[SOLVED]820-00165 No Boot. Has 1.8V on vcore.

[bjf]

This board spins up for about 5 seconds, fan dies, then spins back up. Has 1.8V on vcore after originally having 1.7V until I fixed U1950 area. No chime. PRAM does nothing. No video/backlight. I attached pre-ultrasonic pics. Not sure where to go next.

 

[dukefawks]

Most likely corroded trace/resistor from U6100 to the SMC. Check all traces and termination resistors from U6100.

 

[aprendiz]

Did you remove J6100??? do a continuity test on SPI lines and resistors...

 

[bjf]

Yes, pulled J6100. I have continuity on all 22 of the SPI lines. Resistors are good. I see this exact issue on a lot of boards. Fan up, down, up, full vcore, but no boot.

 

[dukefawks]

U1900 should be replaced and U1950 replaced and if already done inspected again. Close up picture of affected area may also help.

 

[bjf]

No Title

Replaced U1900. No change. All of these boards always need U1950 replaced so that was replaced too.

 

[dukefawks]

C1950 should not sit that way, is there 3V there? Trace to R1961 looks sad, I know it is no stuff but trace needs to be intact, so check for continuity around U1950.

 

[bjf]

No change. I fixed that R1961 trace. I originally thought it wouldn't matter so I was going to just leave it. C1950 needs to go sideways on these to reach the scraped off trace when the original pad is often blown off. 3.4V is solid in that area.

 

[bjf]

No Title

Ok, got it. It did end up being the U1950 circuit. The PM_PCH_SYS_PWROK trace was blown at the pad I circled. It was't getting to R1962. Thanks for the help.