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More fun with summer stock electrics...

Discussion in 'Lighting and Electrics' started by Grimtheatre, Jul 10, 2008.

  1. Grimtheatre

    Grimtheatre Member

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    So in my never ending adventures with my current job as an ME at a smaller barn summer stock i've come across a lot of problems. The latest is an increased amount of carbon build up on lamps and in caps of our lights. Granted part of this is because the previous ME used HX-601's in old colortrans and we can't afford new lamps, but the power set up itself looks to be interesting as well. We have 4 ETC smartpacks (1 12-circuit and 3 6-circuit) and an NSI DS12. From the dimmer room which is set off from the stage what are essentially just long extension cords run power out over our grid and into power strips which are essentially strips of metal housing with twistlock sockets every 3 feet (from what i've seen the wiring in here is about 20 years old at least). Now i understand that you'll get voltage loss over a longer run, but when i took a voltmeter to one of the sockets it read at 90 volts. Am i right in assuming that this power loss is what is causing the carbon build up on the lamps and in the caps? Any thoughts on these issues is as always appreciated!
     
  2. Grog12

    Grog12 CBMod CB Mods Premium Member

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    Wait....why would HX-601's increase carbon build up?

    The lamp not being seated properly would....
     
  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Those "power strips" are called "raceways" and are most likely the correct item for your application. I've worked in theatres with sixty year-old wiring that was perfectly safe and acceptable.

    As [user]Grog12[/user] said, low voltage is not causing carbon buildup on your lamp pins and sockets--that is the result of arcing, due to lamps not being seated correctly/fully. Once a lamp and socket begin to arc; putting that lamp in a good socket; and/or putting a good lamp into a different socket, causes the disease to spread, and before long, you have an epidemic. Time to call CDS (Center for Disease Control, not Cirque du Soleil). Replace all bad sockets immediately, and discard all lamps that show evidence of charring on the pins. Some will tell you the lamp's pins can be cleaned with emery cloth, but this will only made the pins smaller, leading to even more arcing, and is a temporary solution at best.

    Have you metered the power going into your dimmers? Are you using a True-RMS meter to measure the output voltage at the fixture? What gauge and length is the wire of your "extension cords" (most likely multi-cable)?
     
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  4. Grimtheatre

    Grimtheatre Member

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    I didn't think the incorrect lamp was causing the carbon but does make the lamps blow sooner right?

    The wiring in the raceways appears to be 12-gauge and while i didn't give it a second thought the electrics in this theatre have been very poorly maintained. I only had a digital multimeter when i was testing the voltage but after talking to the artistic director he's having the electrician who installed the system come take a look at it (electrical engineer i am not).

    Poorly seated lamps is most likely part of the problem (as well as cleaning the pins on the lamps as per instruction by the TD/LD). And while i would love nothing more than to replace all the lamps and caps that show evidence of charring, the cold hard truth of the matter is i wouldn't have any lights then (like i said the instruments have been very poorly maintained and at least half of them have carbon build up). I have no budget thanks to preseason crap they tagged onto my budget so my options appear to be very limited... woohoo
     
  5. icewolf08

    icewolf08 CBMod CB Mods

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    If you are constantly getting 90V at the raceways then there is something wrong with your system. I would take a meter to your power feed to the dimmers and see what that reads. You shouldn't be loosing 25V-30V to cable runs (unless you are using severely under-rated cable). If your input power is reading correct then chances are you have some setting wrong either in your dimmers or in your console that is keeping the dimmers from going to full.

    As far as the carbon build up, it has nothing to do with the choice of lamp. A medium bi-pin lamp (like the HX-601) is a medium bi-pin lamp. It is possible that your fixtures may not be rated for certain wattages, but that would not cause extra carbon build up. Using the HX-601 (FLK) in a colortran shouldn't be a problem, it is a 575W lamp that should be well within the tolerances of the fixture. However, in the future I would suggest the HX-604 (GLC) if you want to stay in the 575W lamp category, as it has a much more modern and efficient filament.

    Inevitably, at some point in every fixture's life you will start to see carbon build up on the lamps and in the lamp base. Why? Because all the cycles of heating and cooling and the changing of lamps start to wear on the contacts in the lamp base. As the connection between lamp and base deteriorates you start to get arcing, and this produces the carbon deposits. Now, if you are getting build up like this in the lamp base you will start to go through lamps faster as it carbon deposits beget more carbon deposits. Many people perpetuate this because they see that a fixture is out, and so they change the lamp. Then the fixture works for a while, but while it is working carbon is building up on the lamp and eventually not electricity can pass, and thus another apparent burn out. So, if you open up your fixture and there is a lot of build up in the lamp base then you NEED to replace the lamp base. DON'T put new lamps in bad bases, it is a waste of money as the lamps weill become unuseable long before they should. Lamp bases are relatively in expensive and pretty easy to install.

    I bet this is your issue, so I would look into picking up some new lamp bases and you should be in business.
     
  6. icewolf08

    icewolf08 CBMod CB Mods

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    Not necesarily. If you used a lamp that was too high a wattage for your fixture, you may have lamps die prematurely due to the fact that the fixture can't get rid of the heat fast enough. In your case it shouldn't be an issue.

    Your multi-meter may be True-RMS, it would say on it somewhere (or tell us the model and we will let you know).

    Cleaning the pins or the contacts in the lamp bases is a big No-No. Why? because no matter what you use, be it a file or sand paper you are removing material from the pins. Then you have pins that are too small for the contacts in the base. This is bad because it is just another way to create ideal conditions for arcing.
     

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