Hi pekmez! I've got a non-working A4000 tower too
Only person that fixes Amiga's in the US anymore is Ed Jeffries', Video Lab. You caould just do a search here, or on amiganews.de for his phone #, etc... But, be aware, according to Ed, he is running out of working chips, etc. Assuming it is a hardware prob. , of course.
Maybe post as much info as you have about your A4KT, and heck, your A1200 too, while you're at it
