If your scrapping it anyway whats to loose?

I'd try to save it. If you can't though keep the HDD, optical drive, and RAM as those are industry standard as far as I know and could be re used for other builds.

It all depends: how badly do you want to have a G4, and how easy is it to get a G4 in Canary Islands, Spain?

Carlos S. M. wrote:

Sadly, Power Mac G4 PSUs are too expensive and none ships to my region,

Have you tried Ebay for a power supply? Last time I checked Macs and their parts were quite easy to find...

but i found this guide if i have to mod an ATX extension cable to use an ATX PSU on the G4 if i have too, i still have the old dead PSU
http://atxg4.com/quicksilver.html

Should i try that or scrap the Mac?

You can try that, or pop open the original power supply and check whether the capacitors are okay (I bet they're burst). If you're good at soldering you could try fixing the original PSU.

You could just convert a bog standard atx psu for little or nothing but Macs are generally worth saving knowing that someday they eventually start going up in value. There is still a lot of software that only runs on these older PPC macs.

I have used in the past a modified ATX PS for a Powermac; not a Quicksilver, but a Sawtooth. It worked like a charm. In fact it still does.

I'd mod an extension cable, this way you can still use the PS as ATX if you want to. And yes, you should try to save it if you can.