vho ballast

[mm16]

Im having touble with my retrofit 4 t12 powered by a vho ballast. It will only stay on for about 15 minutes. Any thoughts?
Thanks

 

[bjohanson1234]

How old is the ballast? Sounds like it might be on its way out. How hot does it get? Might try increasing the air flow could be overheating.

Have you tried new lamps? Could be those also.