Blown 1274 bulb?

Hi, had a Mag74 running on 7 1800's for few weeks now. Just noticed light was dimmer and looked at bulb. Inside of bulb has a white milky coating. I assume the bulb has blown? Why does it still shine if so? Only run bulb for maybe total of hour but turned it on and off lots of times playing with it. Does quick on and off shorten bulb even more? Thanks Love the light otherwise. Also, on a side note, I tried a stock 4d mag bulb in it with 6 1800's (7.2 volts) and it seemed pretty bright too. Anyone have any idea what the lumens using that setup would be compared to the 1274?

This is a sign that oxygen has entered the bulb. That would be caused by structural flaws in the glass envelope, most probably because of the potting process. Was this a potted bulb? Contamination on the bulb surface (i.e. in most cases fingerprint oil) can cause micro cracks in the bulb letting oxygen in. If you run the bulb a little more it will eventually turn dark grey as more of the tungsten deposits itself inside the bulb surface, and when run the glass will glow red. I had a potted 1185 this happened to.

Here is a thread you will find interesting.

Sigbjoern

Thanks. Yes, it is potted and it did happen like day after I was switching it and playing with stock bulb. I am sort of newbie but did wipe bulb off, guess not carefully enough though. This would happen with bi pin bulb too of not wiped off?

ok, well guess that is my problem...need to get some rubbing alcohol to get that finger oil off...glad I read this before I ruined my replacement 1274

I'd also add that lots of quick on-off cycles is not particularly good for high powered bulbs, expecially ones that are overdriven. I don't have any data to back this up but my instincts tell me that repeated cyclic stresses can be quite punishing. Because of the potting process, this might be aggravated. When I play with my lights, if I turn it on, I always run it for at least 10 seconds. In this way, even with the many bulbs I've used (including quite a few WA01274), I have only had a slow failure like that once or maybe twice. More often, they end up flashing or blowing up.

Wilkey