Restarted and No Video Output - Only 2 Diagnostic LEDs
This iMac is getting up there in age, but so far it’s been very reliable, if not very slow due to the original HDD. I bought an SSD, temp sensor and all the works and was going to upgrade the Drive soon, but then I was greeted with this lovely issue one day out of the blue. I powered my computer off perfectly normally the night before. Then the next day I went to turn it on, and I heard the HDD and fans starting up, heard the Boot Chime, but the internal screen wouldn’t even try to turn on, no backlight (and no image holding a bright flashlight up).
I found a copy of the Apple Technician’s Guide online and was going through the flowcharts there. I ended up at the “No Video” Symptom Flow. I tested an external display, nothing; then I tried with known good RAM and still no luck. So following the guide, next I cracked it open and checked the Diagnostic LEDs. Only 2 were lit up after powering on. So next I replaced the PRAM battery, and then re-seated the GPU (with new Thermal Paste), and made sure there wasn’t a speck of dust inside anymore.
Then I connected everything needed to test the Diagnostic LEDs, and still only the first 2 were lit up, 3 and 4 were dark…
I saw other posts on here where some people found one of the Inductors on the Logic Board (L9000) was burned out, but I checked mine and it looks good still; I carefully checked most of both the Logic Board and the GPU and all the components look good, nothing burned out.
So at this point I am at a loss as to what could be causing this no video problem. The next steps in the Apple guide are to replace the GPU and then Logic Board if the problem persists, but I don’t want to dive that deep on just a hunch. Hoping someone here can shed some light on this for me.
Many thanks and appreciation in advance!