IMac 21.5" 2011 A1311 problem - help needed please!

[funkuncut]

I connected an external dvd drive to my iMac by USB and stupidly used the wrong power supply, giving it 12v instead of 5v.
My iMac is now dead.
Is it likely that I have damaged the logic board and/or PSU?
Can anyone advise me on how to proceed now?
I can get another logic board and/or PSU and replace it, but I don't know what problems to look out for if I do that - will I be able to restore from a Time Machine backup?
What can I do if the replacement board has a firmware password?
If there is a hint of desperation in this, it's an indication of my level of panic!
Thanks in advance.....

 

[jasongoldworthy]

hi there

its likely the logic board has died hence why its no longer booting.

I doubt you have killed the PSU

and you wouldn't need to do a time machine restore as the hard drive will just boot as it did before.

if there is a firmware password then that will be an issue and something that should be turned off before the machine was decommissioned.

logic board swopping is easy but there are many tutorials online.

any more questions please ask.

 

[lclev]

Wow, I find it amazing an external fried your iMac. Usually the wrong PS on an external fries the external. But anything can happen. Can I assume you removed all the external devices, reset the SMC and NVRAM just in case that might help?

If you need a "how to" for the SMC and NVRAM: How to reset NVRAM, PRAM, SMC on a Mac | Macworld

Lisa

 

[funkuncut]

Thank you! I'll try swapping the logic board - I imagine it would be a good idea to get exactly the same one? Is the number on the side of the board only visible once removed?
Sorry if these are stupid questions, but I don't have much experience, although I did take it apart to fit an SSD a few years ago, and I'm confident enough to change the board....
Thanks again!

 

[funkuncut]

Thanks Lisa - I wrote my reply before seeing your post! I did disconnect everything and try again, but not the SMC and NVRAM reset. I'll try that once I've read the 'how to' - thanks again!

 

[funkuncut]

No luck - it's dead, dead, dead! I'll investigate a logic board in the morning....

 

[krs]

I have to agree with Lisa, I don't understand how you killed the iMac
You said:

I connected an external dvd drive to my iMac by USB and stupidly used the wrong power supply, giving it 12v instead of 5v.

Where did you connect the 12 volt supply?
To the exyernal DVDdrive? or to the iMac?
When I connected a DVD drive to my Mac there was no additional power required - power for the external drive came from the Mac's USB port.

 

[funkuncut]

The external drive has a USB connection and a round socket for power. I haven't used it for a long time, but I think it has another lead which is USB one end and round power plug the other. I only had one free USB port on the Mac, so I used that, since some drives don't work if connected to a Belkin powered hub I have.
I thought I was plugging in a 5v supply from a wall wart, but it was 12v.
Maybe it was coincidence? It's definitely dead, and I have checked the mains lead for voltage, and it's ok.
Is there anything else I can check?

 

[funkuncut]

I've checked the power button - it's ok
When I connect the mains lead, the left led in the row of 4 lights up.
I can't see any bulging or blown capacitors, so I'm not sure what else to check.
The logic board is 820 2641 A. Does a replacement need to be the same code, or will others fit? (if replacing the logic board is the next step....)

 

[jasongoldworthy]

I've checked the power button - it's ok
When I connect the mains lead, the left led in the row of 4 lights up.
I can't see any bulging or blown capacitors, so I'm not sure what else to check.
The logic board is 820 2641 A. Does a replacement need to be the same code, or will others fit? (if replacing the logic board is the next step....)

Stick with the same logic board if you can based on the numbers.

here in the uk the boards are easy sourced so try eBay for one if you can.

 

[krs]

The external drive has a USB connection and a round socket for power. I haven't used it for a long time, but I think it has another lead which is USB one end and round power plug the other. I only had one free USB port on the Mac, so I used that, since some drives don't work if connected to a Belkin powered hub I have.
I thought I was plugging in a 5v supply from a wall wart, but it was 12v.
Maybe it was coincidence? It's definitely dead, and I have checked the mains lead for voltage, and it's ok.
Is there anything else I can check?

The most I would have expected in that case would have been a damaged USB port on the iMac...and even that is iffy.
The power for the DVD drive, where you connected 12 volts instead of 5 volts, should not go anywhere near the iMa, much less kill it completely.
I assume you disconnected all the iMac peripherals before you tried booting up.

PS: Glad to hear that iMac logic boards are easy to source in the UK.

 

[jasongoldworthy]

I agree with krs I would be thinking the same that normally the circuit should be separate so the 12v don't go up the USB ports.

but if your getting one light on the logic board its not dead yet.

have you tried unplugging the machine holding the power button for 30 seconds and plugging it in again ?

 

[funkuncut]

It doesn't seem logical that 12v on an external drive would kill the iMac, but it's not my area of expertise (not sure what is, really!) and maybe it's just coincidence?
I have tried the unplugging and holding the power button - still the same.
A bit of research seems to show that one led on the logic board is not necessarily an indication that the PSU is working 100%, just that there is mains connected - is that right?
I'm in the UK, and it looks like I can get a logic board for less than £50, so it may be worth a punt (although it also looks like I could get another iMac of the same vintage for £100 - but I'd rather repair than replace...)
I use it mainly for music and making digital copies of vinyl, and I'm very happy with it - don't need anything faster or fancier, so I'd like to be able to fix it!

 

[funkuncut]

I have also been trying it with nothing at all connected - no drives, not even keyboard. There are usually two external drives permanently connected: one by USB for media storage, and one by Firewire for backups. Both those are fine.

 

[jasongoldworthy]

It doesn't seem logical that 12v on an external drive would kill the iMac, but it's not my area of expertise (not sure what is, really!) and maybe it's just coincidence?
I have tried the unplugging and holding the power button - still the same.
A bit of research seems to show that one led on the logic board is not necessarily an indication that the PSU is working 100%, just that there is mains connected - is that right?
I'm in the UK, and it looks like I can get a logic board for less than £50, so it may be worth a punt (although it also looks like I could get another iMac of the same vintage for £100 - but I'd rather repair than replace...)
I use it mainly for music and making digital copies of vinyl, and I'm very happy with it - don't need anything faster or fancier, so I'd like to be able to fix it!

based on what you tried id say its more than likely the logic board is bad.

the 1st light on the logic board means trickle voltage of 5v is detected.

if you press the power button do the fans even twitch ?

and on the repairing im the same id rather fix it than bin it and at £50 you can't go wrong.

one more thing you could do if you can get a whole machine for £100 you could always repair yours and keep the rest for spare parts.

as yours could be in better condition than the one you can get for £100 if that's an option

 

[Raz0rEdge]

Depending on the protections of the external drive, if it got more than it could handle, it should've blown a bunch of capacitors on itself, but if the protection is bad, then that power has to go somewhere and it would likely go down the USB cable.

Since USB is able to carry power (up to 5v), you most definitely have blown out your USB port for sure. I would imagine that the iMac has better protection against surges of power and should have caps in place to be blown out before it affects the rest of the logicboard.

Now, going to 12v is more than just a simple surge, so you must have blown things farther up the stream than just the USB port.

You can open up the iMac, and begin from the USB port you were plugging into and see if you any charred electronics and see how far it goes.

 

[funkuncut]

I got an immaculate iMac A1311 for 40 pounds - the HDD was broken, so I put both my drives into it and it works fine! Since everything else in my original one is in good condition, I think I'll take a punt on another logic board for 40 and try it with a spare HDD - if it works, I can give it to my children so they won't have to use mine to play games.....
I can't see anything scorched on the logic board, and, while I like to repair things rather than replace, trying to replace anything on a logic board (specially for 40 pounds) is way beyond my capabilities - I can replace components on a transistor or tube amplifier, but not things that I struggle even to see!
I'll get hold of another logic board and post results - many, many thanks for all help!

Paul

 

[lclev]

Good deal!

Lisa

 

[funkuncut]

I couldn't quite believe it myself! I was watching several ratty looking models just for parts when this one came up, and it was 1/2 mile from me - I made an offer and picked it up a couple of hours later. Another couple of hours and it was up and running. Probably used up all my luck now.......

 

[jasongoldworthy]

I couldn't quite believe it myself! I was watching several ratty looking models just for parts when this one came up, and it was 1/2 mile from me - I made an offer and picked it up a couple of hours later. Another couple of hours and it was up and running. Probably used up all my luck now.......

Well done that’s awesome news hopefully you can source another logic board and get the other one going