Apple Mac Mini A1347 Late 2014 completely dead no power

[Ivanocabolocov]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

hello.I have excactly the same problem as you had with the mac mini...i wonder did you ever get the full schematic cos at the moment im stuck....thanks

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Hi. What is the logic board number for your box?

It should be of the format 820-xxxx.

[alexanderk23]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Hello everyone,

Recently bought a dead 2014 Mac Mini (same model and board, same symptoms, no signs of life).
PP12V_G3H is fine, as are the LDO voltages @ TPS51980 (U7201), but PP5V_S4_REG / PP3V3_G3H are missing.

By measuring the resistance at L7220, I found that PP5V_S4_REG is fully shorted to ground.
The reason was the tantalum cap on one of the two USB power switchers, so I removed it and now the short seems to be gone.
However, I cannot check the result, since I managed to lose the previously removed Q7220 somewhere

Although there is no apparent short circuit at L7260 / PP3V3_G3H, with a cold plug into the outlet (the caps are discharged) the voltage at L7260 briefly rises to ~3.4v and immediately drops to 0v.

Corresponding U7201 voltages are:

12 P5VP3V3G3H_REG_EN = 1.8v
15 P3V3G3H_COMP2 = 2v
16 P3V3G3H_VFB2 = 0v
17 P3V3G3H_CSN2 = 0v
18 P3V3G3H_CSP2 = 0v
20 PM_P3V3_G3H_PG = 0v
21 P3V3G3H_EN_SS = 2v
22 P5VP3V3_VREG3V3 = 3.3v
23 PP12V_G3H = 11.9v
24 P3V3G3H_DRVH = 0v
25 P3V3G3H_LL = 0v
26 P3V3G3H_VBST = 4.7v
27 P3V3G3H_DRVL = 0v
29 PP5V_G3H = 5v

Since I have neither repair experience nor schematics, I can only assume that either U7201 or its surroundings is faulty, or it stops generating pulses due to a short somewhere downstream.
So I would really appreciate any advice on this.

Thanks in advance!

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

@alexanderk23, what is the logic # of your board ?

It should be of the format 820-xxxx.

[alexanderk23]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

@mon2, it's the same 820-5509-A board.

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

The enables to U7201 are present.

The LDO rails (3v3 & 5v0) are present.

The mosfet HIGH and LOW drivers are not working since they are @ 0v.

I would consider to replace U7201. It is a common part on Aliexpress.

Also recommend to source spare Q7260 CSD58872Q5D mosfets at the same time - just in case.

Do check the resistance to ground on L7260, pin # 2.

[alexanderk23]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

@mon2, thanks a lot!

I would consider to replace U7201. It is a common part on Aliexpress.
Also recommend to source spare Q7260 CSD58872Q5D mosfets at the same time - just in case.

Ok, already ordered from a local supplier, now waiting for delivery.

Do check the resistance to ground on L7260, pin # 2.

Can't get a stable reading, maybe it's outside the range of my cheap meter.

[waakye]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Alexanderk23, follow mon2 directions as he is very knowledgeable. With his exceptional expertise I successfully repaired my Mac mini and it was the U7201 chip.

[alexanderk23]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Thank you very much @mon and @waakye for sharing your experience!

A couple of hours ago I received my order and immediately soldered the Q7260 mosfet back in place. After that, all the required voltages are in order, including PP3V3_G3H. The Mac is now working fine. Yay!

It turns out that when the U7201 does not register the correct output voltage on its 5v channel (it was not there because there was no mosfet), it turns off its 3v3 channel as well.

This was not obvious to me, since there is no datasheet on the U7201. But such protection against undervoltage is described in the datasheets for other similar chips from the same manufacturer. So the whole thing turned out to be just a broken capacitor

Thanks again!

[waakye]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Glad to know you fixed it.

[hawkinf]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Hi! i have a problem with 820-5509-A, it only have 3V on U7201, but i dont have the 5V. So... seems that the LDO Voltage i only have the 3V and not the 5V, have any ideas? U7201 defect?

[hawkinf]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

I got a TPS51980 spare (U7201), but the problem persists, I think the problem maybe in the control signal in the pin4 of U7201 (P5VS4), i got the 5V, and then goes to 0V, in an infinite loop.

[hawkinf]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

The 5V from S4 is ok now. But now i dont have the VCORE voltage. Now suspecting U7400 and/or Q7500+Q7511, Q7520+Q7521, U7510 / U7520

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Remove all power. Meter in lowest resistance scale.

Check the resistance to ground of the VCORE rail. We are checking to see if the CPU could be possibly shorted.

What is the resistance and scale used on your meter for this measurement ?

[booyabeetz]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

I also have a Mac mini A1347 that is stone dead, no power. I am in process of digesting what was discussed in this thread so I can follow along. I am new to mac repair so it would be easier for me to get my bearings if I had the schematics for this model.

Logi.wiki suggests that the schematics for 820-5509-A are available however I could not find them. Could someone please point me in the right direction? Thanks in advance.

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

@booyabeetz, what is the history of this machine? Worked one day, dead the next?

What is the status of the diagnostic LEDs? Do you see even a single LED ON when powered?

Do you have test equipment like a multimeter? Hot air tools to repair the unit?

[booyabeetz]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

@booyabeetz, what is the history of this machine? Worked one day, dead the next?

What is the status of the diagnostic LEDs? Do you see even a single LED ON when powered?

Do you have test equipment like a multimeter? Hot air tools to repair the unit?

Hi Mon2. Thank you for the reply. The owner of this mac mini says that one day it suddenly made a violent "pop" sound and the smell of smoke was immediately present in the room. Ever since that happened the mini has been completely dead.

With some further investigation I ended up taking off the heat sink assembly from the board and found that the CPU/GPU package is noticeably damaged. Specifically the smaller die looks like a broken mirror. At this point I would assume that the violent pop came from the smaller die. I would classify this as a no-fix given that this package is BGA and not worth the time and money to mess with. I don't have a BGA rework station anyway.

I will say that the cooling design for this unit is very curious. The larger die on the CPU/GPU package has direct contact with the heat sink through a pronounced copper pad while the smaller die appears to have no contact with the heat sink at all. I am not familiar with the designed operating temperatures of the smaller die however I wonder if skimping in this area had something to do with the failure...

[mon2]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Yes, a no fix if CPU. We have a very advanced bga automatic work station (Seamark) but not yet confident to deal with the larger devices. Working well for small parts we have replaced.

Consider a bottom side heater along with a bga low cost rework station for future jobs.

[booyabeetz]

Re: Apple Mac Mini A1347 Late 2014 completely dead no power

Yes, a no fix if CPU. We have a very advanced bga automatic work station (Seamark) but not yet confident to deal with the larger devices. Working well for small parts we have replaced.

Consider a bottom side heater along with a bga low cost rework station for future jobs.

Thank you for the advice. I will keep that in mind.

I forgot to add some additional information for posterity. Based on the markings it appears that the CPU is an SR1ZV Intel Core i5-4278U. It would be interesting to see if anyone else has seen this particular failure as well...