Does my bulb need to go?

[Rockers]

Our MSP 3140 takes ages to expose screens coated with Ulano QLT emulsion. I think we are at 150LTU for a roller frames 102 mesh coated 1/2. Even on the Ulano orange we never got below 65 LTU. Sericol Dirasol 916 takes at least 350-400 LTU. I used to get away with 260 LTU but somehow that has changed. The bulb is maybe 1-1 1/2 years old.
I`m just wondering does the live of the bulb rapidly decrease in areas of high humidity? I had a look at the bulb today and it jas this grayish layer around the glas on the inside, just a few spots are 100% clear. Maybe a sign to change it?

[tpitman]

The number of light units shouldn't change to get the same exposure. The amount of time it takes to achieve the same number of light units might change as the bulb ages, which is what the light integrator is for -- to adjust the time as necessary to achieve the correct number of light units. Increasing the number of light units should be overexposing your emulsion, if your calculations were correct in your initial tests, as well as increasing the time it takes to expose.

[Screened Gear]

The number of light units shouldn't change to get the same exposure. The amount of time it takes to achieve the same number of light units might change as the bulb ages, which is what the light integrator is for -- to adjust the time as necessary to achieve the correct number of light units. Increasing the number of light units should be overexposing your emulsion, if your calculations were correct in your initial tests, as well as increasing the time it takes to expose.

That is a great point.

My exposure unit has only adjusted by a few seconds in 2 years. I expose around 30 to 45 screens a week on average. I know the life of a MH bulb has more to do with strikes then it does run time so that maybe part of it. I can't imagine humidity would effect it much since its a closed bulb.

[tonypep]

Humidity? Never heard of that but; after 18 months perhaps. If you have the $ get a new one and keep the original as a spare. That graying is a tell.

[RonH]

Similar to any style light bulb, the life of these lamps varies depending on many factors.  It could last you 6 months or I have seen them go past two years.  If your exposures have changed that much with the same lamp that is currently in the unit, I would suggest replacing the lamp.  While replacing the lamp, check the transformer tap settings to be sure your unit is matched to the voltage that is coming into your MSP3140.  If the voltage in your area has changed since you last checked it, this will affect the lamp output.  I would also take this opportunity to clean the reflector and the reflector glass. 

Ron Hopkins
NuArc Sales Manager
M&R Sales and Service Co.
O-770-254-1584
C-847-997-2487

[mk162]

I think that happened with our 40-1k, I think the bulbs were getting weaker from the manufacturer, or some bad ones were made.  I always ordered ours from M&R and it seemed over the years they just weren't as good.  It happens.  I don't blame M&R, they don't make them, and frankly it's an older unit, I can understand switching vendors because the bulbs aren't made anymore.

I would get a new bulb from M&R and see if that solves your problems.

[Sbrem]

metal halide bulbs age, and therefore take longer to make an exposure; let it go long enough, and it will get pretty bad. We use a Violux 5000S, and change the bulb every 9 - 12 months, and keep the old one as an emergency backup. Actually, I used to notice that the light seemed a different color, like it got greener...

Steve

[Rockers]

Similar to any style light bulb, the life of these lamps varies depending on many factors.  It could last you 6 months or I have seen them go past two years.  If your exposures have changed that much with the same lamp that is currently in the unit, I would suggest replacing the lamp.  While replacing the lamp, check the transformer tap settings to be sure your unit is matched to the voltage that is coming into your MSP3140.  If the voltage in your area has changed since you last checked it, this will affect the lamp output.  I would also take this opportunity to clean the reflector and the reflector glass. 

Ron Hopkins
NuArc Sales Manager
M&R Sales and Service Co.
O-770-254-1584
C-847-997-2487

Done all of the above earlier today, apart from changing the bulb. Will place an order tomorrow with the HongKong office. Cheers.