Re: Apple Mac Mini A1347 Late 2014 completely dead no power
Ok.
1) Resistance to ground is high enough so you do not have a short on the 5 volt LDO rail. However, it is not turning ON.
2) The ENABLE for this rail appears to be pin #12 of U7201. It is based on a resistor voltage divider. Once the power DCIN is docked, the resistors produce a safe lower voltage that is fed onto pin # 12 to ENABLE this always on 5 volt LDO rail.
See and post the attached voltage readings.
According to the schematic, location # 2 & pin 12 of the U7201 should be:
TURN ON: 4.8 TO 7.4V
TURN OFF: 3.0 TO 6.7V
3) If the 5 volt rail is ENABLED via pin #12 and still not turning ON @ pin # 29 of U7201 then U7201 MUST be replaced. Mobilesentrix does not carry this part which is a shame but see it available for sure on Aliexpress and other USA sites.
If you cannot source it quickly, I believe we have some of these in our building but will have to confirm. 99% that we do. Let us know if you do need this part from us. Can figure out a fair cost. I think we have a good company discount with Canpar shipping across Canada.
You will need hot air tools to replace this QFN that has a metal belly which acts like a massive heatsink. The surrounding parts should be masked with kapton tape then apply flux to this IC. Before you do any of this, take a clear picture of this area so that the QFN part can be applied back exactly as before with pin #1 in the proper orientation. Once the flux is onboard it can get crazy to locate pin #1
Ok.
1) Resistance to ground is high enough so you do not have a short on the 5 volt LDO rail. However, it is not turning ON.
2) The ENABLE for this rail appears to be pin #12 of U7201. It is based on a resistor voltage divider. Once the power DCIN is docked, the resistors produce a safe lower voltage that is fed onto pin # 12 to ENABLE this always on 5 volt LDO rail.
See and post the attached voltage readings.
According to the schematic, location # 2 & pin 12 of the U7201 should be:
TURN ON: 4.8 TO 7.4V
TURN OFF: 3.0 TO 6.7V
3) If the 5 volt rail is ENABLED via pin #12 and still not turning ON @ pin # 29 of U7201 then U7201 MUST be replaced. Mobilesentrix does not carry this part which is a shame but see it available for sure on Aliexpress and other USA sites.
If you cannot source it quickly, I believe we have some of these in our building but will have to confirm. 99% that we do. Let us know if you do need this part from us. Can figure out a fair cost. I think we have a good company discount with Canpar shipping across Canada.
You will need hot air tools to replace this QFN that has a metal belly which acts like a massive heatsink. The surrounding parts should be masked with kapton tape then apply flux to this IC. Before you do any of this, take a clear picture of this area so that the QFN part can be applied back exactly as before with pin #1 in the proper orientation. Once the flux is onboard it can get crazy to locate pin #1
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