Author Topic: New to Ceramic Metal Halide lamps, could use a little help!  (Read 2380 times)
Brendda75
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New to Ceramic Metal Halide lamps, could use a little help! « on: June 14, 2014, 05:04:41 PM » Author: Brendda75
Hello everyone, I have purchased a small box of JUNO track lighting fixtures that use the CDM Philips lamps.  I have such little knowledge about these lamps, I am just wondering if someone out there could steer me in the right direction as far as being able to get an idea of how used they are or at EOL?  Out of the 6 fixtures, 2 were bad, one was EOL, and the other suffered an arc tube rupture about a minute into warming up suprising me with a "ting" sound.  I do plan on going back there sometime soon and pick up more of these, but I wanted to get an idea what to look for so I don't get a fixture with a bad lamp.  The other 6 lamps that I have appear to have a LOT of yellow in the arc tube, where as the the one that is EOL has no coloring, just a dark band on one side.  I would appreciate any help!
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sol
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #1 on: June 14, 2014, 06:12:32 PM » Author: sol
Welcome to CMH world !

Mine have the yellow stains on the arc tube. I believe it is the deposits of metal halide salts that vapourise during the warmup. They were like that when new.

Be sure to operate the G8.5 lamps in a fully enclosed fixture as an arc tube rupture at full pressure would break the outer bulb and send hot pieces of glass everywhere. My metal halide fixture uses a G8.5 lamp and makes a very good not-too-intense light source. Of course it has a full lamp shield. I use a Philips MasterColour 941 lamp and it produces nice crisp white light. Someday I might get a 930 or a 830 lamp to make a halogen-like colour.
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #2 on: June 14, 2014, 07:11:06 PM » Author: Brendda75
Thank you sooo much sol!  I never was into HID lamps until I see photo of other members on here such as FrontSideBus, some of our members in Australia, and of course, Danny as well!  If it wasn't for them, I wouldn't have been interested in these HID lamps!  I do have to say that these little CMH lamps are very interesting to watch run up!  So blue when first turned on then right at the end, the color shifts to Warm White!  And hot little things they are!


So, yours have the yellow stains on the arc tube as well?  I wonder why the one that I have that is EOL has no stains, just black.  I am pretty sure that most of the lamps are most likely to be a 3000K color as well since they all appeared at one time.  Maybe I should look for ones that have the yellow stains and of course the blacking as well.  I just want to get another box or 2 of these fixtures so I can have some spare lamps as well as the ballasts, and I am sure that there are a few members here in the gallery that may be interested in a fixture or 2.

My JUNO fixtures have warnings all over inside of the fixture where the lamp is, especially with the UV.  Has a big sticker inside saying that the lamp MUST have a UV approved barrier otherwise people may get sunburns and the like.  I thought these lamps the outer envelope would do the UV blocking?  I have noticed that on mine, when they first start up, glow a blue until the lamp warms up some.  An no worries, I will be keeping the reflector on when in use!  I had an arc tube rupture on me already and it scared me with that "ting" sound with me about 2 feet away from the lamp!
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #3 on: June 15, 2014, 02:10:45 AM » Author: Medved
UV shield: Only small wattage lamps suffice with the outer as an UV barrier. The thing is, as the lamp requires the mechanical shield anyway (so thick enough front glass), it is easier to utilize this glass as the UV shield, than mess up with doping the outer quartz and so reduce it's strength.

Yellow stuff vs EOL: The stuff inside the arctube are indeed the halide salts. Normally, once the lamp warms up even a little, it melts, when fully warmed up, it partly vaporises (at the end it is the vapor of this stuff, what generates the light in the arc).
So once the tube had ruptured, the liquid contend had splashed all around (and most likely formed a kind of fog and then thin coat on everything), so it isn't in the arctube anymore...
Such stuff (it could differ in color) you will find in any MH lamp, not only ceramic.

And how to recognize a worn out lamp? Without powering them up it is quite difficult, so do not expect any more reliability than just guessing. Normally the EOL lamps are assumed when either their rated life is over, or they change their color significantly, or start to cycle, or have exploded. The arctube explosion in CMH isn't as violent as with QMH (good outer should contain that), it is even not a typical EOL for the CMH. The cover is needed due to another reason: Normally the arctube leaks at EOL, what may allow a discharge do form in the outer between the lead in wires and other structures there. And it is this discharge, what locally overheat and break the outer bulb into pieces, sending them all around. But the discharge in the outer is quite readily visible. But you need a good reference lamp to identify that happening correctly. As the disc harge in the outer has different electrical characteristic, some electronic ballasts are designed to recognize it and shut down. This will save you from cleaning the glassy mess, but the protection cover is still necessary - the detection method isn't bullet proof...

But you may try to look inside:
- In ceramic MH, the main aging mechanism is the liquid salt mix attacking the arctube wall. So if you would see the brownish stain residing in irregular cavities, it was probably quite used. But the problem is, the arctube is not transparent and the wall is not of the same thickness everywhere (with some designs on purpose - to keep enough material for the salts to chew through where the salt pool is sitting and to not block the light on other places)
- Generally blackened  arctube: The material from the electrodes sputter around with each start. But normally the halogen cycle cleans it up back. So a black arctube could be just an arctube experienced incomplete warmup during the last power up, which would normally clear once it would be allowed to warm up fully. So even perfectly good lamp could be sometimes temporarily black and work well when powered up again...

More reliable signatures are those of arctube leaks:
- Stains in the outer, mainly close to arctube (but do not get fooled by the getter deposition, that is of course normal)
- Discharge in the outer (but do not get fooled by the bluish fluorescence of the UV-stop quartz)
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #4 on: July 06, 2014, 02:49:40 AM » Author: lights*plus
Hello, any updates Brendda75..?? Did you go back and get the rest?
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #5 on: July 06, 2014, 04:40:46 PM » Author: Brendda75
@Medved:  Thank you so much for all of the information!  And you are right, you really can't tell if the lamp is okay or not just by looking at it.  But still, learned quite a bit of information on these lamps from you!

@lights*plus: I did get some more of these fixtures and were posted in my gallery!  I only got the 3 out of 5 boxes left since I went through all the boxes to get ones that seemed to be okay.  Several of the fixtures were damaged either with broken lamps or the actual glass in the front were shattered.  All the ballasts work, just lamps were either EOL or ruptured on me during testing.  I do have 5 fixtures though that is available for trade.
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #6 on: July 07, 2014, 08:00:33 PM » Author: lights*plus
@lights*plus: I did get some more of these fixtures and were posted in my gallery!  I only got the 3 out of 5 boxes left since I went through all the boxes to get ones that seemed to be okay.  Several of the fixtures were damaged either with broken lamps or the actual glass in the front were shattered.  All the ballasts work, just lamps were either EOL or ruptured on me during testing.  I do have 5 fixtures though that is available for trade.

Hi Brendda75,
What do you need? I have many HPS items I'll like to reduce.

I'll send you 2 (two) HPS ballast kits (normal-power-factor, any wattage up to 150w) for 1 (one) fixture with ballast, shattered glass in front acceptable.

Or 1 complete HPS fixture for 1 of yours. See 35w & 70w units attached, lamps included. PM please.
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #7 on: July 09, 2014, 09:13:21 PM » Author: Brendda75
Hi lights*plus!

Oh, I do not have a single HPS ballast kit at all, and I do want to start collecting them.

And to note to everyone on here, all of these fixtures are complete, even with the front glass.  I left all the ones with the broken glass at the Restore.
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Re: New to Ceramic Metal Halide lamps, could use a little help! « Reply #8 on: July 09, 2014, 10:59:56 PM » Author: lights*plus
I left all the ones with the broken glass at the Restore.

Actually, if the fixture/ballast is good, the glass isn't imperative (at least to me) and it can be replaced..So go back and get them!
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