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Fault Finding Help... Fluoro Tubes....


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Hey Ladies and Gents,

Wonder if you could help me. I work in an Arts centre in North Finchley, and we're having a couple of problems with the |FOH lighting equipment. Cleverly, they dimmers were installed by a company from Australia, so obviously a call out will be expensive!

Basically, I would like to know how that I can check that the fittings for the fluoro tubes are still working, am I able to do this with a multimeter? If so, please could you let me know how as nobody within the building is entirely sure how! The fittings each hold two, thin 5ft Fluoro tubes (I can let you know which type exactly, if needs be).

If you could please let me know how I can check the unit that would be most appreciated, as we have exhausted all other faul possibilities and would rather not get a sparky in!


Many thanks in advance for your help,

Kind regards,


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Can you describe the actual fault symptom(s)?

(Eg flicker, no light at all, very long strike time, buzzing like crazy...)


It's rather difficult to fault-find if you don't know what the fault looks like.


There are a lot of things that could go wrong with florries - from simple tube failure, to ballast failure or even a simple 'no power supplied' issue (eg breaker trip, SCR/relay failure)


After that, we'll need to know what kind of fluorescent ballast - non-dimmable, or dimmable, which kind of dimmable (two-wire, three-wire, four-wire, 0-10v, 1-10v, DALI, DSI etc),


The first thing to check is the obvious "Is it getting any power?"

You can usually check this with a good RMS voltmeter at the input terminals of the fitting - don't try to measure the output terminals where the tube fits, the voltages here are strange and can be high.


- Most cheap multimeters will lie to you, but they will at least show the difference between 'no volts' (under ~30VAC) and 'full volts' (~230VAC)


One thing to remember is that no fluorescent light will successfully dim below around 15 to 20% - the majority come on at around 20-30%.

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Thanks for your replies.

As for your questions:


There are approx 80 florries, wired in parralell. There are four sockets feeding power to them, 2 of which are emergency lighting fixtures which should come on when power fails or is removed, but these are not working either.

There is deffinately power going to the units and the circuit is deffinately live. All breakers and trips have been checked, tripped and reset to see if this will solve the fault. As for the unit themselves, they do not have a ballast and are controlled by a control pannel, with different pre-programmed states including different intensities, so I guess this would mean that they are dimmable. All obvious things such as power, ballast, breakers have been checked but no no avail hense this post.


As for the florries, they are not flickering or starting up at all. They do not have a starter or ballast as previously stated, so this is not the problem. So there is no strike time and no buzz at all. All of the bulbs have been replaced with brand new tubes, so this cannot be the problem either. One of the lines is working fine, but the other three aren't (hense the 4 sockets, but their is no conceivable problem with them).


As such, we were just wanting to check each of the units themselves to see if their is a faulty one, but even so if there was a break or problem with the current, the breakers should have kicked in, but this is not the case... hense why we are so confused....


Any suggestions or help would be greatly received.


Many thanks again...

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All linear flourescent lamps have ballasts, in the case of dimming or other special features, these may not look like standard ballasts, and may be mounted somwhere remote and/or inaccesable.


A good starting point would be "did the defective lamps all fail at the time time?, this suggests a wiring or control fault, or did they go out one by one over months or years ? which would suggest a steady failure rate of ballasts or other components"


From each lamp you should have four wires, two from each end, these will go to the ballast which will have at least two other wires to it, the live and neutral mains supply.

There may also be an earth wire, but not allways since sometimes reliance is placed on the fixing screws to an earthed enclosure.

In the case of a dimming ballast there will be additional connections.

If the ballasts are remote from the lamps it would be worth testing the wiring between lamp and ballast, not just for short or open circuits, but for wires crossed over from one lamp to another.


Having located the ballasts, it would be worth replacing one and seeing if the lamp lights, dont waste money at this stage on a load of ballasts in case the fault is elswhere.


(you have a PM)

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