Hi,
Have you tried removing and re-inserting the CPU, Kickstart and other socketed chips?
Are you using the original A500 PSU?
I have uploaded a diagnostic disk with repoair utilities on my website at
www.ianstedman.co.uk/PU288.DMSIf you uncompress this disk, you can either boot from it or if you are in workbench, run the program 'S17' from the root directory. This is the original C= A500/A2000 diagnostics program.
Good luck,
Ian