Ron,

On your 568, might want to try removing the ferrite beads and installing two Auricaps .47UF at least 600V (could also get 1500V). If it were me I would also add a 3rd Auricap .1UF 1500V. The caps are placed across line & neutral right at the IEC. This is the famous Auricap tweak. Red lead to line & black lead to neutral. I have used it manytimes on various components and always loved the result.

Could also install two large Bybee's (large size Bybee) (in addition to the Auricaps), one on the line leg and one on the neutral leg, just behind the IEC.

You can get the Auricaps quickly & easily from Sonic Craft. http://www.soniccraft.com/auricap.htm

The Bybees you can get from Parts Connexion: http://www.partsconnexion.com/catalog/accessories.html

Finally, If you have some ERS cloth (if not can get it from Parts Connexion on Bybee page - see ERS tab) I like to install some smaller size pieces around the power supply. Installs easily with hot glue.

All of the above is also in my G68. I have no affiliation with the above companies - just a happy customer.

Will be interesting to see what power Supply is in your 598.