I recently replaced the psu in a friends Sony Vaio desktop because it failed testing. At a very high cost he purchased a replacement from Sony. When it arrived I tested (using both 20 pin and 24 pin testers) the replacement unit to find the -5v circuit was not lit up. In standard psu's this usually indicates failure in itself. I contacted Sony and received another psu. This one has the same indication, the -5v is not lit. Now I could understand the possibility of one of the testers being bad, but I get the same reading on both. Has Sony disabled the need for this circuit on their systems? Do I continually get bad products from Sony? Please help.