Ok, so on quite a few occasions over the last couple of weeks when I connected and powered up my JTV59 I realised one string (the b )
was not picking up the sound while all others were ok.
I found that after rapidly plucking that b string eventually it would pick up ok.
Naturally I thought bad piezo, but being suspicious and curious (I have electronics skills) I decided to open up the the cover plates on the back and poke around (not literally, and with the guitar off) . Nothing obvious could be seen, so I made sure all the connectors were seated properly and popped the covers back on.
So, fired up the JTV again and to my surprise the b string was ok BUT the g string had the fault. So putting 2 and 2 together concluded the piezos probably fine but a connector was the culprit.
Covers off again, and fired up the JTV and EXTREMELY carefully moved the wires on the connectors with a wooden toothpick whilst plucking all strings one at a time.
RESULT : fault on one small connector which has 7 wires if I recall that obviously are piezo related.
Made sure all 7 were seated in that connector and so far all is well.
Now those with common sense and no electronics skills would probably send it back as faulty for a replacement but, as I'd set the guitar up exactly as I wanted including recutting the nut which was shamefully high, I wanted to troubleshoot the problem myself.
If any of you have a similar problem I would be happy to post a pic of the offending connector if you wish to look for yourself.
Can't believe I have voided the warranty as there is no sign of me touching anything!