How to test Fluorescent Ballast

On Thu, 25 May 2006 11:59:40 -0400, RichK wrote (in article ):

The most obvious test would be to replace the bulbs. That would eliminate the ballast as the problem. Sorry if you tried that already, but you didn't mention it. Fluorescent bulbs don't last forever :-)

--
Nelson

Hi Nelson,

Yes, tried new bulbs - but it did not work. Was hoping that there is resistance check, or voltage.

I did do the normal web search and found some info, bo in all cases it says: replace the ballast. In fact I already did that and lights do work now. Ballasts are about $16 each locally to cover 2 bulbs.

Bonus question: Several places on the web mantioned that a ground connection to the fixture is essential for the lights to work. These have worked for 10 years without the ground - the original installer did not bring good ground to the lights.

Will lack of ground reduce the life of the ballasts?

RichK

No. If they start, then the ground is not needed for that. But there is the safety issue of any exposed metal parts that aren't grounded.

--- sam | Sci.Electronics.Repair FAQ:

Repair | Main Table of Contents:

+Lasers | Sam's Laser FAQ: | Mirror Sites:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Exactly. If say, a ballast developed an internal fault, the entire housing could become live without a ground there.

Graham

had a dubble 20w years ago brand new and the ballast was getting hotter than normal thinking that ok new fitting, went out came back home and found the 2 tubes exploded all over the bench defuser blowen off hanging one side. ballast shorted turn and to ground paint black on outside of fitting.

40 watt ballast for 2x20watt.

had a dubble 20w years ago brand new and the ballast was getting hotter than normal thinking that ok new fitting, went out came back home and found the 2 tubes exploded all over the bench defuser blowen off hanging one side. ballast shorted turn and to ground paint black on outside of fitting.

40 watt ballast for 2x20watt.

If you do replace it, go for an electronic high frequency ballast. You'll get more light with no flicker, the tubes will last longer and no starting problems.

--
*If a pig loses its voice, is it disgruntled? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Ballasts can deteriorate if the winding insulation breaks down. Older preheat twinlamp lead-lag ballasts also contain a capacitor in series with one lamp which can fail but yours is rapid start so that isn't the issue. Once one starts acting up you really do need to replace it though, many fires have been caused by failed ballasts. Class P ballasts contain an automatic resetting thermal protector but those can and do weld closed if they're left cycling too long.

As far as testing them, the only reliable test is to pop in a set of new tubes, if it still doesn't work and the sockets look ok then replace the ballast.

No, but without a ground the lamps may not start, especially if the humidity is high or the temperature in the room is low. Some lamps/ballasts seem less prone to this than others but if a fixture works sporadically then I usually check the ground first.