Heater resistor burnout

[Oddvar]

Hi.  Does anyone know what causes a heater resistor to burn?  It seems to be a 470R 3.75w Dale Vishay in this Mesa Boogie Mark IV.

And could I change it with a 470R 5w resistor?

[shooter]

excess current more than likely burnt it
I only have the MKII schemo, it shows 100ohmers like most builds if that helps

[Oddvar]

Here is a pic, clearly burnt...

[sluckey]

That's not a heater resistor. It's a screen grid resistor. Excessive screen current burned it up. Most likely a bad tube.

[Oddvar]

excess current more than likely burnt it
I only have the MKII schemo, it shows 100ohmers like most builds if that helps

It is 470R, 3.75w for some reason.  I was wondering if wattage could go up to five.  And if it could/would be the power tube that caused the failure?

[PRR]

...if it could/would be the power tube that caused the failure?

Most likely a bad tube.

[Oddvar]

That's not a heater resistor. It's a screen grid resistor. Excessive screen current burned it up. Most likely a bad tube.

You're right, I thought it was number 7, blame it on the bad eyesight...