it's now dead.it spontaneously reset, then crashed after boot with a software failure message (red box flashing on back background with hex codes in side), clicking the mouse button to reboot then popped up the screen attached, and now (even after unplugging everything including the internal RAM expansion) on power on it just displays a black screen (signal is present) and the power light, but nothing happening, no "insert disk" screen, no clicking drive, nothing
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.
This morning the A500+ boots fine, from floppy disk in the external drive.