A2115 27" 5K iMac not turning on after SSD upgrade.

[joshAU]

Hello again.
I just cloned a customer's iMac internal hard disk onto a 2.5" SSD connected via a USBC adapter.
That completed successfully.
I then removed the AC power, removed the two connectors for the screen, took out the screen, and then replaced the hard disk.
Prior to reassembling it, I tested it - but it appeared dead.

I get no picture, fan or sign of life.
I only get 1x green LED, the second from the left of the 5x LEDs on the logic board, which I presume means the power supply is OK.
I tried to connect with a Mac using Apple Configurator, but it doesn't detect it at all.
I've disconnected the new SSD.

I've reseated the RAM, and tried with individual sticks, and even tried with no RAM, hoping to perhaps hear an error beep, but nothing.

I don't understand it - I had all power disconnected when I removed the two connectors to the screen, and when I disconnected the hard disk and connected the SSD and reassembled it.


Any help greatly appreciated.

 

[2informaticos]

What is 820-xxxx code of your board?

 

[joshAU]

Hi 2informaticos.
Sorry for the delay, I have been away from work for a few days.
I stupidly reinstalled the mainboard, without getting the model off it first.
However, checking the serial it is a 2019" A2115 iMac 27", which, according to the follow site, indicates that it must be a 820-01236 logic board.

Board Number by A Number - LogiWiki

We have Apple MacBook and iPhone Diode readings and general fault finding information compiled by the leaders in this area

logi.wiki

I replaced the BIOS battery, which was only at about 2.5 volts, while I had the board out.

The only LED lit is LE0301 - "Its plugged in".
No other LEDs light up.
I've bypassed the power button, but still no other LEDs, no fans or chimes.
Thanks again.

 

[2informaticos]

Then is not a T2 machine.
No reason to use Apple Configurator in this case.

You should remove the board and test it on the desk.
12V/5A lab power supply is good enough to power it.
Board must turn on automatically if CMOS battery is removed.
However, I recommend to use a switch attached with 5-10cm wires PWR_BTN_R.
It helps you to check the board reaction.