64 Bandmaster Whining Sound

[dumbassbob]

My Bandmaster was sounding great,then I warmed it up it started making this whining sound on normal channel it also lost some volume and the tone was harsh,If I go in to look around what should I be looking for and howdo I test to see if something is burnt

[soundguruman]

I think you have a bad pre amp tube or the bias has failed. Are the power tubes turning red?

[dumbassbob]

The tubes were a bit hot but not glowing red... NOS RCA Then I changed the tube back to the JJ's Now when I turn the volume knob the whing changed pitch a little ,But the Vibro channel do not do it ,but it has lost some volume too and sounds a little harsh I was hoping it was a resistor drifting or burned

[soundguruman]

You need to change preamp tubes before measuring the resistors. Don't you have a good new tube to test with?
change them one at a time...and test if the noise is gone each time. you can find the bad one that way for sure.
I would not assume the problem is inside until the tubes have been swapped out, at least one at a time.

[dumbassbob]

I changed only the first 2 preamp tubes and the PI,I didn't think the New tubes in V-3 was bad but I will check it again...I still think I poped some thing inside Its a great sounding amp,but OLD