I have a Philips Lifeguard (not Westinghouse, so a later model) that was installed in dusk-to-dawn operation on a metal halide ballast. The lamp is H39 and the ballast is H39/M57. It lasted six years in service and then suddenly wasn't working. I replaced the PC first and when covered, the ballast would hum. I then replaced the lamp and the new one works. The arc tube, from what I can see (it is a completely coated BT28), is white. Brightness wasn't much lower than when new.

I expected this lamp to last longer than six years, and to get much dimmer than that before failing. I am wondering if operating H39 lamps on M57 ballasts will shorten them somehow.

I replaced it with a M57 protected lamp. I don't expect much more than two years from that one. I'd have put another MV but I was kind of in a hurry and the MH were closer...

I believe it ran closer to 24 000 hours. It ran more than 8 hours a day for most of the year. The power company here calculates unmetered street lights at 4 000 hours per year (which would be 24 000 hours in this case). Still with a Lifeguard MV, I expected more...

You're right about a weak lamp. It might just be that. I only have one in service so there is nothing to compare against it.

Oh, and in case it matters, it is a CWA ballast that is rated M57 (and H39, too).

Probably a bad connection inside the lamp, try tapping it while its on.

Climbing a 16-foot street light pole is not one of my favorite hobbies. The new MH lamp in there will most likely stay until EOL. I might, on another (more accessible) ballast, try it again, when the time permits.

I have a Philips Lifeguard (not Westinghouse, so a later model) that was installed in dusk-to-dawn operation on a metal halide ballast. The lamp is H39 and the ballast is H39/M57. It lasted six years in service and then suddenly wasn't working. I replaced the PC first and when covered, the ballast would hum. I then replaced the lamp and the new one works. The arc tube, from what I can see (it is a completely coated BT28), is white. Brightness wasn't much lower than when new.

I expected this lamp to last longer than six years, and to get much dimmer than that before failing. I am wondering if operating H39 lamps on M57 ballasts will shorten them somehow.

I replaced it with a M57 protected lamp. I don't expect much more than two years from that one. I'd have put another MV but I was kind of in a hurry and the MH were closer...

When was this lamp made? Philips has bad welds in their later designs, and an otherwise perfect lamp will prematurely fail. I've seen this before, especially with their HPS lamps.

Sounds like a fluke.  The NOS LifeGuard lamps are still all over eBay to this day; most last forever.  I know some later model Philips BT28 ones in a few places burning presumably every night since the mid-late '80s in older blaster lights.

Yes, I’m dismissing this as a fluke. I have a few Lifeguard lamps and I might try one when the current MH one fails.

i have a 86' Phillips lifeguard installed in a yard-light (dusk to dawn) at the church and its been going for 6 months so far its a ED shape, will report how it does