iM 4,1-14,4 Looking for schematic diagram of 27" 2009-2011 iMac power supply, PA-2311-02A (liteOn)

[USB3foriMac]

Yes, I have shorted PS_ON pin to GND and nothing happen, +17v still unstable and the PSU is not turning on

I remember now. In my case, the feedback loop via the optocoupler was faulty, but this is likely not the same issue on each of these supplies.
Since the voltage was too low, I checked the feedback from the OpAmp, and I think (not sure any more, so long ago) that the signal was present at the OpAmp output but not at the optocoupler.
Do you have a scope to measure? If so, I can point you to the pin on the OpAmp. A normal multimeter is unlikely to give you meaningful result. I'll try later on mine (got a spare supply at hand) and update.

 

[man132]

I remember now. In my case, the feedback loop via the optocoupler was faulty, but this is likely not the same issue on each of these supplies.
Since the voltage was too low, I checked the feedback from the OpAmp, and I think (not sure any more, so long ago) that the signal was present at the OpAmp output but not at the optocoupler.
Do you have a scope to measure? If so, I can point you to the pin on the OpAmp. A normal multimeter is unlikely to give you meaningful result. I'll try later on mine (got a spare supply at hand) and update.

Unfortunately I dont have an oscilloscope

 

[USB3foriMac]

So I measured the "+17V" point vs GND (on the primary side), this is 14.62VDC, same whether PS_ONM is shorted to GND or open. That's probably correct, since the supply always delivers 12V as standby voltage.
So you can check that voltage for me.
I also measured at the Optocopulers. You need to be careful not to short any pins during measurement. It is not dangerous for you since the voltage is small, but since they affect the 12V voltage stability, you could potentially drive up the voltage to a level where some components could get damaged. I wouldn't try.

A->B is "PC300", C->D is PC301. So you can also measure on the top side if you prefer.
I check with a scope, and the voltage is basically stable when there is no load. From A (+) to B (-), I measure 1.07VDC. From C to D, I measure 0.88VDC.

I also check with a scope, and you can see the voltage in attached gifs. The AC fraction on A->B is only 40mVpp, so that I had to couple AC. This waveform would be elevated by 1.07VDC.
For C->D, the AC fraction is around 500mV, so I could couple DC and still see the signal. The DC offset is 0.88V.
If the optocouplers are degraded, the signal would go to either a maximum or minimum, in order to try to adjust the voltage.
So measure these two signals carefully.

Also, when PS_ON is not grounded, check the voltage on supply connector pin 4 (versus GND).
With PS_ON grounded, check the same, plus a voltage at pins 15 respectively 13 to GND. On a good supply, these would all be 12V. If your PS_ON FET is defect, pin 4 would still be 12V, but the others might be any voltage (normally remain at 0V, but could be floating).

 

[juanjodx]

You may look at the secondary right after the transformer. Check the diodes are ok there. What I believe is that the supply is trying to start up, but due to a short on the secondary, it shuts down again. There are other causes such as malfunctioning feedback circuit, but the feedback normally fails less often.

tkanks! just see your repply. i try and post the result

 

[man132]

So I measured the "+17V" point vs GND (on the primary side), this is 14.62VDC, same whether PS_ONM is shorted to GND or open. That's probably correct, since the supply always delivers 12V as standby voltage.
So you can check that voltage for me.
I also measured at the Optocopulers. You need to be careful not to short any pins during measurement. It is not dangerous for you since the voltage is small, but since they affect the 12V voltage stability, you could potentially drive up the voltage to a level where some components could get damaged. I wouldn't try.

A->B is "PC300", C->D is PC301. So you can also measure on the top side if you prefer.
I check with a scope, and the voltage is basically stable when there is no load. From A (+) to B (-), I measure 1.07VDC. From C to D, I measure 0.88VDC.
View attachment 2112372


I also check with a scope, and you can see the voltage in attached gifs. The AC fraction on A->B is only 40mVpp, so that I had to couple AC. This waveform would be elevated by 1.07VDC.
For C->D, the AC fraction is around 500mV, so I could couple DC and still see the signal. The DC offset is 0.88V.
If the optocouplers are degraded, the signal would go to either a maximum or minimum, in order to try to adjust the voltage.
So measure these two signals carefully.

Also, when PS_ON is not grounded, check the voltage on supply connector pin 4 (versus GND).
With PS_ON grounded, check the same, plus a voltage at pins 15 respectively 13 to GND. On a good supply, these would all be 12V. If your PS_ON FET is defect, pin 4 would still be 12V, but the others might be any voltage (normally remain at 0V, but could be floating).

Hi @USB3foriMac ,

Apologize for my late respond, I dont have time in weekdays to troubleshoot.

So, this afternoon, I able to conduct measurement, with below result:

PS_ON not grounded
A --> B : max 100mVDC
C --> D : max 100mVDC
pin 4 --> GND : 0 VDC
pin 15 --> GND : 0 VDC

PS_ON grounded
A --> B : max 160mVDC
C --> D : max 100mVDC
pin 4 --> GND : 0 VDC
pin 15 --> GND : 0 VDC

 

[USB3foriMac]

Hi @USB3foriMac ,

Apologize for my late respond, I dont have time in weekdays to troubleshoot.

So, this afternoon, I able to conduct measurement, with below result:

PS_ON not grounded
A --> B : max 100mVDC
C --> D : max 100mVDC
pin 4 --> GND : 0 VDC
pin 15 --> GND : 0 VDC

PS_ON grounded
A --> B : max 160mVDC
C --> D : max 100mVDC
pin 4 --> GND : 0 VDC
pin 15 --> GND : 0 VDC

the supply isn't regulating. I'd suspect something on your primary side isn't right.
I'd probably check once more the diodes and FETs on the primary side; I'd check the resistors at the Gate of the FETs; the diodes on the secondary side.
if that's not it, it could be a cold solder joint; it could be a dead capacitor; it could be a dead optocoupler.
There are just too many options here, and without a scope - and having checked the 'typical' components already - it will be very tough to find the actual issue.
I'm sorry I don't think I can be of further help in your case.

 

[LapoN]

Apologies for butting into this thread but I’m obviously missing something as I can’t figure out which is the PS_ON pin that needs to be shorted to ground to turn the power supply on.
Could someone explain which pin it is or point me to where I can find that out?
Thanks.

 

[USB3foriMac]

 

[LapoN]

That is awesome, USB3foriMac. I’ve been looking for that pin out diagram for ages. Thank you!

 

[zentropy]

This is a great thread! My 2011 iMac suddenly died today after something popped inside. I took it apart searching for a popped cap but all I could find was a blown fuse on the power supply board (pic). I measured it and it’s open circuit. I think something further down the circuit shorted and caused the fuse to blow, so I’m a little hesitant to just replace the fuse. But what do you experts think, does it make sense to replace the fuse and give it a shot? I only have a Fluke 87 multimeter at my disposal btw.

 

[USB3foriMac]

The fuse blew from overcurrent, particularly with that burn mark on the PCB as proof. It will blow again if you read it. Read the thread from the start, it explains how to check the relevant components. You should also follow the links to the 1 or 2 other related threads as these have a lot of relevant information as well. A (simple) multimeter is sufficient in most cases. There's a schematic somewhere for the input part, follow that and you might just find a MOSFET blown.

 

[zentropy]

Thanks, I started by checking the rectifier bridge and it seems it’s bad right off the bat. I’d appreciate it if anyone could verify that I measured it correctly.
Thanks!

 

[USB3foriMac]

The .5V seems ok, the reverse voltage should be OL. If a diode is blown in the rectifier, you'd see 0V between some pins (check all possibilities). If not, then the short is nearby, but not in the rectifier. Normally the FETs die, or diodes. It could also be a shorted capacitor. Take the schematic of the primary side and check each component after the rectifier until you find the short

 

[zentropy]

Thanks again, I think it’s the FETs as you mentioned. I managed to remove Q1 and Q3 and they both show a short between Drain and Source. (Actually I see a short in every possible combination between the 3 pins including the Gate.) I already got a bunch (10, min order) of the original fuse from Taiwan and I’ll see if I can source these MOSFETs locally. (If anyone needs a fuse, just let me know.)

USB3foriMac, thanks a lot for your help, I’ve learned a lot of electronics recently.

 

[jsalvadortrz]

Hello people,
Logged to share my issue with this PSU:

Failure: suddenly my Mac did not start anymore. Seems like some kind of over voltage at home...

I disassembled the PSU and found:

• Input fuse (6.3A blown)
• Diode bridge with 2 out of 4 diodes shorted
• MOSFETs from LLC stage short-circuited
• One power diode short-circuited (next to the polyester capacitors)
• 105k450VHF polyester capacitors blown (swollen, exploded)

I changed every single component. Also checked the diode and MOSFET of the PFC stage are OK.
Famous 10 ohms resistors were measured and OK as well...
I assembled back the PSU on my Mac, no more fuse getting blown, but no longer turning ON of my Mac so far.
I guess there's still sth wrong in my PSU I did not realize yet.

Did you guys found sth similar to mine???

Thanks in advance

 

[USB3foriMac]

Hello people,
Logged to share my issue with this PSU:

Failure: suddenly my Mac did not start anymore. Seems like some kind of over voltage at home...

I disassembled the PSU and found:

• Input fuse (6.3A blown)
• Diode bridge with 2 out of 4 diodes shorted
• MOSFETs from LLC stage short-circuited
• One power diode short-circuited (next to the polyester capacitors)
• 105k450VHF polyester capacitors blown (swollen, exploded)

I changed every single component. Also checked the diode and MOSFET of the PFC stage are OK.
Famous 10 ohms resistors were measured and OK as well...
I assembled back the PSU on my Mac, no more fuse getting blown, but no longer turning ON of my Mac so far.
I guess there's still sth wrong in my PSU I did not realize yet.

Did you guys found sth similar to mine???

Thanks in advance

Sounds you had a massive failure. Sorry to hear that. It is likely that the ICs are fried as well, but maybe you are lucky.
It might also be that a PCB track is burnt. Do you see any burn marks?
Further, some other resistors could have died; those responsible feeding supply voltage to the ICs, among others.
Best to measure most stuff without power, but you can do some measurements under power applied: check whether you have the high voltage DC at the high voltage capacitor. That would confirm some parts working.
Then check the supply voltage of the ICs.
Parts of the schematic is on page 1 or so.
As this is no simple single component issue, you need to judge whether this is worth your time.

 

[jsalvadortrz]

Hi guys, just came back to announce, iMac is back to live!

Just missed one of the 10 ohm resistors... just the one broken..
So apart to all I changed, I "adapted" this one with a TH one I had on basic DIY kits from my beginnings... and working!!

Surprised how strong these ICs are... With some MOSFET with G-S shorted, many MOSFET driver ICs got blown... (from my experience in power electronics)...

Thank you all for your big effort. I am an enthusiast and professional on power electronics, and you all did a gorgeous job reverse engineering this PSU!!

 

[tckoo1411]

View attachment 2119515

Hi Experts, would like to ask for your help. I have the liteon PSU in my imac 2011 27inch. The imac still able to power on, but a few observations:
1) After pressing the power button there will be a humming sound from the PSU.
2) If I insert 2 ram sticks, it will have the 3 long beep error. having one ram sticks boots fine.
3) The imac powers down randomly
4) I measured the 12V using a multimeter and all are stable at 12v. Measuring the SMB_ACDC_SDA and CSCL_RC, teh voltage fluctuates between 3.1v to 3.3v.

Would like to check where should I focus on? The secondary side capacitor, IC, etc? Thanks.

 

[USB3foriMac]

Hi Experts, would like to ask for your help. I have the liteon PSU in my imac 2011 27inch. The imac still able to power on, but a few observations:
1) After pressing the power button there will be a humming sound from the PSU.
2) If I insert 2 ram sticks, it will have the 3 long beep error. having one ram sticks boots fine.
3) The imac powers down randomly
4) I measured the 12V using a multimeter and all are stable at 12v. Measuring the SMB_ACDC_SDA and CSCL_RC, teh voltage fluctuates between 3.1v to 3.3v.

Would like to check where should I focus on? The secondary side capacitor, IC, etc? Thanks.

1. Depends on the sound. Can be vibration of a coil/transformer, or could be that your power cord doesn't have good contact and keeps sparking. Unplug the power cord to check whether there are burn marks on the contacts. If so, replace with new one.
Vibrating Transformer, nothing much you can do.
2. Bad contact. Use an eraser and rub over both sides of the ram stick until shiny. Then use alcohol to clean, wipe with a cloth. Do that for the other Ram stick, too.
If they are Elpida, they are originally supplied by Apple. Otherwise, they are third party. Some give problem if their timing parameters are not like original. You need "2400" speed.
Definitely a RAM problem.
3. Can be anything. Maybe see after you fixed the ram problem.
4. No point measuring on digital communication with a multimeter. 12V are fine. I wouldn't suspect your supply.

 

[tckoo1411]

1. Depends on the sound. Can be vibration of a coil/transformer, or could be that your power cord doesn't have good contact and keeps sparking. Unplug the power cord to check whether there are burn marks on the contacts. If so, replace with new one.
Vibrating Transformer, nothing much you can do.
2. Bad contact. Use an eraser and rub over both sides of the ram stick until shiny. Then use alcohol to clean, wipe with a cloth. Do that for the other Ram stick, too.
If they are Elpida, they are originally supplied by Apple. Otherwise, they are third party. Some give problem if their timing parameters are not like original. You need "2400" speed.
Definitely a RAM problem.
3. Can be anything. Maybe see after you fixed the ram problem.
4. No point measuring on digital communication with a multimeter. 12V are fine. I wouldn't suspect your supply.

Thanks for the reply.
1. to confirm it's from the PSU, I have swap out the cable, another good power supply, swap another LED back light power board. Only when using the liteon will I hear the buzzing sound.
2. Used known good ram from another working imac will result in 3 long beeps if I put 2 ram sticks in. If I put in 1 ram, everything works.
3. When using 1 ram stick, things will work for a awhile and the imac will power down randomly.
4. I was wondering if the secondary caps could be causing the buzzing or what component could be the suspect?

Thanks again.

 

[USB3foriMac]

Thanks for the reply.
1. to confirm it's from the PSU, I have swap out the cable, another good power supply, swap another LED back light power board. Only when using the liteon will I hear the buzzing sound.
2. Used known good ram from another working imac will result in 3 long beeps if I put 2 ram sticks in. If I put in 1 ram, everything works.
3. When using 1 ram stick, things will work for a awhile and the imac will power down randomly.
4. I was wondering if the secondary caps could be causing the buzzing or what component could be the suspect?

Thanks again.

I already mentioned what can cause the buzzing. Depends on the sound. Mostly vibration of transformer/coil. Caps don't make sound, but can cause voltage ripple which will cause reboots when load increases, such as suddenly running high CPU load.
The 3 beeps are RAM error. It's . If this always happens with the second slot, maybe check the second slot for corrosion or bent pins. Put the machine flat and take a look with a torchlight. I recommend again to treat the modules as already described previously. This is to ensure best possible contact, despite maybe your socket having corrosion. Treating the socket is far more difficult.
Again, check the RAM timing. "Working in one Mac" doesn't mean anything if the timing isn't as specified by Apple.

 

[hibananoe]

Hello Experts,
I really appreciate this forum and following since a while. I also have a defect PSU from iMac 27" A1312 LiteOn-Version and I logged in now, maybe someone can help me with an info:

I disassembled the PSU and found:

• Input fuse (6.3A blown)
• MOSFET on Heatsink 3 (HS3) with marking Q001 has a shortage
• rectifier is ok

I'm trying to replace these 2 parts, but I can't read the type of Q001 because of a molten housing (photo)

Could anyone tell me the type of this part? Maybe other hints how I can find the failure.

Thanks a lot!

 

[USB3foriMac]

The FET is 6R199P (IPA60R199CP). You can leave both the diode and the FET out, these are for power factor correction. If this is your only fault, the supply will work without these components.
There are several cases here where this indeed was the only fault. Make sure the primary FETs are not shorted, and the rectifier is ok. If so, you have good chances that it will work. If so, I wouldn't bother to replace the component. It's for the benefit of the power company and to protect their wiring.

 

[hibananoe]

The FET is 6R199P (IPA60R199CP). You can leave both the diode and the FET out, these are for power factor correction. If this is your only fault, the supply will work without these components.
There are several cases here where this indeed was the only fault. Make sure the primary FETs are not shorted, and the rectifier is ok. If so, you have good chances that it will work. If so, I wouldn't bother to replace the component. It's for the benefit of the power company and to protect their wiring.

Thanks a lot for that useful information - I will try and report!

 

[protocold]

does anyone know how the I 219A & EMC1404 circuit works? I have a ADP-310AF PSU with both of them blown [VS & Gnd are shorted], along with a blown TL432 (with marking T4DS)[cathode & anode shorted when chip is on the board but Cathode & VREF is not shorted to ground when chip is removed].

Right now the imac will blow high speed fan due to this. Would it be ok if i just change all 3 chips?