iMac A2116 820-01237 Chime Loops

Hello again after a while. As I am not doing repairs now, but I have my own iMac. I am having a problem with it.

A week ago, I have dissambled my iMac, to check if I have nvme slot and my processor is soldered or not. Then I have decided to renew my thermal paste also. I have done everything good (thats what I thought but when re assemble the imac and press the start button, then I heard the normal chime and see the apple logo but then another chime but quieter than normal but in the loop. Sometimes it loads the system but not everytime. And sometimes internet recovery loads but sometimes not. I dont know what is the problem. First I thought the processor not placed very well so checked it several times. So yet, I dont know where to start to check. I have inspected the mainboard but couldnt see anything also. Only think left in my hand is the cable for hdd. And I know that there is no boardview for this mainboard also. Could you please help with this?

820-0597 schematic may help you.
Check if you reconnected properly all the cables.

Do you have fusion drive installed?
Can you run embedded diagnostic test?

hey thank you for the schematic offer. I have Crucial SSD installed. But tried fusion drive also. I have checked the cables but I am a bit suspicious with the highlighted cable on the attached photo but not for sure with that also and I dont know what this cable for?.

I have checked all the cables one more time and had a chance to do diagnostics test but test said everything is okay.

And not sure but when the computer waits for a while powered of and then I start it stucks on apple logo and chime, then I do smc reset then it starts normally but still not everytime.

As I have renewed the thermal paste of the cpu could it be cpu? But sometimes it is running normally without any problem sometimes not. Really not sure what else should I look for.

Just in case, check the CMOS coin cell.

Okay I have checked the CMOS coin cell. I will get the new one tomorrow but as you can see on the attachment the coin cell is on the mainboard is BR1632A but when I search on internet I have seen only BR2032 coin cell should be placed. Can you please also inform me which one is true?

2032 size is normal I think.
Just be sure it fits perfect there.
BTW, did you check the voltage of actual cell (onboard)?

Unfortunately my ampmeter broken down and it is cheaper to get coin cell now then ampmeter and quicker

I will try to get it today and let you know the result later today.

But if I can find a meter I will get one so do you have to measure the coin voltage on borad when the device turned on means on chime loops right?

NO!
Check coin cell voltage onboard, without power connected.

I have checked the voltage of actual cell coin and it is 3.04V I found 2032 also at home but I think that does not fit here. So where else should I look?

I have realised that one of the pins of the cpu ( 734. pin on 820-005597 boardview where cpu seats) bended but when I am trying to correct it it totally broken now. I dont know if this cause a big problem I have thought maybe the thermal paste blocks the heatsink to give the right pressure from all sides to cpu but it still same. Chime looping. Here is an video also. ( https://streamable.com/wikt22 )

Check the behavior in safe mode and SMC bypass.
Test disconnecting audio connector board.