Need advice from lighting gurus
 

I have a ballast from an old 2x 55w pc fixture.I'd like to use in a T5 retro Im building,but Im not sure how many T5 bulbs it will run.

Its a 34EF balast approved for 2x 55w pc or 2x F40 T12.
I'll be running 24w T5s Can I run 4 of them with this ballast?

check the website for the ballast's manufacturer, and see if there's a wiring diagram for T5 HO. It'll tell you how many bulbs can be wired for that ballast, and how.

what's the model # of the ballast, and the manufacturer?

Not sure of the manufacturer,its an All-glass model #200 electronic

maybe look around the wiring diagrams for other manufacturers, and see how they show to wire T5's on their universal ballasts. maybe there's one that looks like your's you can mirror. Might work.

It's an electronic though, right? don't know if a magnetic would work on anything other than what it's designed for.

Ya its electronic.Made for running 2 40-55w bulbs,so it has 2 sets of wires.Maybe I'll try running 2 24w T5s off one set of wires and see if they will work.If so, then I'll try 2 bulbs off the other set.If I have to I can always get the proper ballast if this one wont fire them all.Looked around google and all I could find were ppl looking for replacment ballasts for this one.

maybe check manufacturers of advance, workhorse, universal and such, and see if they have one with similar specs and the same leads coming out of it, then mirror the wiring diagram for that one?

It probably won't fire HO T5s at all, they're tricky little beasts.

yeah, heard they run to the labour board at the slightest threat :D

I have a coralife HQI/pc combo and I was looking at the ballast. the pc ballast has the same rating as a t5 ballast I have(120v ac 60Hz) except that the pc's are 96 watt and the t5s are 55watt. I was wondering if i could use the pc ballasts with the t5 bulb adapters but haven't gained the courage to try it on such a pricey fixture though it would be a nice upgrade..