iMac don't start...second LED lights up intermittently every 3 seconds

Hello

One year ago (more or less), when reassembly CPU on socket (after replace Thermal Past/Thermal Pads), bent 2 pins on socket (but correct this issue), also "split" Fusion Drive (replaced the Apple "Blade" with a OWC 480Gb and SSD SATA Crucial MX500 2TB), upgraded RAM from 8 GB to 32 GB, replaced PRAM battery(BR2032)... and works great for a year...

Some days ago iMac won't start...I changed the power supply because it didn't start...but don't solved the issue...

Could this be related to the issue of socket bent pins ? (a year ago)

@boxerboss - Sadly yes 😡 the bent pins are weaker and over time fail. You could try reseating the SO-DIMMs. Do you have an external bootable drive to double check if the current boot drive is messed up. But I’m leaning the socket is the issue.

Hello

I already removed RAM and put it back in...issue persists

Do you mean to try with a USB bootable Big Sur?(the macOs installed)...and try to start in Recovery Mode?...or Safe Mode ?

@boxerboss - I just find having a bootable external drive is quicker to just boot up from. You can also try booting up under anyone of the Startup options, do any respond?

Can I create a "bootable external drive" for my iMac in other Mac?