A500 woes - again

[linuxlove]

This time, it's actually an issue and not a floppy disk I forgot to remove

So I finally got around to getting replacement filter caps for my A500 and I snipped off the old ones and was soldering new ones in place when I noticed something: R302 was burned. I found a replacement in my parts box, soldered it in and hit the on switch. And it booted! Except there was one problem: Smoke was coming from the motherboard and I think the computer also locked up. Taking everything off and yep, R302 was burned. What's more, the computer no longer boots. The keyboard light goes from a dim red to a slightly brighter red but there's no floppy drive activity and nothing is shown in the screen.

Given that I'm only armed with a soldering iron and an inexpensive multimeter, where should I start looking for the trouble? Or should I call this A500 toast?

 

[SParent]

Looking at A500 schematics, and assuming I have the right version, R302 is in the power circuitry of the LF147 Op amp used in the audio filters. I would start by checking the other resistor R301 and four capacitors C301 to C304 of this circuit. If they all check out OK, I would then replace the LF 147. I wouldn't call it toast, as the computer boots and works, at least for some time, before burning R302.