iMac 21.5 inch blows home fuse

[Rgrindheim]

Looks like you currently have a HDD in that iMac.

Seeing you have it open it would be a good idea to put a SATA III (6Gbps) SSD in it.

If the machine can be repaired an SSD will make it feel a lot faster, like having a significantly newer machine.

If the iMac cannot be repaired you would just open it up again and remove the SSD for use elsewhere.

Hi, thanks for your suggestion but my iMac has a Fusion Drive (1TB HDD and 128GB SSD). Also, it has 16GB memory so it’s pretty fast and satisfies my current needs. Perhaps a 1TB SSD one day in the future.?

I just checked – and this one is currently on sale here in Norway. Do you think it would be a good alternative? https://www.power.no/data-og-tilbeh...ddisk/samsung-860-evo-sata-ssd-1tb/p-1053247/

 

[USB3foriMac]

Hi, thanks for your suggestion but my iMac has a Fusion Drive (1TB HDD and 128GB SSD). Also, it has 16GB memory so it’s pretty fast and satisfies my current needs. Perhaps a 1TB SSD one day in the future.

R, it's really a good suggestion to use a large SSD instead, right now, since the thing is open atm. I doubt later you would open it just for that. The fusion drive is not a good performer under newer MAcOS systems. Despite being happy with what you have, you would be surprised how much snappier your system becomes by changing to SSD only (i.e. get rid of the fusion drive). Everything will be faster since the system does not need to wait for the motor to spin up and down, moving heads, etc.
You can get 1TB starting from ~60 EUR! If you want my personal recommendation, send a PM. Definitely worth it for this machine!

Also, let me know how your power supply progresses. I'd love to hear some good news on that.

 

[Rgrindheim]

There you go.
T2 is shorted, and of course this shorts out the circuit right after the rectifier. That's why you measure 0.6V at all sides of the rectifier. + and - are commoned by T2.
The glass fuse is too slow to blow, hence your house circuit breaker switches off much faster.
Just unsolder T2, or just cut the pins from the top side, and measure again. I'm fairly sure this is your only fault in the circuit and it will work again. There is no impact on function without having PFC. Main reason for PFC is to measure your power consumption more accurately.

Hi USBforiMac. I did as you suggested and cut the pins from T2. I then carefully connected the PSU to 230V AC input (using paper clips). Low and behold - no fuse blowout in the house.? In addition, I measured the voltage between + and - og the bridge rectifier and it showed 327V DC. Does this sound correct? I also tried measuring the output pin connections but couldn't get any sensible readings (just low mV flickering values). Perhaps the PSU needs to be connected to the iMac, and powered on in order to get pin out readings?

 

[Rgrindheim]

R, it's really a good suggestion to use a large SSD instead, right now, since the thing is open atm. I doubt later you would open it just for that. The fusion drive is not a good performer under newer MAcOS systems. Despite being happy with what you have, you would be surprised how much snappier your system becomes by changing to SSD only (i.e. get rid of the fusion drive). Everything will be faster since the system does not need to wait for the motor to spin up and down, moving heads, etc.
You can get 1TB starting from ~60 EUR! If you want my personal recommendation, send a PM. Definitely worth it for this machine!

Also, let me know how your power supply progresses. I'd love to hear some good news on that.

Maybe not such a bad idea after all if prices here in Norway are reasonable. I will start looking into it. Thanks.

 

[Rgrindheim]

R, it's really a good suggestion to use a large SSD instead, right now, since the thing is open atm. I doubt later you would open it just for that. The fusion drive is not a good performer under newer MAcOS systems. Despite being happy with what you have, you would be surprised how much snappier your system becomes by changing to SSD only (i.e. get rid of the fusion drive). Everything will be faster since the system does not need to wait for the motor to spin up and down, moving heads, etc.
You can get 1TB starting from ~60 EUR! If you want my personal recommendation, send a PM. Definitely worth it for this machine!

Also, let me know how your power supply progresses. I'd love to hear some good news on that.

I just checked SSD options and this one is currently on sale here in Norway. Do you think it would be a good alternative? https://www.power.no/data-og-tilbeh...ddisk/samsung-860-evo-sata-ssd-1tb/p-1053247/

 

[USB3foriMac]

Many use the Evo, many also use the Crucial MX500, which is probably a tad faster and better value compared to the Evo. You might also try to get your hands on a second hand 850 Pro. The Pro has superb lifespan, reliability and maximum speed. Here where I am they come with 10year warranty, so even a second hand would be left with more warranty than a new Evo or MX.
Larger SSDs are usually faster, looking at the low prices I'd recommend a 1TB.
AND: Once with SSD, your machine becomes a lot more attractive when reselling! Once both machines run, you sell the one you don't like as much.

I'm confident the power supply is ok. The 12V are only on if the logic board has given the signal to power on. There might be a standby voltage at one of the pins on the small connector. Another pin is a startup input to get the supply working. I do not know the pinning so best to just put into the machine.

 

[wilberforce]

I'm confident the power supply is ok. The 12V are only on if the logic board has given the signal to power on. There might be a standby voltage at one of the pins on the small connector. Another pin is a startup input to get the supply working. I do not know the pinning so best to just put into the machine.

Pretty interesting seeing you two work together to fix a power supply circuitry via a forum thread. Interesting what one can do with a multimeter and some persistence.
My story is that when I was sailing around the world, my ham radio (which I used for worldwide communication) failed when I was 1000+ miles from land in the Pacific Ocean - at least three weeks sailing from any repair facility. So, even though I am not an electrical engineer, but armed with a schematic and a multimeter I disassembled the radio and started checking every component on every circuit board, figuring I had nothing to lose and plenty of time. After about two days I found one open resistor. So I found another resistor with the same color-coding in a cassette player, and soldered it in. Amazingly, it worked, and I was able to communicate again!
Sorry for the off-topic digression.

 

[Rgrindheim]

Many use the Evo, many also use the Crucial MX500, which is probably a tad faster and better value compared to the Evo. You might also try to get your hands on a second hand 850 Pro. The Pro has superb lifespan, reliability and maximum speed. Here where I am they come with 10year warranty, so even a second hand would be left with more warranty than a new Evo or MX.
Larger SSDs are usually faster, looking at the low prices I'd recommend a 1TB.
AND: Once with SSD, your machine becomes a lot more attractive when reselling! Once both machines run, you sell the one you don't like as much.

I'm confident the power supply is ok. The 12V are only on if the logic board has given the signal to power on. There might be a standby voltage at one of the pins on the small connector. Another pin is a startup input to get the supply working. I do not know the pinning so best to just put into the machine.

I’ll await putting everything together until I decide on a new SSD - hopefully next week. I may start a new thread with regard to swapping a HDD drive to SSD on a fusion iMac. If both drives are SSD, I assume there is no need for the drives being ”fused” together. Would be interesting to hear what others have experienced here. Think I’ll start that thread today.?

 

[USB3foriMac]

Pretty interesting seeing you two work together to fix a power supply circuitry via a forum thread. Interesting what one can do with a multimeter and some persistence.
My story is that when I was sailing around the world, my ham radio (which I used for worldwide communication) failed when I was 1000+ miles from land in the Pacific Ocean - at least three weeks sailing from any repair facility. So, even though I am not an electrical engineer, but armed with a schematic and a multimeter I dissembled the radio and started checking every component on every circuit board, figuring I had nothing to lose and plenty of time. After about two days I found one open resistor. So I found another resistor with the same color-coding in a cassette player, and soldered it in. Amazingly, it worked, and I was able to communicate again!
Sorry for the off-topic digression.

Thanks for your comments.
I wish more people would (be able to) repair products and companies would produce repairable products in the first place (that includes providing documentation), for the benefit of the environment and for saving valuable resources.

 

[Rgrindheim]

Pretty interesting seeing you two work together to fix a power supply circuitry via a forum thread. Interesting what one can do with a multimeter and some persistence.
My story is that when I was sailing around the world, my ham radio (which I used for worldwide communication) failed when I was 1000+ miles from land in the Pacific Ocean - at least three weeks sailing from any repair facility. So, even though I am not an electrical engineer, but armed with a schematic and a multimeter I dissembled the radio and started checking every component on every circuit board, figuring I had nothing to lose and plenty of time. After about two days I found one open resistor. So I found another resistor with the same color-coding in a cassette player, and soldered it in. Amazingly, it worked, and I was able to communicate again!
Sorry for the off-topic digression.

Thanks for your comments. USBforiMac deserves praise for his valuable knowledge. Nice to know people who like fixing things.?

 

[Rgrindheim]

Eureka! I finally got around to reassembling my iMac with the «reworked» PSU as instructed by USBforiMac.?? The iMac came to life and seems to be working like it did before the problem arose in April.? The next phase will be swapping the HD for a new SSD. I will let folks know how that goes on the other thread I created.

 

[nicocorradini]

Hi! I’m having exactly the same problem with my A1418. Sadly, my electronic skills are not enough to follow USB3foriMac instructions. Also, my multimeter doesn’t have diode mode Can you, please, post a photo or image of the component you removed to get the PSU working again?

I already took the power supply away from my iMac, and buying a new one in Argentina is a really difficult job... Thanks!

 

[Rgrindheim]

Hi nicocorradini. My electronic skills are not great either but thanks to USB3foriMac I managed to get my PSU working by removing the connection to the MOSFET shown in the attached photos. Hope this helps.

 

[Rgrindheim]

Hi! I’m having exactly the same problem with my A1418. Sadly, my electronic skills are not enough to follow USB3foriMac instructions. Also, my multimeter doesn’t have diode mode Can you, please, post a photo or image of the component you removed to get the PSU working again?

I already took the power supply away from my iMac, and buying a new one in Argentina is a really difficult job... Thanks!

Hi nicocorradini. My electronic skills are not great either but thanks to USB3foriMac I managed to get my PSU working by removing the connection to the MOSFET shown in the attached photos. Hope this helps.

 

[Jumme_Cph]

Hi, thanks for your suggestion but my iMac has a Fusion Drive (1TB HDD and 128GB SSD). Also, it has 16GB memory so it’s pretty fast and satisfies my current needs. Perhaps a 1TB SSD one day in the future.?

I just checked – and this one is currently on sale here in Norway. Do you think it would be a good alternative? https://www.power.no/data-og-tilbeh...ddisk/samsung-860-evo-sata-ssd-1tb/p-1053247/

VERY happy to hear you got your problem solved. It’s a nice Mac and reviving it for another couple of years was worth the trouble, IMO! Great job. ????

Now, since I somehow was not notified of the last series of replies here, I didn’t get to give an vital input;

You DONT wanna exchange your SATA HDD with a SATA ssd. You wanna completely remove it, because, since you have a fusion drive, means you have a PCIe/NVMe socket on your motherboard.

THIS is the drive you wanna upgrade, to the most expensive disk you can afford. It’s many times faster than the SATA ssd/HDD. And then remove the old HDD all together, and leave the slot empty.
This is both due to speed and heat dissipation.

Anyway. Happy to hear you have a working Mac.

 

[Rgrindheim]

VERY happy to hear you got your problem solved. It’s a nice Mac and reviving it for another couple of years was worth the trouble, IMO! Great job. ????

Now, since I somehow was not notified of the last series of replies here, I didn’t get to give an vital input;

You DONT wanna exchange your SATA HDD with a SATA ssd. You wanna completely remove it, because, since you have a fusion drive, means you have a PCIe/NVMe socket on your motherboard.

THIS is the drive you wanna upgrade, to the most expensive disk you can afford. It’s many times faster than the SATA ssd/HDD. And then remove the old HDD all together, and leave the slot empty.
This is both due to speed and heat dissipation.

Anyway. Happy to hear you have a working Mac.

Yes, thanks to the repair, I am now the happy owner of 2 working iMacs. I have set up one of the iMacs with ”Parallels” in order to run Windows when necessary. Interesting to hear your recommendation regarding NVMe SSD. I wasn’t aware of this at the time and I did buy the Samsung SSD and installed it. I’m using the 128 SSD to store backup of OS etc. Everything is working fine but I may look into a NVMe SSD for future upgrade of one of the iMacs. Thanks for the advice and getting back to me.

 

[Jumme_Cph]

Yes, thanks to the repair, I am now the happy owner of 2 working iMacs. I have set up one of the iMacs with ”Parallels” in order to run Windows when necessary. Interesting to hear your recommendation regarding NVMe SSD. I wasn’t aware of this at the time and I did buy the Samsung SSD and installed it. I’m using the 128 SSD to store backup of OS etc. Everything is working fine but I may look into a NVMe SSD for future upgrade of one of the iMacs. Thanks for the advice and getting back to me.

Do me a favour and post the excact model name of your iMac’s?
Is it Early 2013, or Late 2013..?

 

[Rgrindheim]

Do me a favour and post the excact model name of your iMac’s?
Is it Early 2013, or Late 2013..?

iMac (21.5-inch, Late 2012)

 

[sotea]

Hi everybody. Got exactly the same problem (on exactly the same card) on my iMac late 2013.

- Home fuse blew while it was switched on, discovered it was actually my PSU.
- PSW fuse was blown as well, I replaced it and I had PSU keeping home fuse blowing once connected again.
- Followed this thread, discovered T2 was shorted, cut it out from the PSU.

Actually, no problem anymore on my home fuse but... still not working (I've actually verified voltage directly on the PSU, no output at all).

Bridge rectifier and all other MOSFET look good, checked all capacitors as well and nothing apparently wrong, no evident sign of damage.
Any idea/suggestion from anybody?

Thanks

 

[PauMoreno]

Hi everybody. Got the same problem on my iMac late 2013.
Thanks to Rgrindheim and all the people here I have repaired my iMac.
I tried cutting Mosfet out from the PSU and no more home fuse blowing but iMac still not working.
I bought a refurbished/used PSU at AliExpress (yes, I know, but No Risk No Fun), replace it and my iMac is working fine again (I hope for a long time)!!
So thanks again to everybody here!

 

[PauMoreno]

Hi everybody. Got exactly the same problem (on exactly the same card) on my iMac late 2013.

- Home fuse blew while it was switched on, discovered it was actually my PSU.
- PSW fuse was blown as well, I replaced it and I had PSU keeping home fuse blowing once connected again.
- Followed this thread, discovered T2 was shorted, cut it out from the PSU.

Actually, no problem anymore on my home fuse but... still not working (I've actually verified voltage directly on the PSU, no output at all).

Bridge rectifier and all other MOSFET look good, checked all capacitors as well and nothing apparently wrong, no evident sign of damage.
Any idea/suggestion from anybody?

Thanks

My suggestion is to get a new/refurbished/used PSU and try. I was afraid to be a mainboard problem when cutting out MOSFET did not work but replacing PSU was the solution.

 

[rjavierr]

same problem here, blown fuse 6,3A. Done cut terminals on mosfet 2, new fuse (with a bigger size fuse and soldering cables to the pins of the board, because is what I had at home) and still don't start. No light on the pcb. ( I´ll try a new power supply. thanks anyway!

 

[pankajet]

All,

I do have same supply adp 185 ( from mac a1418) has gone bad. I have replaced PFC FET, NCP1605 but supply still not working. No other shorts is found on board.
Few observations:

1. VCC on NCP1605 is changing ( 8v - 15V), not stable.
2. PFC_ok is just 1.6v to 2V.
3. Voltage after SJ8C diode is ˜400V; means has happned.
4. IC L6599 - vcc is again dropping ( ˜7v to 13v).


Any sugestion what to check next . Why vcc is not stable ?

Power supply blowe the home fuse at mac power-up and then got damaged.

 

[Jumme_Cph]

All,

I do have same supply adp 185 ( from mac a1418) has gone bad. I have replaced PFC FET, NCP1605 but supply still not working. No other shorts is found on board.
Few observations:

1. VCC on NCP1605 is changing ( 8v - 15V), not stable.
2. PFC_ok is just 1.6v to 2V.
3. Voltage after SJ8C diode is ˜400V; means has happned.
4. IC L6599 - vcc is again dropping ( ˜7v to 13v).


Any sugestion what to check next . Why vcc is not stable ?

Power supply blowe the home fuse at mac power-up and then got damaged.

You would have to ask this in a board repair forum. Or Electronics forum.

Most here only do part swapping, eg. full PSU unit, AFAIK.

 

[USB3foriMac]

All,

I do have same supply adp 185 ( from mac a1418) has gone bad. I have replaced PFC FET, NCP1605 but supply still not working. No other shorts is found on board.
Few observations:

1. VCC on NCP1605 is changing ( 8v - 15V), not stable.
2. PFC_ok is just 1.6v to 2V.
3. Voltage after SJ8C diode is ˜400V; means has happned.
4. IC L6599 - vcc is again dropping ( ˜7v to 13v).


Any sugestion what to check next . Why vcc is not stable ?

Power supply blowe the home fuse at mac power-up and then got damaged.

If the home fuse blew, there was excess current, which normally comes from shorted FET on primary side, either PFC or at the transformer. Since you already swapped the PFC FET, I'd take another look or two at the transformer FET. If they are really not shorted, chech the diodes on the secondary of the transformer.
Look again and again at FETs and diodes, one of them must be either shorted. Check not only drain to source but also Gate to drain/source. Remember the parasitic diode that you will measure at D-S.