Machine powers on, fans spin, no chime or video
Recently picked up this iMac and tried to power it up; it turns on, the fans start spinning, and the sleep LED comes on, but the iMac doesn't progress past this state. I've tried resetting the SMC and PRAM, but no luck. Removing the bezel, I can see the first three diagnostic LEDs are lit when the machine is powered on.
The system doesn't appear to be supplying power to USB peripherals, as I plugged in a keyboard/mouse and got no lights.
The service manual for this machine lists these symptoms and recommends replacing the RAM (tried that, no change) before concluding it must need a logic board. I wouldn't think it economically viable to try and source a logic board for a machine like this, but I figured it'd be worth asking if there are any other things I should try before giving up. I am aware this model iMac is somewhat notorious for GPU issues, but I imagine I would run into the same problem as with a logic board when it came to replacement.
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Are you getting any reaction on the display? Do you see a shift in the grey screen when powered? Using a flashlight pressed onto the display at a sharp angle do you see the faint image of your desktop and its icons?
The fact the USB ports aren’t offering up power is a bit concerning, that aims me to the power supply or a problem within the logic board.
@danj No change in the display as far as I can tell. Using a flashlight didn't reveal anything, unfortunately.