dismantled my #amiga #a500plus to find out that the clock battery has leaked and caused some corrosion near the Gary chip, very similar to https://hackaday.com/2019/01/25/resurrecting-an-amiga-500/
I don't have the tools to repair it, unfortunately :(
I managed to remove the battery with a screwdriver (corrosion made it easy to snap the metal at the base), and cleaned the corrosion a bit with vinegar as recommended it the comments on the hackaday article upthread.
First boot worked to some extent, got the kickstart insert disk prompt, and booting from a floppy almost worked (the internal drive on that machine is faulty). I connected an external drive, but restarting afterwards just gave a blank black screen.
A500 troubleshooter on the internet archive suggests it might be the power supply (works in another A500, so not that), 68000 CPU (suggests to check for overheating), Fat Agnus chip, or the X1 clock crystal. I suspect it might be something heat related, because it worked briefly after being off for some time. Will test again tonight.
It booted to the purple-background insert disk animation! Joy.
But then I got over-excited and plugged in the GVP HD8+ external hard drive and RAM expansion, back to the red bad ROM screen upthread. Then after unplugging it again the A500+ is now back to blank black screen (not no signal), no drive clicks. Back to where I was April 22nd.
So I guess the expansion is faulty in some way that (hopefully temporarily) messes up the state of the A500+ and makes it broke. Won't be plugging it in again any time soon.
Wow, poor amiga!
What a machina!!