Troubleshooting a T5 Ballast

[bbyatv]

Can anyone tell me how to check and see if a T5 ballast is working by using a multimeter?

 

If I use a multimeter to check the thing out, what wires (blue, red, yellow) should I place the probes on and what voltages should I get out?

 

Thanks for any help.

 

Bruce

[dchild]

disclaimer: I have no formal training in this. Follow my advice at your own risk.

 

I don't think your typical multimeter will do what you want it to do. Electronic ballasts run lamps at very high frequency AC (well, high compared to the 60Hz from the wall), and they are "load-sensing", so they will provide higher voltage at startup and adjust themselves depending on the number of lamps connected. You won't get an accurate test unless it's under load. (For example, if you were to test a "wall wart" power supply at no load, it will show a much higher voltage than it actually gives. Give it a load, and it drops down to about where it should be.)

 

So you want to test it by hooking it up (use a GFI outlet!). If you have T5's, PC's or VHO's, these will all generally work on a T5 electronic ballast provided they are in the right wattage range. (If they don't work, I believe they simply won't light, and there is little risk of damage to the bulbs). The electronic T5-rated fluorescent ballasts are amazingly flexible and will usually work with most combinations of bulbs up to their rated wattage.

 

"Normal" fluorescent light fixtures work too. (NOT the screw-in CF lightbulbs!). Home depot/Lowes will sell you a 4' shop light for <$10, or a smaller one for about the same price. Also perfectly reasonable to buy a fluorescent bulb and the end caps (<$5), wire it up and you can test it without a fixture. Be careful to keep it safe (use a GFI, do not let any bare wires touch anything they aren't supposed to, wear goggles, and stay away from flammable substances).

 

If it does not work, it is most likely either (a) completely dead or (b) shorted out. In the former case it just won't light, and you can set your multimeter on the highest AC setting and see if you have any voltage at all (test from yellow to either red or blue. It's AC, so polarity doesn't matter). In the latter case, it will trip the GFI.

 

Good luck, and be careful!

 

Steven

Edited December 16, 2007 by dchild

[bbyatv]

Stephen,

 

Thank you very much for your detailed reply. I truly appreciate your time and advice.

 

Bruce

 

disclaimer: I have no formal training in this. Follow my advice at your own risk.

 

I don't think your typical multimeter will do what you want it to do. Electronic ballasts run lamps at very high frequency AC (well, high compared to the 60Hz from the wall), and they are "load-sensing", so they will provide higher voltage at startup and adjust themselves depending on the number of lamps connected. You won't get an accurate test unless it's under load. (For example, if you were to test a "wall wart" power supply at no load, it will show a much higher voltage than it actually gives. Give it a load, and it drops down to about where it should be.)

 

So you want to test it by hooking it up (use a GFI outlet!). If you have T5's, PC's or VHO's, these will all generally work on a T5 electronic ballast provided they are in the right wattage range. (If they don't work, I believe they simply won't light, and there is little risk of damage to the bulbs). The electronic T5-rated fluorescent ballasts are amazingly flexible and will usually work with most combinations of bulbs up to their rated wattage.

 

"Normal" fluorescent light fixtures work too. (NOT the screw-in CF lightbulbs!). Home depot/Lowes will sell you a 4' shop light for <$10, or a smaller one for about the same price. Also perfectly reasonable to buy a fluorescent bulb and the end caps (<$5), wire it up and you can test it without a fixture. Be careful to keep it safe (use a GFI, do not let any bare wires touch anything they aren't supposed to, wear goggles, and stay away from flammable substances).

 

If it does not work, it is most likely either (a) completely dead or (b) shorted out. In the former case it just won't light, and you can set your multimeter on the highest AC setting and see if you have any voltage at all (test from yellow to either red or blue. It's AC, so polarity doesn't matter). In the latter case, it will trip the GFI.

 

Good luck, and be careful!

 

Steven