a2115 not power

[Joyoungjae]

Hello everyone
It's late at night here.

I have a repair a2115 model that came to me.

The symptom is that the power is not turned on and only check LED 1 is on.

It's the same even if you change the power board, and it's the same even if you short the on/off terminal of the power board with tweezers to check if the power button is defective.

It was difficult to find a board view of this model, so I took a picture to see if there was a short circuit, but I couldn't see the short circuit. Is there another way?

I hope everyone has a good day today!!

[mon2]

Remove all power. meter in resistance mode. Measure the resistance to ground at each coil on the board. Hunting for any low resistance reading. I recall a similar case on a 5k iMAC which another shop gave up on and we found a shorted cap on the 5v USB rail that was causing the same LED power on fault. The shorted cap was a polarized tantalum that was located with voltage injection. Do not proceed till we can agree on the fault but do measure the resistance to ground without power to the board.

[reformatt]

I haven't had anything beyond 2017 to work on but most issues with motherboards in iMacs are shorted 0201 caps. On 27" models they are usually on the board side facing the screen, at or just below where the screen sits flush at the bottom due to dust contamination or corrosion. IIRC, 2nd LED is for all sys pwrgd. Usual way I troubleshoot on the bench is apply 12V via power supply to the main power connector, and check which rails come up.

EMC number or board number is really needed to help further.