UHE (E-TORL) bare bulb polarity?

Discussion in 'Displays' started by Akro, Jul 11, 2011.

  1. Akro

    Akro Auditioning

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    Do these bulbs have a polarity? Or, does it matter which lead goes to which post on the connector? I recently purchased some bare bulb replacements for my Epson HomeCinema 1080UB, which takes the ELPLP39 lamp. I had a previous cartridge with a blown bulb in it, so I got a set of 3 of these bare bulbs to rotate through the two cartridges I have. Upon closer inspection of the bulbs, I see that the 2 leads coming from the front center of the lamp (where the thin glass bulb is located) and the rear center of the lamp (where the ceramic is located) are not always wired to the same post on the connector. The connector will only fit into the cartridge/housing in one orientation, having the "larger tab" facing outward (toward screen, or "front"). One bulb may have this "large tab" post wired to the front of the bulb, while another bulb will have this post wired to the back of the bulb. So my question remains... Do these have a polarity? Does it matter if the front or the back of the bulb is wired to the "large tab" post, or vice-versa? Or are these bulbs strictly AC, in which case it shouldn't matter? I realize that the connector must be positioned correctly within the cartridge in order to be inserted into both the cartridge and the projector itself, but if the leads are reversed on the connector-to-bulb front/back wiring, do I risk damage? Thanks, Akro
     
  2. Leo Kerr

    Leo Kerr Screenwriter

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    Hm. Interesting.


    I know xenon lamps are polarity sensitive -- DC arcs.


    I kind of suspect that the smaller lamps are DC arcs, but I don't know that for certain.


    While I am not an expert, however, I offer this suspicion: if the polarity matters, and you get it wrong,


    a. the light may not be as bright (or not work at all,) and

    b. it shouldn't hurt anything if you only run it a short period of time.


    But that's a guess. Since the manufacturer seems to be inconsistent, I'd bias toward it not mattering.


    Leo
     
  3. tv-tech

    tv-tech Extra

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    My understanding was it was a high frequency AC driving the lamps. I don't remember where I heard that, but assuming that is correct, no it wouldn't matter.
     
  4. Leo Kerr

    Leo Kerr Screenwriter

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    the only place I'm familiar with the high frequency AC is during the initial ignition phase in a Xenon arc.. where they ionize the xenon by pumping it with several megahertz HF, HV, no current, before blasting it with the high current DC... I'm not familiar enough with these "tiny" lamps, though, to know the details.


    Leo
     
  5. tv-tech

    tv-tech Extra

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    That very well could be the case. I asked one of the RBM's for one of the manufacturers when they first started selling them. I have had more than one case of a manufacturer rep. having no idea how they actually worked,,,,and as a tech it was really never that important to investigate. I always pay attention to polarity when I install them,, just easier to put them back the way I take it out.
     

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