If you're not sure what's wrong with it, what makes you suspect a tube? (Not that you're wrong, but tubes issues will not generally stop the PJ from firing up to the point of throwing some type of diagnostic code).
"broken" is not enough info...does it just fail to power up or what are the symptoms of it being broken? How do you know you need to change a tube?
when i got it the red led- hold down EHT was on, found out Red tube is broken in half, took some advice from guys on curtpalme.com and disconnected it and powered up and both green/blue are now working.
I guess i have to find a redtube first before i can change it.