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Old Dec 25, 2012, 01:30 AM   #1
freebasen
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Join Date: Feb 2007
2006 Mac mini Possible fix for no power to logic board

I wanted to post this because I had a horrible time finding any information on how to repair. There are a lot of posts on random forums, but the only suggested solution seems to be to just replace the logic board. I didn't think the mini was worth the ~$200 for a new logic board. I can't guarantee all these minis are failing in the same way, but this seems worth a shot considering it will cost you next to nothing if you're handy with a soldering iron. Just locate the capacitor bank on the back side of the board, closest to the power jack. I got a 10uF reading from the good ones so I found replacements from a dead g5 imac board. Fair warning, these are really hard to get off the board. I don't think my iron was hot enough, but I made do. It's ugly, but it gets the job done. Hope this helps someone.
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Old Jan 17, 2013, 10:02 AM   #2
paulds65
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I am also trying to revive a 2006 mac mini. I have desoldered the same three capacitors. 2 of the capacitors show 10uF and one only a few nF. If I measure resistance over the capacitors still on the board I measure 0.0 Ohm (short circuit). Was this also the case with your mac mini? Are these 5 capacitors
all in parallel to get to 50uF?

Thanks,

Paul
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Old May 14, 2013, 11:49 AM   #3
jg321
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Add me to this club! I have two Mac Mini logic boards that have the same symptoms - no power at all. Power supply confirmed working with a G4 Mac Mini. As soon as you attempt to power either hosed logic board, the PSU doesn't even power the known working Mini, until the mains is removed and the PSU reset.

Any thoughts? I've multimetred the bank of caps mentioned in this thread and on one of the boards the caps are all short circuit. I've not removed them though, they're still on the board.

Any help would be appreciated.
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Old May 31, 2013, 01:44 PM   #4
laptopmd
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Hello !

I am in the same shoe, with a Mac Mini 2006 that doesn't turn on.

Checked the capacitors like the one on the first post, but they are working.

I have random values all around the logicboard... some 5.5 ohm , some 11 ohm, some 100ohm..
I have removed many and many capacitors but they are all working..

Unfortunately it looks impossible to find a schematic for this product, so we can reduce the range of where to find the short...
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Old Jun 1, 2013, 09:20 AM   #5
Omnius
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There is some information on this buried deep on this forum and elsewhere. Many, Many 2006-2007 owners have run into the same failed logic board issue over the last 2-3 years. It seems like it was a design defect that resulted in a shortened lifespan for an unusually high number of the minis.

If you can put together a strong guide, you may really have something. Minis from this generation with failed boards are selling on ebay and craigslist for very little in many cases. You might make a health profit for yourself in the process.
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Old Jun 2, 2013, 08:16 PM   #6
freebasen
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Sorry guys, I haven't check the forums here in a while. I have since revived 5 or the 7 mac minis I've found with the same problem. If you put your meter on the continuity test setting and check across the caps, you should not hear the "beep". If it beeps that means that the connection has been shorted somewhere, meaning one of the caps is bad. You can actually just pry off the bad cap and run without it once you've isolated it. So how to isolate which one is bad? Take a lab power supply and connect the black side to a common ground and the red side to the positive side of one of the capacitors. Very slowly sweep the voltage from 0 to ~5V. In between steps use your fingers to detect heat from the capacitors. The bad ones will heat up significantly. Remove them and the system should start right up. After you have verified it works, I would recommend replacing them with 10uF replacements.

----------

Also, yes these caps are connected in parallel.

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I should also mention that the bad cap(s) could be in any one of the 4 10uf banks.

----------

And finally, my personal mini has been running daily since December with no problems after applying this fix.
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Old Jun 6, 2013, 01:45 AM   #7
MacTech68
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Quote:
Originally Posted by laptopmd View Post
Unfortunately it looks impossible to find a schematic for this product, so we can reduce the range of where to find the short...
Yup. It's one of the schematics ( 820-1900-A ) I just CAN'T find (which would confirm what caps were originally used).

Quote:
Originally Posted by freebasen View Post
Sorry guys, I haven't check the forums here in a while. I have since revived 5 or the 7 mac minis I've found with the same problem. If you put your meter on the continuity test setting and check across the caps, you should not hear the "beep". If it beeps that means that the connection has been shorted somewhere, meaning one of the caps is bad. You can actually just pry off the bad cap and run without it once you've isolated it. So how to isolate which one is bad? Take a lab power supply and connect the black side to a common ground and the red side to the positive side of one of the capacitors. Very slowly sweep the voltage from 0 to ~5V. In between steps use your fingers to detect heat from the capacitors. The bad ones will heat up significantly. Remove them and the system should start right up. After you have verified it works, I would recommend replacing them with 10uF replacements.
----------
Also, yes these caps are connected in parallel.
----------
I should also mention that the bad cap(s) could be in any one of the 4 10uf banks.
----------
And finally, my personal mini has been running daily since December with no problems after applying this fix.
This entire thread has been excellent info.

I have a question or two before I proceed:

What voltage is present across these caps?

And are we certain they're all 10uf, 1206 sized ceramic caps?

I'm looking at just replacing them all since they seem to fail randomly.

BTW, I found another source confirming all that is mentioned here, just for reference:

http://blog.helpmymac.ru/?p=3585

EDIT: (much later) Found my culprit on the top side of the logic board in a bank of 4 next to the airport card connector. So that's at least FIVE locations they can be found. More to follow...
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Last edited by MacTech68; Jun 7, 2013 at 08:31 AM.
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Old Jun 13, 2013, 12:26 AM   #8
MacTech68
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The voltage across each bank of caps (top and bottom of the pcb) on my MacMini is 18.3 volts. The AC Adapter is rated at 18.5 volt output.

Be careful substituting these with 1206 sized 6.3, 10 or 16 volt caps.

You can get 1206 sized caps in 25, 35 and 40 volt. 35 volt sounds like a good choice but they're a little harder to get than the 25 volt. I'll guess that it's 25 volt ones that are failing.

Out of interest, my main board serial number label begins with "J58" and ends in "LDA" is finished goods 630-0494 and is code named M40B. This label is at the front edge adjacent to the battery holder, but is partially obscured by the felt, self adhesive airflow blocker. Maybe if enough of these labels are collected, and a pattern appears, we could establish a bad batch of caps - though it seems unlikely since the fault is fairly common.
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Last edited by MacTech68; Jun 13, 2013 at 12:34 AM.
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Old Jun 28, 2013, 05:03 PM   #9
laptopmd
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Here is my contribution.

I have found that the biggest short in my board was on this capacitor.
My mac will not even start up.

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But the problems are not finished yet.
My mac now show a white led blinking, i hear the superdrive that reset, and nothing else.

I have already tried to change ram modules... but nothing.
I measured another little short, near the southbridge... my feel is that this chip is shorted somewhere. When i have time, i will desolder it, reball and resolder back to the board to check if this is the failure...
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Old Oct 3, 2013, 02:50 PM   #10
enengi
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Unhappy Same problem with Mac mini late 2009

Although it is a bit off-topic I would like to note that I had the same sort of trouble with my late 2009 Mac mini. Fortunately, Google found this thread here ...

The Mac mini just stopped working completely. After disassembly and trying a new power supply cable I was certain that the cause had to be on the logic board.

I was lucky and found the defective ceramic capacitor (size 0805) on the bottom side straightaway. It caused a short on the 18.5 V supply rail. Because of that the external power supply went into shut-down (just as it is supposed to).

After removing the defective capaitor I noticed that one of the two green LEDs on the top side of the logic board came on again as soon as I plugged in the power supply cable (indicating the presence of 3.3 V standby power).

Since I wasn't able to get my hands on a 35 V ceramic capacitor I replaced the defective one with 1 uF / 50 V. Then I reconnected the power button and tried to power up the naked logic board. And it worked normally again (the other green onboard LED lit up), but only after I had put back in place the onboard battery (model BR2032).

Doing some voltage measurements I found out that there are quite a number of these capacitors connected to 18.5 V on both sides of the logic board. But I left them in place and reassembled my Mac mini which is now working fine again.
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Old Nov 14, 2013, 05:41 PM   #11
luchura
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testing the cap?

how exactly you test the cap, do you apply 0-5 volt of a 5 amp power supply, and check each for heat?. all my caps show a short, so one or more of them may be bad. Maybe I should just take away all of them and check out of the board?.
Thanks.
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Old Nov 26, 2013, 02:33 PM   #12
pekanut
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freebasen said:
If you put your meter on the continuity test setting and check across the caps, you should not hear the "beep". If it beeps that means that the connection has been shorted somewhere, meaning one of the caps is bad. You can actually just pry off the bad cap and run without it once you've isolated it. So how to isolate which one is bad? Take a lab power supply and connect the black side to a common ground and the red side to the positive side of one of the capacitors. Very slowly sweep the voltage from 0 to ~5V. In between steps use your fingers to detect heat from the capacitors. The bad ones will heat up significantly. Remove them and the system should start right up. After you have verified it works, I would recommend replacing them with 10uF replacements.
Have not tried it on my dead mini yet, though ...

Waiting for the christmas holidays to fix it.

Anyone can confirm this method ?

Thanx
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