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Hello, I have that board on which we've replaced the whole topcase (kb + tp) but same behavior. It will sometimes works fine after sleep but sometimes you just get no TP+KB. External USB mouse and keyboard will work fine however. I can see the caps lock light on when this is happening. Any...

No, still a flat 0V

Hello, That board is missing the CPU power rail but it is in an S0 state. The CPUIMVP_VR_ON signal is on at 3.3V Corrosion was worth between R2415 and C2411, on the probe point, rail PP1V05_S0_PCH_VCCDMI_FDI This rail is at 0V. That rail comes from PP1V05_S0 which is present at 1.05V Probe...

Well back to step 1... I've replaced U7400 and still got the CPU rail not trun on. Then I decided to replace Q7510 and Q7520 and I am back to a quarter fan spin. If I understand well, I should replace U7400, Q7510, Q7520, Q7550 and Q7560 , all at the same time, if the problem comes from the buck...

Not sure to be honest... I input 5V onto that rail to find out what would become hot. I couldn't find anything. Then plugged back the fan to start doing some other measurements and saw the fan spinning normally. That's then I realize I would not get any voltage on the CPU.

Hello, Well... after spending some more time on that board, I finally got the short to be gone however I am not getting CPU_VCORE. The enable signal on CPUIMVP_VR_ON is 3.3V and PP5V_S0 is 5V. I have measured voltage on Phase 1 and 2 and I am getting 0V. Resistance to ground on these rails is...

I did remove that chip and still get the artefacts on the LCD screen. That board looks very clean and I can't find any corrosion anywhere. I don't get your message Duke, do you mean I am missing something? (since my brain won't turn on here...)

Hi, I've been working on that board for a while but I still can't get it... Wherever or not it is plugged to the charger it may stop anytime. I can use it for a day without any issue but the next one it may shutdowns 3-4 times for no particular reasons. Everything other than the mainboard...

No it's not coming on. Actually you lead to find that this rail is shorted...

Sorry, I meant reballing another chip from a donor board, like I would do with an SMC. Can that chip interacts with the internal display though? (I am getting the artefacts on both LCD and screen connected to display port)

Because I did spend already 5 clock chips on that board so I believe there is 99% of chance that I couldn't screw up that much. However you are right, removing it won't make any harm.

That board can stay running forever, fan spinning however when I try to measure the voltages near U1950 the board just dies. Could I be on a hint or is it a normal behavior? (thinking it could create a slight voltage fluctuation which would cause the CPU to stop...)

Hi, We have that very clean board without signs of liquid damage which shows artifacts on the screen, right at the EFI boot menu. So we were suspecting a dying GPU however we realized that U2800 was boiling hot. This chip seems to be related to the thunderbolt ports. Could it be also related...

well I did remove everything on that line except the clock chip and still 5k ohms resistance to ground... CPU is toasted

Ok, I realize now that I need to understand the difference between both measurements... my apologies Resistance to ground is 6k ohms, not Mohms like my other board. Since I assume bad caps would create a short and that I've measured that the resistance are fine... is my CPU toasted? or should...

I agree with you however here is what I've done today: - Resoldered a new clock chip from pool of new chips (I also used some from donor boards previously) - Redone my solder around the chip a few times - Check for steady PP3V42 and PP3V3 voltages with my oscilloscope and they are both - Check...

I am getting 0.4v drop to ground on PPVRTC_G3H. Also I've checked that resistance to ground with another board and it is similar. Finally,I've checked all the resistor going to the PCH and the values are good.

Hello, I have that board which used to have a nice 0V on SMC_PM_G2_EN. Since I've replaced the SMC it seems to be a steady 3.3V however I have now a 1.2V on PPVRTC_G3H that I don't recall having prior to the SMC replacement. I've replaced twice the clock chip and have checked all the incoming...

Hi Duke, I did check these and they measure all fine. I've also reflowed the SMC in case of a bad connection underneath it but no cigar. I also tried a different BIOS chip. Any other idea please?

Hi, I have that board which has the quarter fan spin. It has the normal sign of corrosion on the top edge of the board but looks quite good though. I have measured the voltage drop to ground on the S3 and S0 rails and have found a 0.115v drop ground on PP5V_S3 compared to a 0.425v drop to...