iMac mid2010 bypass SMC, fan running, no chime?

[tanventure]

Hi,

Picked an iMac mid2010 21.5 inch recently, it won't turn on.

I have done the followings:
1. checking PSU, seems working ok, pin 4 voltage 12 v.
2. checking Power on button, it works.
3. LED1 on the logic board is on once iMac is connected to power.
4. reset PRAM, SMC, nothing changed.
4. By bapass SMC iMac can be turned on, fan running fast, but no startup CHIME! Bypass SMC was done by following this link. But LED2 still off, black screen.
4. Checked RAM chips, and switched to another RAM set, nothing changed.

I have read the Apple user manual for iMac at http://tim.id.au/laptops/apple/imac/imac_21_mid10.pdf, could not figured out what to check next, is the logic board bad?

I have not checked the on board battery yet because it's rather hard to remove it from iMac, wonder if there is any way to check battery voltage without removing it from the logic board?

Appreciate suggestions/comments as to what to check to make my iMac start up, thanks in advance for sharing!

 

[McTinker]

What does it do? It start up but no image? Do you have another mac so you can try to start it up in target disk mode?
I've has a mcbook pro 2011 who looked dead. The extra gpu was dead. Several flashes of the pram/vram, and starting from internet recovery worked for this macbook.

 

[tanventure]

Hi, McTinker,

Thanks for sharing your success in fixing macbook pro, I am looking forward exploring ways to fix my iMac.

I can't turn on my iMac unless I bypassed SMC, if I bypassing SMC I can turn on the iMac, Fan running loudly, black screen; The iMac uses a SSD, so I can't hear any noise of SSD, no noise from DVD driver as well.

Yes, I do have another mac, in fact I was thinking to put my imac in target mode, but not so sure how to do it because I can only managed to turn it on with bypassing SMC.