Chosen Solution
iMac 24” – early 2008 - Mac 8,1 – model A1225 – EMC 2211 S/N: QP82805M0KM HDD – Hitachi Deskstar 1TB – Apple firmware 2007 Problem: Apple logo – chime – progress about 50% then reboots….. and again…. Procedure: Reset SMC & PRAM – no changeTested memory modules individually – no change.Safe-mode – freezesOptions – select Recovery disc – voice to select language (English) – then freezesUse USB with full version ‘Mountain Lion’ – boot freezesRecovery mode – reboot at 50%Single-user mode – boot freezesOption ‘D’ for hardware tests – boot freezes Used USB with ‘Mountain Lion’ installation files Get into Disk Utility and Terminal Use ‘fsck’ utility – “HDD is ok” …. “Volume has been modified” – repeated until all ok. Reboot – boot completed – graphics background appeared but no icons. Icons appeared after about 15 minutes. Repaired/verified permissions etc Machine working - OK Three days later –same problem. All boot options tried, plus booting to Internet for recovery – all as above Tried with USB - Full versions Mountain Lion/El Capitan – as above Tried with USB – Lion/El Capitan installation files – as above Single-user mode – ‘fsck’ – HDD is ok and “Volume has been modified” – repeat until error clears but it reappeared after every attempted boot. Tried all possible Boot options, also with various usb devices. Attempted Internet Recovery using cable-connection – no success. Firewire connection to MacBook Pro – Target mode - reformat iMac drive. iMac re-started - Attempt made to re-install the OS over the Internet – failure. Re-connect Firewire – Target mode – install El Capitan – reboot iMac – reboots at 50% Purchase and install Logic Board – eBay UK – ‘respected’ supplier, includes test report. Boot – then the video fails (!) – graphics for a few seconds, then black screen. Remove GPU card – remove & replace thermal compound – reboot – Graphics ok (should have done this while changing Logic Board !) Exactly the same as before – logo & chime then reboots itself at about 50% of the boot sequence. Tried booting from Lion & Capitan usb’s, and Lion & Capitan installation usb’s – rebooting at 50%. About the only thing left is the actual processor – but surely if it is a processor problem I wouldn’t get the boot logo or chime, or be able to use Target mode ? Any advice, suggestions, or information greatly appreciated – this is driving me mental ! Note: I’m a retired electronics and IT engineer – many years repairing PCs, just over 2 years repairing Macs - have repaired 54 Macs, including 12 old iMacs ….. I hate to be beaten – but maybe this one…? Thanks in advance - Peter
I suspect you have a hard drive issue here. If this is a replacement drive did you make sure the drive was spec’ed correctly? Keep in mind this is a SATA II (3.0 Gb/s) system so you need to get another fixed SATA II drive or an Auto Sense drive that will adjust to SATA II. Most drives today are only fixed SATA III (6.0 Gb/s). As an example this is an auto sense drive Seagate FireCuda note the SATA interface line lists SATA II (3.0 Gb/s). If the spec sheet doesn’t list it its not likely to work reliably. As an example this WD drive is a fixed SATA III (6.0 Gb/s) speed WD Black Series and you will have problems getting to work reliably in your system.
