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Discharge lamp holders corroding


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Hi BR.


I have a couple of Robe scans which over time, have been corroding the pins that hold the lamp (575W double ended discharge). I'm talking about blackened metal lamp ends, where the metal pins have corroded and on one of the scans, one end of the discharge lamp has actually bent around, causing the screw pin and pin holder to fuse together and now I can't get it out. The lamps though still work fine.


I know this can happen sometimes when a lamp isn't screwed in properly - like constant arcing. But I put these lamps in really tight.


Could it be a heat issue? Could it just be that they are coming loose and arcing? Ill need to change the metal contact holders anyway.





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it is arcing causing the damage, and it is fairly common on double ended lamps and their holders where the lamps are not put in tight enough and not checked for tightness often enough.


All my movers are on double ended lamps - HMI 1200w/GS and HTi 1200w D7/60. After having occasional problems with this when heads have been out on hire for longer periods, I now give the lamp base nuts a GENTLE tweek with a pair of pliers when installing, which seems to remove any problems. Please be gentle though, to much and your new lamp is in bits!


Im sure that older double ended hmi lamps used to be supplied with a spring washer behind the nut - but no longer?

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Agree with CSG, they are prone to arcing. Its a slippery slope; a bit of tarnishing can pit the contacts and then no matter how hard you tighten the lamp, it'll run hot and possibly arc some more, getting worse over time.


I don't know what the experts think but zinc-oxide heatsink compound is sometimes used on industrial high current connections to minimise the risk of poor-contacts developing into hotspots, this might be worth a look into.


In any case, make sure the burnt contacts are either replaced or cleaned, filed and inspected closely everytime you relamp. Coming originally from a disco environment, we used to get this alot on the reverred TAS Synchro, sometimes the lamp-ends would be ruined by the lampholder long before the lamp capsule expired if this wasn't seen to.

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