board that look anywhere near discolored are one by the SMC for SMC isense which I don't think is related at all and then the probe points below the CPU. Is this a time waster at this point?

 

[JohnB8812]

Oh, and I still have 3v3 S5 enable.

 

[JohnB8812]

Resistance to ground on 3v3_S5 is 2.71 Kohms

 

[dukefawks]

Clock chip has nothing to do with 3V3_S5. First thing that needs fixing is 3V3_S5 now.
The basics at TPS51980? VIN, VREG3 and 5, VREF, EN, EN2?

 

[JohnB8812]

VIN: 8.58 volts
VREG3: 3.3 volts
VREG5: 5 volts
VREF: (I'm assuming pin 13) 1.0 volts
EN S4RS3: 0
EN2 3v3S5_EN_R: 1 volts

 

[JohnB8812]

R8140 and R7552 measure normal

 

[JohnB8812]

And check that EN2: is 3.4 volts measured wrong pin
So I'm missing EN1 P5vS4RS3

 

[dukefawks]

Of course P5vS4RS3 is missing you just told me 3V3_S5 is not present.... Double check is there 3V on L7560?

 

[JohnB8812]

Zero volts on both sides of L7560

 

[dukefawks]

VREF2 at 1V is not good, should be 2V there. Check voltage on R7552 and go over the TPS51980 area again.

 

[JohnB8812]

I have 3.42 volts on both sides of R7552 and there is continuity throughout to the chip. Could TPS I used be bad? Pulled from donor

 

[JohnB8812]

And TPS area looks normal like literally no sign of broken traces anywhere everything seems to connect with continuity.

 

[JohnB8812]

Q7560 has solder balls sticking out of it... maybe the issue?

 

[JohnB8812]

Pulled Q7560 measured for short on both sides of L7560 and get 2.47 Kohms resistance to ground. Does this mean replaced TPS and the FET and I'm good or is this trash?

 

[dukefawks]

I have no idea. TPS is getting enable signals so it should work. As I said VREF2 should be 2V and you have 1. Bad TPS, bad cap, resistor, trace it is somewhere around the TPS.