Has your set ever arced? Sony had a bulletin for sets that had CRT base arcing, as sometimes the arcing would trigger a shutdown.
I'd post it here, but the fourm limits the size of PDF files. Essentially, you remove the CRT socket, remove (very carefully) the index key cap on the base of the CRT, and then remove the RTV at the base of the CRT. The RTV they used didn't have a high enough dielectric strength when cured to avoid a flashover. They specify a Sony-part numbered RTV, but RTV3145 will also work.
Good news - the bulletin is here:
http://ebaman.com/index.php/componen...e,25/?Itemid=0
TVP0557.pdf