HOW TO FIX iMac 27" missing ferrite bead L5500 / fan speed issue?
I’m new here, and I have a question for the experts of the forum. I have an iMac 27” Mid 2011 (A1312 / 3.4 GHz - 8GB RAM) that I purchased online months ago from a person that lied about its conditions: the hard drive is failing, and the graphic card died on me about one month ago.
I replaced the graphic card with a new one, and when I put everything back and turned the iMac on everything was working again, except for the CPU fan that started spinning like crazy. I downloaded and installed Macs Fan Control, and according to the app the values are the following: ODD 3800 - HDD 1100 - CPU 4200. As you can see, the only temperature sensor that is working properly is the hard drive one. At the moment I don’t care about the optical drive since I never touched it and it’s still working regularly.
Despite being extremely careful and using appropriate tools, believing that I have damaged the thin cables on the CPU heatsink and fan I replaced both (for just $6 each), but the problem persists. Thankfully, during the repair process I took many photos and videos. Comparing the before and after photos I noticed that I lost the ferrite bead L5500 close to the AMBIENT TEMPERATURE connector, and a very small portion of the motherboard trace connected to it came off, too (L5501 is still in its place). Not sure how that happened since, as I said, I am extremely careful and never use screwdrivers to remove cables, plus this is not the first time I open computers and unplug thin cables for repair. After reading that many other users lost ferrite beads in the same area and are now experiencing the same issue with the fans, after inspecting my motherboard for other possibles damages and/or missing components and not finding any it’s my understanding that this is really some kind of factory defect as other people complained about.
I grew up watching both my granddad and my dad repairing electronic stuff, but unluckily I don’t have exceptional soldering skills. While I can always learn how to solder things, unluckily I cannot read schematics, don’t know how to use a multimeter, and know nothing about ohms, volts, etc, but I am a resilient person and I am positive that I can fix this iMac by myself the same way I fixed other things in the past to save money. My dad lives in a different Country and I live in the US, so shipping the motherboard to him is out of question. After spending almost $200 for a new graphic card, CPU fan, heatsink, and thinking how much more I will have to spend for SSD, 2.5” to 3.5” mounting bracket and OWC In-Line Digital Thermal Sensor, I really need a quick, easy and cheap solution.
I keep on reading online that it is possible to fix this kind of damage by either replacing the ferrite bead with a single trace of solder that covers its pads on the motherboard, or by bypassing the damaged area with a “bridge” made with a small electric wire. I think the latter could be the best option in my case since it looks like one of the two pads and part of the trace got ripped. I’m just not sure where to start, so I really need some help. The explanation should be very elementary. Images/drawings will help a lot, too!
Here’s the photo of the damaged area of my motherboard (the red line you see is the copper trace that came off):
I know I am not the only one experiencing this problem, so your replies will be extremely useful for many other iMac users, too.
I’m adding two additional photos that I took a couple of minutes ago, one with a regular flashlight and the other one with the UV light on to highlight the damage underneath and around the missing L5500 ferrite bead. Hope this helps….thank you!