Checking Everything: Luminaires

Checking Everything: Luminaires

It's been a busy day, perhaps frantic is more accurate. The extra gear eventually turned up from the hire company; except that the 25 degree profiles turned out to be supplied as 11 degrees, which only meant de-rigging and moving about one third of the rig, after the LD was finally located, asleep on a couch in the foyer. Which was just as well, because it also gave you a chance to find out exactly why Lee 271 Mirror was listed as the colour in half of the FOH rig and to sort out what luminaire was represented by the symbol on the plan that looked like a flowerpot. It's time to start flashing out the rig. Aside from the 20% of the rig which has been wrongly patched, (well Les can't really help the fact that he transposed the dimmer and circuit numbers; besides everyone knows he has dyslexia,) about another third of the rig isn't coming up at all.

There's a fair chance that many of those luminaires weren't working before they were rigged and that quite a few others in the rig may turn around and bite someone during the focus. As it's so much easier to change the lamp, un-jam the focus mechanism, pull out the stuck decal, replace the missing shutter or get the melted gaffer tape off the lens while the gear is on the floor, why rig the gear until you've checked it out?

Some of the luminaires may be tagged as having been tested by a sparky[1] or an approved testing centre, but just ponder for a moment on what the tag means. Aside from the fact that it indicates that someone cares about the health of their equipment, a tag shows that at the moment of the test the luminaire had safe wiring and a good reliable earth connection. Unless that test was conducted right there under your nose in the last five minutes, it serves no real purpose for your rig.[2] Certainly regular testing is useful for keeping track of wear and fatigue related issues, but there is no testing process which can predict that a roadcase would be run over the luminaire's tail as it was being unloaded to be rigged, or that the lamp will blow after spending four hours on bumpy roads on the way to the fit-up. In the end, the only test that counts towards whether that luminaire is going to be safe and work for you today is the one you carry out immediately prior to rigging. ie. Assume nothing.

If you're going to test your luminaires safely there are a couple of procedures to follow. If at all possible, test the luminaires on a GPO[3] with earth leakage[4] (RCD, GFI, CBR, ELCB) protection or failing that, use a portable "safety switch" box or cable on your test cable. If you aren't certain that you are protected then you should avoid powering up a luminaire whilst you are either holding or touching it.

Don't leave luminaires powered up for prolonged periods if they're resting on a flammable or easily damaged surface. After testing a bunch of PAR64 cans it is not uncommon to find inexplicable circular marks on the floor: the electrics equivalent of the mysterious crop circles regularly featured on television specials about the paranormal. Whilst occasionally lending character to an otherwise uninspiring floor design, the circles are usually not appreciated by set designers and have been known to char wooden floors so badly that they have set off the smoke detectors. Especially avoid leaving fresnel or PC spots running with their barndoors closed, as the reduced airflow over the lens has been known to result in cracking.

The first step in the test procedure is to make an inspection of the luminaire: checking for frayed, damaged or melted cable tails or plugs. In the case of a parcan with an exposed ceramic EMEP connector, your inspection should include the cabling to the connector. If anything even slightly untoward is found, the luminaire should be pulled out of the rig at this point for repair or replacement with a spare (well, it's nice dream about having spare gear). There is no point in rigging a suspect luminaire, firstly because it may let you down, but more importantly because it may later become a lethal trap for some poor sod. Who knows, it may even be you who's up the scope focussing at the time.

Although it's not a safety issue, the next step in your test ought to be to check that focus mechanisms move freely, that shutters are (a) present and (b) actually move, that barndoors or snoots are firmly attached and rotate as required and finally that there is no gobo left in the gate or gelframe in the colour runners. (Don't forget to re-tighten the locks on those slide focussing lenses and lamp trays.) It's quite amazing how often a luminaire with a piece of Congo Blue or a small leaf breakup gobo fitted is mistaken for being dead when flashing through the rig under full worklights.

If the luminaire has made it this far through the check, it's time to power it up. Do not hold on to the luminaire, don't even touch the body at this point. Plug it in to your known working (and hopefully, protected) power supply and listen carefully for sizzles, pops or bangs. If all appears well, touch the back of your hand very gingerly on an unpainted surface of the luminaire such as the suspension bolt or the hook clamp. If the body of the luminaire is live, your hand will be kicked safely away by the potential causing a brief muscle spasm. This is preferable to having your hand spasm and lock around the luminaire while you are electrocuted. If all is well then you have probably got a luminaire which is both working and safe to use.

Oh, and don't forget to open the shutters or barndoors as soon as each luminaire is rigged. Luminaires are generally more effective if the light actually gets out at the front.

[1] Electrician

[2] This is not a criticism of testing and tagging, rather a warning that testing alone doesn't guarantee reliability and safety. If you know of a method of predictive testing which takes accidents into account, please contact Connections because we would be interested to write an article about it.

[3] General Purpose Outlet or power point

[4] For more information on earth leakage protection, read this article.

by Andy Ciddor
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