fluid/ milky stain on tube in 60s blackface

[giovanni]

ok, so my bassist just picked up his bassman from being serviced, and i played guitar through it for about 10 minutes and it sounded awesome, then a fuse went.  so i put in new fuse and that one burned up after about 2 minutes.  then i noticed the power tube on the far end of the chassis was turning a milky, smokey color.  as far as i found out, he had the amp completely rewired to factory settings because when he received the head, the power tube in question had been bypassed, and somebody had done some serious mods to the preamp section. 

i told him to take it into the guy who rewired the head, any ideas?

also
http://cgi.ebay.com/1975-Sunn-tube-guitar-amplifier-vintage-6550-amp_W0QQitemZ260073309331QQihZ016QQcategoryZ10171QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[giovanni]

never mind, the culprit was a faulty power tube