Temperamental Mac mini 2012 with start up issues.

weckart

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Nov 7, 2004
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I recently bought a late 2012 as a fuss-free light office use/web browsing machine and it is temperamental to say the least. On arrival it refused to power on. I went through all the most obvious tricks: resetting the SMC, changing the power cables, power points etc. After about 15 minutes of fussing and just before I was going to rebox it and return it, it booted.

Now, it works perfectly well once running but if I shut it down, it invariably refuses to start from cold.
I have found the best solution is to leave it unplugged for about half an hour then retry, resetting the SMC each attempt and after a few minutes of that it starts again.

I located the relevant ASD disc as the AHT had been wiped off by the seller and it passed every test. I have taken the unit apart and there doesn’t appear to be any obvious damage. The previous owner said it had had little use and the unit was very clean with barely any dust inside. It came with stock components. Also the screw heads indicated that nobody had done any work inside. I pulled out the PSU and tested it. It gave out 12V over all the relevant wires. The PRAM battery was still good giving the full 3V.

Is there any other obvious thing I have missed with this? I am loath to shut this machine down at any stage as it is an absolute pain to get going again. Has anyone ever encountered anything similar to this and did you find any solution besides returning the Mac Mini or scrapping the logic board?

Spec is the base 2.5GHz dual core processor with 4GB of RAM and a 500GB spinning hard drive.
 

DeltaMac

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Jul 30, 2003
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You said it won't power back on...
What DOES it do? Do you get a boot chime? Does the video turn on (and you see the Apple icon)
If neither of those things happen - does the fan come on at power on? Remove the bottom cover and watch the fan. Should be turning whenever power is on. (?)

Is there any difference if you simply do an SMC/NVRAM reset, like this:
Power off. Unplug everything, including power cord. Press and hold the power button for 10 seconds. Release.
Plug in the power cord, and keyboard/mouse, if those are wired USB. Display, too.
Press and release the power button, immediately holding Option-Command-P-R.
You should hear a boot chime. Keep holding the same 4 keys until you hear the boot chime 2 more times!
Release the keys, and let your mini boot up normally.
Be sure to set the boot drive in your Startup Disk pane.

Power issues that you are having might be the power supply (voltage drops under load might be the culprit). Be sure to replace that backup battery, even though it appears to test good for you.

Which video port are you using? I have two 2012 minis, and one has occasional issues with HDMI, but the MiniDisplayPort connection never has a problem. Maybe that can help you!
 

weckart

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You said it won't power back on...
By that I mean the Mini is apparently dead. No power light on the front, no sound from the fan or anything. Just totally unresponsive. I have tried plugging in the power cord at differing depths and angles just in case it is a contacts issue but nothing seems to make any difference. It only springs to life when it feels like it.

I have also tried powering it on with nothing attached, including the display and keyboard, again no difference.

Can it be the PRAM battery? There are very few Macs where a dead or dying PRAM battery could prevent the Mac from starting and the one in this one seems absolutely fine.
 

DeltaMac

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Try replacing the PRAM battery.

But, is there possibly a problem with the power button? Maybe it does not contact unless you press the button in exactly the "right" spot (?)
 

weckart

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Try replacing the PRAM battery.

But, is there possibly a problem with the power button? Maybe it does not contact unless you press the button in exactly the "right" spot (?)
Yeah, I thought that but there is very little play in that area, so I don’t think it is that, either. Replacing the PRAM is my next step. It is 7 years old and probably towards the end of its life. It is hard to get hold of BR2032 batteries cheaply, so I am hoping that the less solid voltages of the CR2032 won’t add to the boot up woes.
 

weckart

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Well, I replaced the PRAM battery and that fixed absolutely nothing. The Mini resolutely refused to spring into life. In the end, I left it alone for half an hour and then it cooperated with a chime. It is very frustrating.

Has anyone else ever had this happen before?
 

DeltaMac

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When it did start for you - were you able to do the PRAM/NVRAM reset (different from an SMC reset), using the steps that I listed above in post #2?)
What I am asking: when you can do a PRAM reset, and hear the boot chime, can you get more boot chimes while you continue to hold the same 4 keys?
 

weckart

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I replaced the battery. That would reset the PRAM. Nothing changed.
 

DeltaMac

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You are correct about replacing the PRAM battery, but the simple battery swapout may not necessarily settle everything related to the PRAM settings. That's why I suggest the keyboard PRAM reset, holding the reset keys through a minimum of 2 more boot chimes. It only takes a minute or so to try, and some Macs simply reset once, but don't respond in any way after the first reset cycle. That would indicate that something else is wrong, perhaps the boot rom, or something else on the logic board. If your Mac continues to reset while you hold the keys, then at least you can say that part seems to function.
 

weckart

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Not sure how any PRAM settings can be retained when the storage power is yanked but for completeness' sake I did the four finger salute and it chimed each time. I had run the ASD for this model and it couldn't find any fault on the logic board for what that is worth so I am completely stumped by the power issue. My best guess is that it must have something to do with the power switch but that isn't loose and as said, there is very little play in that area. It goes in a fraction of a millimetre and that is about it. No wobbling from left to right, which might mean the contacts are missed. Once up and running, it runs like a champ. Low temps and no glitches that I can see, so electronically, it does seem intact.

Thanks for persisting with this, though, I really appreciate that.
 

Fishrrman

macrumors P6
Feb 20, 2009
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I'm thinking, "bad power-on button", or something related thereto.

I'll offer a completely crude and kludgy "workaround" that you could try.
No promises even if you care to try it.
What I'd do is this:

Get a power strip with an on/off button.
Plug the Mini into the power strip.
Go to the energy saver pref pane and check the option to:
"Start up automatically after a power failure".

With things set up this way:
When it's time to power down the Mini, DO NOT USE the "shut down" item from the menu.
Instead, do this.
a. Close all apps and save all work.
b. Only the finder running
c. Reach down, and flip the power strip OFF
d. Mini will go dead.

When it's time to start up:
a. Reach down and turn ON the power strip
b. Does the Mini now spring back to life?
 
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weckart

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When it's time to start up:
a. Reach down and turn ON the power strip
b. Does the Mini now spring back to life?
Tried that. Nope no sign of life. Will leave it unplugged a while and hopefully it will start up again.
 

DeltaMac

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Can you try an SMC reset? (Shut off, then unplug the power cord, wait 20 seconds, then plug back in. One change that I would try is after unpugging the power cord, press and hold the power button for about 10 seconds, then try to boot)
If you STILL have to wait 10 minutes or so, then something is perhaps heating up, and MUST cool down on its own. I would lean toward the power supply. (some component refuses to support the initial power surge during boot)

I was thinking there is likely a workaround. Sleep your mini, don't shut it completely off - unless you are prepared to wait 30 minutes or so before you can boot up again.
 

weckart

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Nov 7, 2004
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Can you try an SMC reset? (Shut off, then unplug the power cord, wait 20 seconds, then plug back in. One change that I would try is after unpugging the power cord, press and hold the power button for about 10 seconds, then try to boot)

I was thinking there is likely a workaround. Sleep your mini, don't shut it completely off - unless you are prepared to wait 30 minutes or so before you can boot up again.
I recently bought a late 2012 as a fuss-free light office use/web browsing machine and it is temperamental to say the least. On arrival it refused to power on. I went through all the most obvious tricks: resetting the SMC, changing the power cables, power points etc. After about 15 minutes of fussing and just before I was going to rebox it and return it, it booted.
When resetting the SMC I held the power button in for 15 seconds each time while unplugged. Sleeping it rather than rebooting is what I am currently doing but it is annoying that if an errant application or website locks up the screen then I am stuck waiting for the machine to boot up again if it is forced to shut down to clear the lock up.
 

DeltaMac

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hmm.... I have two of those 2012 minis, and not ever seen a restart problem-- Well, I did have tricks with one that would power on, but not actually boot. Seemed to be associated with an HDMI connection, and changed to a mini DisplayPort connection fixed it for me. But, it would always power on (fan and boot chime, just wouldn't boot on up)
I guess you will need to experiment with actual hardware fixes:
swap power supply
swap logic board
repaste CPU heatsink (probably a waste of time for YOUR problem, but just something that others mention that might help with a possible heat issue.)
If you have a freeze, try popping the bottom cover off, and removing BOTH ram sticks, then try to power up immediately, just to see if you get an immediate power on, with error beeps (because of no ram installed). It won't boot further, but if there is an immediate response, you should try different ram sticks. I don't have good confidence in the ram being a problem in your instance, but it's a simple task to eliminate that as a fault.
 
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weckart

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hmm.... I have two of those 2012 minis, and not ever seen a restart problem-- Well, I did have tricks with one that would power on, but not actually boot. Seemed to be associated with an HDMI connection, and changed to a mini DisplayPort connection fixed it for me. But, it would always power on (fan and boot chime, just wouldn't boot on up)
I guess you will need to experiment with actual hardware fixes:
swap power supply
swap logic board
repaste CPU heatsink (probably a waste of time for YOUR problem, but just something that others mention that might help with a possible heat issue.)
If you have a freeze, try popping the bottom cover off, and removing BOTH ram sticks, then try to power up immediately, just to see if you get an immediate power on, with error beeps (because of no ram installed). It won't boot further, but if there is an immediate response, you should try different ram sticks. I don't have good confidence in the ram being a problem in your instance, but it's a simple task to eliminate that as a fault.

RAM has already been replaced with no improvement in obedience. This Mini is obstinately only getting out of bed when it feels like it. If it is a question of replacing either the PSU or the whole logic board then it is already an uneconomical repair considering the cost of those parts.

I suppose I was hoping for something along the lines of check this capacitor or resistor at position xyz etc.
 

Heat_Fan89

macrumors 6502a
Feb 23, 2016
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RAM has already been replaced with no improvement in obedience. This Mini is obstinately only getting out of bed when it feels like it. If it is a question of replacing either the PSU or the whole logic board then it is already an uneconomical repair considering the cost of those parts.

I suppose I was hoping for something along the lines of check this capacitor or resistor at position xyz etc.
You should drop Louis Rossman an email. His repair shop does board level repair and the guy is really good. I can tell because I used to do board level repair several decades ago. He could at least point you in the right direction. He might have an answer for you or you could ship him the Mini if you don't live in NYC. He has a YT Channel.

If I had to take a SWAG (scientific wild ass guess) i'd say you either have a marginal thermistor going bad in the PSU or possibly bad contacts on the power button.

Edit: If you feel up to it, you could remove the logic board from the case and check for cracked solder connections around the PSU area. Cracked solder connections can definitely produce these types of symptoms.
 
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weckart

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Edit: If you feel up to it, you could remove the logic board from the case and check for cracked solder connections around the PSU area. Cracked solder connections can definitely produce these types of symptoms.
Thanks, I will have a gander at that. The PSU is a sealed unit that connects to the logic board via a flat wire connection that is reasonably flexible. From what I can ascertain, the PSU seems to be working and providing a stable 12v power through all of the relevant wires. Possibly somewhere around the logic board some connection might be loose. If it is the power button, I don't think there is a simple way of getting to that without pulling the logic board apart and possibly ruining the switch altogether so that would be a last resort.

As for throwing Rossman an email, probably not. He must get thousands daily by now and I can't see how he is going to address them all. As I live in the UK, shipping to the US is also a non-starter. It would be cheaper to buy another MM.
 

Heat_Fan89

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Feb 23, 2016
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If you decide to check for cracked solder connections my advice just based from board level repair experience is that no matter how good your eyes are, you should use a LARGE magnifying glass and a good light (preferably fluorescent) to view the solder connections. You can easily be fooled by just using your own eyes to determine if you have a good or bad connections.
 
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