21" imac late 2013 repair question

[getgo100]

Hi all,

I have a late 2013 21" imac. There was a short circuit at home after which the imac did not boot up at all. Checked the power cord fuse tried to reboot several times but nothing. Took it to Apple who said either the Power supply or the logic board is gone and they could only determine that after opening it up. Way to expensive for me.

I don't know much about computer hardware but managed to open up the imac and remove both the power supply and the logic board. Is there any way to test which one/s is/are spoilt? What would I need to do to test them?

Many thanks,
Gunter
London

 

[MBAmtloin]

BE CAREFUL
since the imcas open, my imac G4 powered on with out the logic board attached, they ran a black screen, and a constant chime.
if that is the case, the logic board suffered a short,
look for anything burnt or weird on the logic board first before attempting anything electrical.

good LucK and sorry this happened.

 

[getgo100]

BE CAREFUL
since the imcas open, my imac G4 powered on with out the logic board attached, they ran a black screen, and a constant chime.
if that is the case, the logic board suffered a short,
look for anything burnt or weird on the logic board first before attempting anything electrical.

good LucK and sorry this happened.

@MBAmtloin;1839649 - thank you for your reply. Actually, visually nothing on both the power supply or logic board seems off at all.
Is there any way to test them individually?

 

[Raz0rEdge]

Honestly, to be able to diagnose power issues, you need to know somethings about electronics. You'll need a good multimeter and have the schematics (you will not get this) for the circuit you are trying to check. I imagine the power supply is the cheaper of the two parts, so find one on ebay or something and try it out to see if things work. If they don't, then you'll need find a cheap logicboard that matches your machine to try out.

Make sure that you are using a surge protector in your house for all electronics. It's cheaper to replace those than iMacs.

 

[getgo100]

@Raz0rEdge - thank you for your reply. It looks like this is beyond my capability. Thanks for the clearing that up for me and for the advice

 

[MBAmtloin]

getgo100: removing the imac screen is a well worthy of being capable of climbing the computer repair mountain.
the screen removal is not for novices, so good for you,
but all this hip-hip hooray aint fixing your imac.

i would put everything back and see what happens.

the powerbook, ipod, imacg4 and now my macbook air all needed repair and worked after tear down.
my macbook air would not type for 17 months until i finally got the ribbon set perfectly in the trackpad latch just last friday.

 

[getgo100]

@MBAmtloin - Thank you for your reply. You know, I think that's actually a good idea.. I think that's exactly what I'll do

 

[Vogelek23]

First of all, you need to re-assemble the machine (do not fit nor connect the screen yet). Then connect it to the power outlet (PLEASE BE VERY CAREFUL BECAUSE THERE IS A LIVE MAINS ON PSU!) and watch a diagnostic LEDs status (see attached picture). First LED is a Standby LED (means it should lit up as soon as the computer is connected to the mains). Second LED is AllPowerGood LED (means when all SMPSes fire up, this LED lits up). 3rd LED is a GPU LED (means when graphics chip is powered and initialised, this LED lits up). And the last one is Screen power LED (means when screen is properly detected and powered, this LED lits up).



If the first LED does not lit up, it is most likely dead PSU. If the first LED lits up but there is no signs of life when you try to switch it on, most likely it is bad SMC. If the machine turns on but switches off immediately, there is a short circuit on some low-side power rails etc. Please share your diagnostic LEDs readings.

 

[chscag]

Welcome to our forums.

Good stuff, thanks for sharing that knowledge.