Should I continue to put money in this amp?

[GoldenVulture]

I thought that too, but the bias will hold at the 18ma recommend by Lee Jackson. The tubes just started changing color last night. I just want to believe it's tubes. I've seen the same thing before.

At what point did you measure the bias ?

Is there  a model name/number  other than " Crate Stealth 50w head " ?

I was trying to find a schematic for it but couldn't find anything with Stealth in the name. I did find a big repository of crate stuff.