Author Topic: Did the Metal Halide ballast do this to the lamp?  (Read 831 times)
valvashon
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Did the Metal Halide ballast do this to the lamp? « on: April 30, 2019, 09:09:46 AM » Author: valvashon
I'm repairing the sign lights here at the TV station I work at, where I'm a maintenance engineer and also have been handed the building maintenance duties.  These are long neglected 150 watt Elliptipar fixtures; I now have 4 out of 6 working; all needed new lamps and I have had to replace all of the capacitors and some of the ignitors.  All of the transformers so far have been good.  I did pull one completely down to put new sockets into the fixture and to have a test ballast in which to swap out components. 

My latest repair involved the middle fixture on the unlit side of the sign.  My first move was to put a new lamp in to see if it would light.  It did not so I knew I needed to repair the ballast.  These are CDM-TD 150w/830 tube style lamps.  The capacitor was relatively new (April 2017) and tested out at the proper 16.0 uF.  Ignitor was bad so I replaced it with one from Keystone; Keystone ignitors are in two of the ones that are currently in working order.  On my test ballast I hooked up both the capacitor and ignitor I eventually used in the "middle fixture" and they lit the test fixture lamp just fine.

Wired the new components into the transformer in the middle fixture and upon powering up, found that the lamp was flashing weakly.  I gave it plenty of time to warm up but it just never did.  Upon removal of the lens on the fixture I discovered that the formerly new and undamaged lamp looked like the first picture- burnt at one end with the inner envelope somehow crooked and with two little round balls of metal rolling around inside.  I handled this lamp very carefully and don't think I damaged it during handling or installation.

I put this lamp into the test fixture and it lights as you see in the second picture- at the connections to the inner envelope and around the outside of same.  I made a video of this and it shows some flashing too, as if the whole envelope is trying to fire instead of just the inner one.

Third picture shows a new lamp and #4 shows how a new lamp lights up- a slight blue glow at the ends but an inner envelope lit up.

So my question is this- did that newly repaired ballast "eat" that new lamp I put in it or did I have a dud lamp that would have failed in that manner in any fixture?  I have a lamp that's in working order (the one you see in the photos) but I'm somewhat reluctant to install it in the newly repaired ballast until I can figure out why the other one failed.  I'll check my wiring, of course, but I don't want to avoid ruining any more good lamps; they aren't terribly expensive but I don't want to waste company money experimenting on this.

Thank you-

Val
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dor123
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Re: Did the Metal Halide ballast do this to the lamp? « Reply #1 on: April 30, 2019, 12:50:53 PM » Author: dor123
If your brand new ceramic metal halide lamps, experiences a discharge in the outer jacket, there is a manufacturing flaw in the arctube seals that allows the content inside the arctube to leak into the outer jacket.
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valvashon
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Re: Did the Metal Halide ballast do this to the lamp? « Reply #2 on: April 30, 2019, 06:06:42 PM » Author: valvashon
Thanks for the tip.  Turns out it was just a bad lamp.  This is a picture of a new lamp in the fixture.  I ran this lamp for about an hour in the test fixture then put it in the mounted one today.  That's my gloved hand holding down the safety switch.  I did that so I could have some control of the fixture if the new lamp started acting weird.  Out of focus picture but you can see the inner envelope is lighting, not the outer one. 

Thanks for the help.
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