Why does the driver tube glow so RED

[sydney]

Why does the tube glow so bright. Is the tube bad or some other component. Driver tube NoS Tungsol 5687

 

[Dev.R]

Probably a Red Plate. The tube may be drawing excessive current . The Tube should be a faulty one.
Had a similar issue with my 6550 . In the end replaced the tube and back to normal.

 

[sydney]

Yes replacing the tube solved the issue