no....for a 2ft T5....the wattage for high output tubes is 24w...and the electronic ballast can be used for 2 tubes....
i think the 50w ballast can fire those tubes up...only think is the tubes or ballast lifespan will be shorten...
what i know is a higher wattage ballast can fire up a tube that is equivalent or lower wattage den the ballast...
but if the ballast is 24w...there is no way its gonna fire up a 39w tube...
hope u understand...