WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Can anybody tell me what has happened to this valve. I bought seven on ebay and one looks faulty. They should be unused and the rest look good inside. They are for a driver for an amp and I only need four of them.
That tube seems plain new, it isnt even a quality issue some tubes had its outer plate/screen covered in getter material that its heated in the production chain if its totally black or brown near the filaments, then its likely an used tube, yours seem one of those called a NOS tube.