I got a 2009 iMac 27" PSU that would stopped working, I could get it to occasionally come on and then it would stay on for as long as you wanted but power off would make it appear dead again. I took the PSU out and noticed some bulging capacitors. 2 x 2200uF and 6 x 1000uF. I replaced these caps and I was sure this would resolve my issue but it didn't :-(
I have a similar PSU and it keeps blowing fuses in the plug and it also blew the little on-board fuse next to the AC input connector. That little round thing next to the fuse appears to be a dead short circuit. Is it a capacitor or something else? Anyone know?
Really useful - I don't have a dummy load but I'm getting 12V when connected the way you have done it so I'm assuming that means power supply is probably OK, which means my logic board has failed :0(
Hi I have a 2017 5k iMac. As it was very dusty inside and therefore getting very hot i´ve torn it apart, cleaned everything, put new thermal paste on cpu and gpu and put everything togehter. Actually not a hard job. But right now it wont turn on. I left the display off to do some testing. LED #1 is lighting up. LED #2 doesn´t. I already checked the power button with a multimeter and it works properly. Next step was to replug all the connectors and while doing that i checked the pins. Everything seems to be right. Now i´d like to test the psu. Do you have something like a pinout scheme for the power cables? So i could check with the multimeter. Or do you have any other tips what it could be?
Old comment but I'm in the same boat. Took mine apart to replace a failing hard drive. Made the mistake of taking the logic board out to apply new thermal paste. Put it all back together with a new SSD and it won't power on. LED 1 is lit. Power switch is good. Just nothing. Did you ever find a solution?
I am also on the very same scenario. Late 2012 27 inch iMac with Fusion Drive. Wanted to do away with the Fusion Drive so I stripped it all out and whilst the logic board was out I’ve re-applied thermal paste and upgraded the ssd blade and also removed the old 3.5 inch drive and fitted an SSD. Put it all back together and nothing but LED #1 I’m thinking if I’ve done something to the PSU or the power button.
Yes. All the iMac needs is 12V and a lot of amps. So if you feed it that, it should work. It might however be upset, if you remove the power supply. So I would advise to leave it in and feed 12V to the output of the power supply.
Did u find this answer? I got a late 2015 with a Pa 1311 2a2 inside. But i can get my hands on 2a1 , someone tell me pls what works toghter what not...
How you discharge the capacitors after this test before safe to handle to put back into the imac? I tried shorted the power on switch for 1 minutes, multimeter still showing power in the capacitor pins. And last resort as it is faulty power supply no 12V and not going to repair it, i use a plier to short the capacitors pins and WHOA it give a big sparks, scare the shit out of me.
This Power Supply is always on, it always outputs 12V and it should always be able to deliver 25Amps. The Power-Button just controls the Mainboard through the smaller connector going to the mainboard. The reason, you see the voltage drop at 2-3A load is you less than ideal connection. I am surprised that you own an electronic load and did not realize that.
Hey mate I have a problem with my iMac 2013 power supply which is identical to this one. When I connect up power the fuse blows. What would you suggest? Needs to be replaced?
Luke Roberts Which fuse is blowing? The one in the mains lead? Circuit breaker in fuse box? The power supply has its own fuse that should blow before the mains lead. Can you give me a bit more detail please?
Luke Roberts I’ve repaired a few Apple supplies and in my experience it’s usually either the bridge rectifier that short circuits and/or the main switching MOSFET so that’s where I’d recommend you start. The fact it’s blowing the primary side fuse means it’s most likely in that area.
That's not something that I've heard about personally. I mean I'm still alive and I got proper down and dirty with that supply, which was at mains voltage for my testing...
Probably because the iMacs power supplies are unshielded like other PC power supplies. The deadly part is probably when you recently used the iMac, unplugged it and haven’t discharged the capacitors yet when you’re trying to operate on them. If it isn’t any of these reasons then I’m interested what else would make them dangerous.
Linux Mint I tore down an iMac and rebuilt mine this past winter. Discharged them the way you are supposed to but didn’t go anywhere near those exposed parts! Lol
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I got a 2009 iMac 27" PSU that would stopped working, I could get it to occasionally come on and then it would stay on for as long as you wanted but power off would make it appear dead again. I took the PSU out and noticed some bulging capacitors. 2 x 2200uF and 6 x 1000uF. I replaced these caps and I was sure this would resolve my issue but it didn't :-(
I have a similar PSU and it keeps blowing fuses in the plug and it also blew the little on-board fuse next to the AC input connector. That little round thing next to the fuse appears to be a dead short circuit. Is it a capacitor or something else? Anyone know?
Really useful - I don't have a dummy load but I'm getting 12V when connected the way you have done it so I'm assuming that means power supply is probably OK, which means my logic board has failed :0(
Usually, these power supplies fail hard-core when they fail. So if yours is still giving you 12V out, it's most likely fine.
Hi
I have a 2017 5k iMac. As it was very dusty inside and therefore getting very hot i´ve torn it apart, cleaned everything, put new thermal paste on cpu and gpu and put everything togehter.
Actually not a hard job.
But right now it wont turn on. I left the display off to do some testing.
LED #1 is lighting up. LED #2 doesn´t. I already checked the power button with a multimeter and it works properly.
Next step was to replug all the connectors and while doing that i checked the pins. Everything seems to be right.
Now i´d like to test the psu. Do you have something like a pinout scheme for the power cables? So i could check with the multimeter.
Or do you have any other tips what it could be?
Old comment but I'm in the same boat. Took mine apart to replace a failing hard drive. Made the mistake of taking the logic board out to apply new thermal paste. Put it all back together with a new SSD and it won't power on. LED 1 is lit. Power switch is good. Just nothing.
Did you ever find a solution?
I am also on the very same scenario.
Late 2012 27 inch iMac with Fusion Drive. Wanted to do away with the Fusion Drive so I stripped it all out and whilst the logic board was out I’ve re-applied thermal paste and upgraded the ssd blade and also removed the old 3.5 inch drive and fitted an SSD.
Put it all back together and nothing but LED #1
I’m thinking if I’ve done something to the PSU or the power button.
Is it possible to buy pass the mains power board and run it in a camper from off a 12 volt supply and without having to use a step up power transfer
Yes. All the iMac needs is 12V and a lot of amps. So if you feed it that, it should work. It might however be upset, if you remove the power supply. So I would advise to leave it in and feed 12V to the output of the power supply.
what is the different of pa-1311-2a1 vs pa-1311-2a2 , can pa-1311-2a1 use for late 2015 imacs ?
Did u find this answer?
I got a late 2015 with a
Pa 1311 2a2 inside. But i can get my hands on 2a1 , someone tell me pls what works toghter what not...
How you discharge the capacitors after this test before safe to handle to put back into the imac? I tried shorted the power on switch for 1 minutes, multimeter still showing power in the capacitor pins.
And last resort as it is faulty power supply no 12V and not going to repair it, i use a plier to short the capacitors pins and WHOA it give a big sparks, scare the shit out of me.
Use a big resistor with clip leads
Can I get 24v output from the power supply?
Nope.
This Power Supply is always on, it always outputs 12V and it should always be able to deliver 25Amps. The Power-Button just controls the Mainboard through the smaller connector going to the mainboard.
The reason, you see the voltage drop at 2-3A load is you less than ideal connection. I am surprised that you own an electronic load and did not realize that.
Hi. Very impressive job you did there. Do you do IMac repairs for a living?
Nope, I was just given this dead 5k, i7 iMac and wanted to bring it back to life. I'm an enthusiastic amateur and do IT support for my real job.
Hey mate I have a problem with my iMac 2013 power supply which is identical to this one. When I connect up power the fuse blows. What would you suggest? Needs to be replaced?
Luke Roberts Which fuse is blowing? The one in the mains lead? Circuit breaker in fuse box? The power supply has its own fuse that should blow before the mains lead. Can you give me a bit more detail please?
The Equalizor correct! The fuse on the power supply. It’s a T3.6A 250V I’m in Australia so I don’t have a fuse in the lead
The Equalizor it is also shorting out the circuit breaker in the fuse box on the house
Luke Roberts I’ve repaired a few Apple supplies and in my experience it’s usually either the bridge rectifier that short circuits and/or the main switching MOSFET so that’s where I’d recommend you start. The fact it’s blowing the primary side fuse means it’s most likely in that area.
The Equalizor ok great thanks so much for your help
What’s the story with the iMac power supplies being dangerous and can kill?
That's not something that I've heard about personally. I mean I'm still alive and I got proper down and dirty with that supply, which was at mains voltage for my testing...
Probably because the iMacs power supplies are unshielded like other PC power supplies. The deadly part is probably when you recently used the iMac, unplugged it and haven’t discharged the capacitors yet when you’re trying to operate on them. If it isn’t any of these reasons then I’m interested what else would make them dangerous.
Linux Mint I tore down an iMac and rebuilt mine this past winter. Discharged them the way you are supposed to but didn’t go anywhere near those exposed parts! Lol