Imac 820-00597 not reading HDD correctly

[ielectron]

I have on bench now iMac with have a weird HDD issue , it is showing unmounted HDD once I trying to format it will show the error. I get HDD working for a 10-15 min after replacement and issue come back. The machine come here with this problem not recognising HDD with was looking like dead HDD.
Replaced HDD twice for brand new
replaced hdd data cable
replaced the 4 caps C3821, C3822,c3823,c3824 suspecting issue there same issue persist
I've measure the other connector J3830
PP5V_S0_HDD -- 5V present
SMC_OOB1_R2D_R_L -- 3.3V
HDD_OOB1_D2R_L -- 0.013v jumping to 0.023V

Thanks for help

 

[2informaticos]

Possibly PCH internal failure...

 

[ielectron]

Hi Thanks for response,I replaced PCH just now to see as I have a new ones in stock, machine shows up HDD correctly and after reboot was same issue.
I checked connection between PCH and SATA connector , they are okay. Also after fitting PCH there is a resistance on all 4 caps from PCH side.
Any more ideas ?
I am thinking about reball SMC.
It looks like loose connection after warming up board it started working? What do you think about SMC reball?
Do you think this value is correct ? HDD_OOB1_D2R_L -- 0.013v jumping to 0.023V

 

[2informaticos]

You should compare the readings between working and non-working state.

SMC shouldn't be involved, but you can try reballing it.
Check if is possible to locate an PCB area reaction to heat.