Chosen Solution
During the installation of High Sierra, after a restart my iMac now gives a SOS signal at startup. 9 Beeps (3 short, 3 longer, 3 short) I tried the reset of NVRAM and PRAM and other relative keyboard combinations at startup without result. I tried all 4 RAM modules one by one. Do I need to replace a battery? Do I need to restore firmware? I hope that someone can help me Kind regards, Kris
Sadly your systems firmware is corrupted! You’ll need to create a restoration CD following this Apple T/N: About the Firmware Restoration CD (Intel-based Macs). Update (09/29/2017) Sorry Kristian I aimed you to a dead end ;-{ I forgot the 2010 model is one that Apple doesn’t have a Firmware restore CD available. Give Apple a call or visit an Apple Store to see what they say. Explain you were doing an OS upgrade from ??? to High Sierra. Update (10/06/2017) Your system has a BIOS (EFI) which has firmware on it. During the OS update it is often updated as well. During that process it likely got corrupted. The reason your system is beeping is the check sum of the firmware is wrong. Its designed to do this when its bad. If Apple won’t help you you’ll need to either replace the logic board or find someone who can replace the BIOS chip on the logic board. Here is the location of the chip on the logic board:
. Here’s one source for the chip. You’ll need to give them your systems S/N which should be on the bottom of the foot: BIOS EFI firmware chip: A1312 Apple iMac 27" Logic board: 820-2828-A
