Mac 512Ke Bright horizontal line on screen

[Sayonara!]

I have a Mac 512k that when powers on, makes a corrupted beep and displays a very bright horizontal line on screen. I've tried tapping the case and nothing happens. I've reflowed solder joints and nothing happens, and I've checked the voltages and they're all okay, what should I do?

 

[m1maverick]

The first thing I always suggest is to inspect / replace the capacitors. Electronics of this age are prone to have failing / leaking capacitors so it's my number one go to check unless I have reason to suspect otherwise.