Having said that I wouldn't post again, I have been left a few PM's which go a long way to explain why I received such a warm welcome here.
I did not intend to insult anyone, or slag off the PRS brand. Indeed I have just placed an order for a John Mayer signature model which I think shows my loyalty to the brand.
The problems I had with the Zach Myers guitar have only this morning been resolved.
I replaced the faulty potentiometer with a new one, and did some rewiring, the standard of the wiring is not really very good. That solved the back ground crackle on the neck pick up.
The most frustrating problem was the lack of sustain particularly on the 3rd string. Open wasn't too bad, but fretted anywhere the string just didn't ring like the others. I modified the pick up mounts to stop the pickups from resonating, and the same with the truss rod cover, in case the annoying vibration from these was cancelling out the string vibration, but it made little difference. I then found that the stop tail bridge was rotating forward under string tension, and that the 3rd saddle was machined at a slightly different angle to the rest, meaning that the string was free to vibrate along the line of the saddle rather than at the end. It sounded like a Sitar, the saddles on which are designed like this.
see link;
http://www.sitarfactory.be/maintenance/jawari/
Once I had identified this problem I re-profiled the saddle and cut a new groove, and shimmed the bridge to prevent the forward rotation.
The short scale length which is unique to this signature model guitar adds to this problem if the saddles are slightly out on the profile, or the bridge rotates forward more than an acceptable amount. Being a lower string tension, it exaggerates these problems. With a higher tension string the saddle profile would not be such a problem as the string would hold itself in place more readily. Which is probably why so many Zach Myers guitars are appearing for sale second hand. Indeed if my final efforts to fix it hadn't been successful, I would now be trading it for something else.
I now have a guitar that plays and sounds as good as it looks.
I wonder how many of the owners of the Zach Myers guitars that are up for sale, as mentioned in the previous post, are now put off from ever owning another PRS, if they experienced the same problems I did, but were unable to fix them??