The tube is connected to the preamp board by a ribbon cable. There is a good chance the ribbon cable connectors need cleaning.
Of course, the tube itself could be dead, but cleaning the connectors costs only a few cents' worth of contact cleaner, so it's worth trying first.
More GAS than talent or patience.
Crappy Bassist with Expensive Gear Club #19 • Official fEARful Club #62 (15/6/1 + 15sub)