Apple has commenced a Power Mac G5 Repair Extension scheme for some Power Mac G5 systems that have suffered power supply problems.

Some new systems have suffered specific component failures within their power supplies. This is often experienced as a situation in which the Mac won't start up, but only applies to units within a certain field of serial numbers. There's no safety threat from the fault.

The affected Macs were: "Sold between approximately October 2005 and August 2006 and feature dual 2GHz, dual 2.3GHz or quad 2.5GHz PowerPC G5 processors," the company said.

If you have a Power Mac G5 that's suffering from this problem, then it may be eligible for free repair by Apple. The power supply will be covered by Apple for up to two years from the original date of purchase, the company said.

An extensive technical support document on Apple's website explains which serial numbers are affected and what users should do next to rectify the problem where it appears.