Apple Mac Mini A1347 Late 2014 completely dead no power

[mon2]

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

[waakye]

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

So I measured the R7204 and it's reading 6.8k ohm instead of 100k ohm. I also measured the R7203 and it reads 88.8k ohm instead of 511K ohm. Will the massive drop i voltage cause the issue am having with the mini not turning on?

[mon2]

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

Can you post the voltages at the same 3 locations? Then we will know for sure.

[waakye]

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

Hi, I have the voltages attached

[mon2]

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

Can you (carefully) hot air remove R7203 and just leave on one pad?

Then measure the resistance.

Solder R7203 back again so it is not lost.

Repeat to measure the resistance for R7204 with the same method.

The reported resistance values and output voltage are not making sense.

Yes, if the voltage @ enable pin # 12 is too low, the LDO rail will not turn on.

At this time, not 100% clear on what should be the ideal trigger value here.

Very strange that the resistance being read do not match the values in the schematic but these could be revised resistor values on your actual logic board.

Perhaps someone else can review this regulator and post their comments. If I recall correctly, A1466 macbook laptops also use this regulator - will check what they are doing there and post back.

[waakye]

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

Both resistors measured the right values however I lost the 511k ohm resistor. I will give some from digikey.
I am really puzzled now. I thought it will be straight n simple I guess wrong. Am willing to try something else. I guess I need to replace the U7021.
Thanks mon2

[mon2]

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

Check if Arrow has the resistors. They are dirt cheap. We have free shipping with Arrow with our company account - regardless of dollar amount.

Send me a PM and can have them drop shipped to you.

On the resistor values, do you recall the exact values of each when the parts were out of circuit ?

Based on comparison, other Apple designs are enabling this pin 12 (ie. inside the A1466 logic board) via a GPIO pin. Most likely the voltage will then be +3v3 as a logic high. You had reported around 4 volts.

Do not have direct experience with this switching regulator so perhaps someone else can share. Most are reporting that if the rails are not on, replace this IC.

Concerns are:

a) what is the max voltage for the pin #12 before it is considered too high?

b) why are the resistor values you have measured not the same values as in the schematic ?

c) what is the nominal voltage for the pin #12 to enable the LDO?

Digikey will charge $8 for shipping these low cost parts. Arrow usually takes 2 business - sometimes lucky to receive in 1 day.

[waakye]

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

Hi mon2, I will check with Arrow. When the resistor were out of the circuit for the 511k ohm I was reading .512M ohm and for the 100k ohm it was reading .100M ohm. Do you guys have the U7021 chip? Please ok pricing.
Thanks again

[mon2]

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

Hi.

1) Yes, we do have U7201 in the building. Just need to locate it. Will check once at the office in the morning.

2) On the resistors,

511k 0201 1% precision

https://www.arrow.com/en/products/nr...nic-components

100k 0201 1% precision

https://www.arrow.com/en/products/rc...ctro-mechanics

3) Glad to hear that your resistor values match the original schematics

4) Strange that you had ~4V on pin 12. This may allow us to conclude that U7201 is damaged.

Based on the online resistor voltage divider calculators, you should have about 1.96V => 2v0.

https://www.allaboutcircuits.com/too...er-calculator/

If we assume this device's core is powered from 3v3, then ~2v0 is considered a logic HIGH which means the VREG5 (pin 29) rail should turn ON. Personally do not have access to the datasheet for U7201 but @ ~4V0 on pin 12 can be dangerous for a chip with 3v3 powered GPIO pins.

Suggestion is:

a) source the fresh resistors - PM me and we can drop ship them to you from Arrow.

b) have U7201 at our place - once we locate them, can ship them to you by courier or Canada Post.

c) after replacing the resistors, check the voltage at the junction of pin 12. It must be around ~2V0. If not, not to worry as the defective U7201 may be causing this quirk. Remove it from the PCB but please be sure to use flux and enough heat to remove the IC without damaging the SMD pads. Gently nudge the IC with tweezers till the solder melts on its own and then remove off the logic board. You may want to work with a local tech or cell phone repair shop for this minor surgery. With the IC off you must see ~2v0 for pin 12 pad. This is based on the +v = 12v feed into this resistor voltage divider.

Do you have kapton tape to mask over the SMD parts you do not wish to disturb? Some use aluminum foil or even coins for this.

d) then solder in the fresh U7201 device.

[waakye]

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

Hey Mon2,
I wrestle with the U7201 device and I was able to remove it and solder on the new chip and below are my findings:
on U7201 (TPS51980) pins
PIN 12 EN = 1.92 VDC
PIN 4 EN1 = 0 VDC
PIN 5 PGOOD1 = 0VDC
PIN 1 DRVH1 = 0VDC
PIN 20 PGOOD2 = 0 VDC
PIN 3 RF = 0VDC
PIN 23 VIN = 11.88VDC
PIN 2 V5SW = 0VDC
PIN 29 VREG5 = 5.00VDC
Pin 31 = 4.99VDC
Pin 22 = 3.29vdc
Pin 13 = 1.98vdc
Pin 14 = 4.99VDC
Pin 15 = 1.98vdc

Thanks in advance

[mon2]

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

hi. good to hear.

1) voltage readings @ 1 and 2 of the attached locations ? According to the calculator, this looks to be correct if the input voltage is around 12V.

2) voltage on pin 21 (EN) / C7215 of U7201 ? (P3V3G3H_EN_SS)

3) voltage of P5VS4_EN1 (Q7210) = pin 4 of U7201 ?

4) voltage on L7220, pin 1 ? (PP5V_S4_REG) ? This mates with pin 2 of the U7201 so confirm that this rail is indeed 0 volts @ coil and pin # 2.

5) voltage on P5VS4_DRVH (pin 1 of U7201) ? 0 volts means this side is not switching but may not be enabled.

Some of your voltages are correct for this component but the regulator is not on so post your readings from the above locations.

[waakye]

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

Hi mon2, thanks for replying. I cannot say how much I appreciate your help. Below are the results I measured

1) voltage readings @ 1 and 2 of the attached locations ? According to the calculator, this looks to be correct if the input voltage is around 12V.

= Voltage @ 1= 11.88VDC
Voltage @ 2= 1.92VDC

2) voltage on pin 21 (EN) / C7215 of U7201 ? (P3V3G3H_EN_SS)

= Voltage on pin 21 = 4.91VDC

3) voltage of P5VS4_EN1 (Q7210) = pin 4 of U7201 ?

= Voltage at pin 4 = 0VDC

4) voltage on L7220, pin 1 ? (PP5V_S4_REG) ? This mates with pin 2 of the U7201 so confirm that this rail is indeed 0 volts @ coil and pin # 2.

= Voltage on L7220 = 0VDC
Pin 2 of U7201 = 0VDC

5) voltage on P5VS4_DRVH (pin 1 of U7201) ? 0 volts means this side is not switching but may not be enab

= Voltage Pin 1 = 0VDC


Thanks again.
What should I be looking at now?

[mon2]

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

Post the voltages at:

1) pin 24 of U7201 (P3V3G3H_DRVH)

2) pin 27 of U7201 (P3V3G3H_DRVL)

If there is activity on the above 2 lines then Q7260 mosfet may be bad.

3) pin 1 of L7260 (PP3V3_G3H)

After the above, power down, meter in resistance mode, check and post the resistance to ground on pin 1 of L7260 (PP3V3_G3H).

The

PM_P3V3_G3H_PG
PM_PGOOD_REG_P5V_S4

lines are 'power good' status lines from this switching regulator.

Once the regulator actually enables and starts to switch out voltages - it will then monitor the feedback from the respective rails. This regulator offers 2 such rails with one on the left side and another on the right side. Each rail is checked against a threshold value and if found to be in the proper range, the PM_P3V3_G3H_PG / PM_PGOOD_REG_P5V_S4 status will change from a logic LOW (0 volts) to a logic HIGH (3v3 volts or close to this value). Currently you are @ 0 volts on these status lines because the rails are not turning on.

Will check if we still have the same mac mini in the building at work. If we do, will try to compare notes. Thought I heard that the client has not yet picked up the box and was wanting us to upgrade the SMD memory.

[waakye]

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

So I verify the voltages at the points below:
1) pin 24 of U7201 (P3V3G3H_DRVH)

= 0.0VDC

2) pin 27 of U7201 (P3V3G3H_DRVL)

= 0.0VDC


3) pin 1 of L7260 (PP3V3_G3H)

= 0.0VDC

Resistance at pin 1 of L7260 is 3.0M ohms and keeps going down and then up.

Thanks

[mon2]

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

The Mac mini was picked up last week so no longer have the access to the same logic board. Double check your soldering. Will study this more and share comments later.

The resistance is ok.

[mon2]

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

Review and try this idea:

https://superuser.com/questions/1264...n-after-outage

[mon2]

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

Your first post had a partial fan spin. Do you still have this now after the regulator replacement? If not, I am suspecting soldering. Once there is a partial fan spin, review this:

https://logi.wiki/index.php/A1347_20...arter_Fan_spin.

Noting a corrupt bios chip is possible. Personally have not repaired such a case but it should be well documented here in the forum.

[waakye]

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

Hi mon2,
Thanks again. I do not have quarter fan spin. But that is not due to the regulator that I replaced. I was trying different things way before you pitched in to help me. I guess I broke something way back when I was poking some components.

[waakye]

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

Good news and all thanks goes to mon2. Whenever you are in Montreal shout at me cuz you got a beer on me. I reviewed the area where I desolder the u7201 and one resistor was missing. I ordered that resistor and place it and all is well. MacMini is working now. The main issue was the defective U7201 chip.
Thanks mon2.

[mon2]

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

Good job! Glad that you did not give up