Bought a NOS 6as7g froma local shop; it makes a loud popping noise in the first 20 minutes or so but seems to be working fine otherwise. I don't have a tester, but does this mean I got a dud?
amp is a wa2; one of the 6as7g tubes came to me broken so I bought another unmatched nos rca tube (above). Also have one 5998 tube that's good and another with broken glass in it

I'm off to a bad start lol, should I just sell the onesies I've got and start over?