Degrading performance on Phillips discharge lamps

[timmeh2]

Hello BR

 

Another inept post from myself.

 

A couple of years ago you could pretty much guarantee that any Phillips lamp would last to, and in most cases, past, its rated life. However recently I've noticed that this is no longer the case. Several times I've had to send lamps back because of misshapen envelopes and/or the electrodes being out of alignment. All to often they warp sideways which pulls the spark gap apart leading to crap performance and also gives the ballasts hard time. This seems to be across the board as I use MSR700 and 1200DE. I've also noticed 575-powered kit coming back to me where the lamp has let go unexpectedly early.

 

And it's also annoying that you no longer get the handy alcohol wipe so I have to carry a can of IPA around with me.

 

Today is no exception to the rule and I've got one where the upper electrode has cracked and failed, at 320 hours, so about halfway into its life. The envelope is clear but is showing distinct warp as the electrodes are about 3mm apart in the horizontal plane, which is almost beyond the point where it'll stop working. Maybe the electrode failed because the ballast was driving it harder, although I have electrickery ones that clamp the voltage to around 80V when running.

 

There was a time when you could only stick MSRs in your VL2500s but it seems that GE have changed the spec for the CSR a little so they could now be used, so I'm sorely tempted to have a punt at one and see how things go.

 

So, the question is, has anyone else noticed this with their fixtures? Or is it a problem specifically limited to Varis? I know that they aren't the greatest in terms of cooling and do run biblically hot, and the VL2000 even more so, I'd be interested to hear of your experiences.

 

All the best

Timmeh

[itiba]

Funnily enough Philips Varilight don't recommend Phillips branded lamps for the first choice in their units - they recommend the Osram SharXS range IIRC, whether it's for reason you describe I'm not sure but if you're doing basic stuff like lamping off an leaving a cool down period and not putting great muddy finger prints on the glass it might be worth changing your lamp manufacturer.

[bigclive]

I know that it's not common practice, but when we have a shed-load of VLs at the Tattoo we routinely walk along the gantry during the show and check the backs with a thermal imaging camera. The temperature variation is HUGE and while that's partly due to the amount of time the shutters open during the show, and the lamps running at full output, it can also be down to things like dead fans and even misplaced wiring looms in front of fan ports. Particularly the internal air stirrers on the gobo/colour assemblies.

 

There's also another issue that has been known to rear its head in the past. The electronic ballasts share common housings within large sections of the VL range, but some are set up for a higher lamp wattage. There's no "universal" ballast for them all, and sometimes the wrong ballast gets put in and overdrives the lamp. And it's not as simple as looking for the "bright" one as the variation between different fixtures can be quite surprising when lamp life and dust is factored in.

[timmeh2]

Hi Clive

 

I can't say that I've ever even considered using a thermal imager to check out a rig but it sounds like an interesting idea.

 

I've seen the ballast issue once IIRC with a 2500 configured for 1200W output. Maybe it was a friday afternoon in the factory or something.

 

One thing I have seen is it only takes a smidgeon of dust on the fan blades and the cooling all goes to pot. Things are not helped by the restrictive design of the fan shrouds. There have been times where I've been sorely tempted to run the things without them. I blow mine out every two to three weeks or so.

 

Oh well, you pays your money etc.

 

I will look into using Osram. Interestingly enough I've now got 2 3000s with them in, so we shall see how they fare against the Phillips.

 

All the best

Timmeh

[bigclive]

Although they're quite expensive to buy, thermal imaging cameras are worth their weight in gold. You can look for any thermal irregularities in an entire distro and dimmer area in seconds, and scan a gantry or rig for overheating connectors. Usually Soca that hasn't been mated correctly at some point in time and has burnt pins.

 

The top patch-bay of some dimmer racks looks particularly impressive through a thermal camera. And I don't mean that in a good way.