Any way to revive Mid 2007 24" iMac struck by power surge?

I was given a 24" iMac from 2007 for free, reason being the computer had been killed in a power surge. The previous owners had already gotten a new iMac, so I can keep this one. However, I would like to get this one back in working order, despite being 10 years old. From some other guides I have looked at and inspecting the computer, I tried a few things.

• Reset the SMC (didn't work)
• Reset the PRAM (also didn't work)
• Check the diagnostic LEDs (I only got 3 out of 4)
• Insert some memory (because the memory was removed when I got it)

If I don't get the fourth LED:

• LED 1, for the trickle voltage from the PSU being detected by the main logic board, illuminates.
• LED 2, for the main logic board detecting proper power from the PSU, illuminates.
• LED 3, for the video card (in my case, Radeon HD 2900 Pro) communicating with the computer, illuminates.
• LED 4, for the computer and LCD display panel, unlike the others, does not illuminate.

Source: iMac Intel 24" EMC 2134 and 2211 Diagnostic LED's

Because LED 4 does not illuminate, I get the SuperDrive initializing, fan powering and spinning, and hard drive power on, but no chime or display. I do not know what is causing my display to not communicate with the logic board, as I have reseated the connectors a few times and got the same results. Because I do not have a Mini DVI adapter to hook up the iMac to an external display, I do not know if it will give me a different result if I hooked up an external display. Also, when I shut off the computer, and then attempt to power it on again while still plugged in a few minutes later, no LEDs appear, and I have to unplug and plug the cord back in to get a response. Long question short, what do you think is causing the fourth LED to not illuminate and give me the no display-no chime problem?