I discovered this today. Useful information for any Quad valve amp. owners - recovered web pages that used to be on the Geocities server. I've still got these web pages on my home P.C. Here's the link:-
http://www.geocities.ws/ResearchTriangle/Lab/6722/Unfortunately the links in the 'Links' section are dead including the one 'Quad II mod pages' I mentioned in a post several years ago.