Haven't tried zapping it yet, since at least it has a picture. I was REALLY tempted to shoot it, but when I put the 470 in the CLEAN-BALANCE mode, the faulty filament went like a 60-watt lamp. I agree it's probably debris in the tube, or possibly an open connetor in there causing the filaments to run in series this way? That would explain one bright one and the others low.
Thanks for the tip on the RCAs having the upside down gun too
Charles