How to tell vacuum tube is gone bad??


I recently purchased primaluna prologue 3 and I connect with dynaudio bm6a.

First I saw is lights of three vacuum tubes are dim and

other lights of three vacuum tubes are bright.

Among 6, 1 of vacuum tube has little soot on wall.

When I connect output-2 with bm6a speaker (active speaker), the volume is very low even I tune max volume.

When I connect output-1 with the speaker, the volume is loud enough with 1/3 of preamp volume.

Are these symptom indicated bad vacuum tubes?

Any other way to check vacuum tube??
chunkichunky

Showing 1 response by zd542

"How to tell vacuum tube is gone bad??"

Try the tubes in a friends amp. If nothing bad happens its probably safe to put them in your amp.