Electrical question

[Coleus]

My ballast has the following spec for 54W T5HO

Lamps Operated : 2
Input watts: 108
Line current: 0.96

Both light bulbs do not light up when I turn on, both are working on another fixture. So i use my voltmeter to measure the output voltage from my ballast to the bulb.

Base on the specification, am i expecting

54/0.96 = 57 V or 54/.96/2 = 28V ?

TIA

[wingedfish]

volts x amps = watts. Input and output will be slightly different do to losses to heat. The given is 108 watts out but the unknown is voltage and amperage. not to mention, i think there is a capacitance discharge to start the bulb.

I have no idea how to test the output of a ballast except to put in good bulbs. They can sometimes get week and not be able to fire older bulbs. If those same bulbs work in a different fixture, it's time for a ballast.

[lenzh]

Make sure the ballast is properly grounded. I had this problem when I was setting up my lights and it was frustrating. I had mounted the ballast on plywood in my light setup and so I needed to run a wire from the frame of the ballast to a common ground and voila, it worked

[Coleus]

this is the fixture so everything was properly wired. I bought a new ballast and replace it and it still does not fire up. For the old ballast, i see a flash in bulb so i know all connection are good. Just want to test to see if the new ballast is defective, so i test the output voltage.
Right now my volmeter reads only around 70 mV AC so i am thinking the new ballast is defective, my old one also read very low output Voltage as well

[banditpowdercoat]

ya the ballast is most likely dead. The reason for ballasts is to brovide a starting voltage, and yet limit current. Lamps, being Flourescent or MH (HID) they have a lot higher striking voltage than running voltage. Some bulbs take 600v+ to strike the arc, yet less than 100v to maintain the arc. I would be very carefull measuring the OCV (Open Circuit Voltage) with a meter rated less than 1000V.