Mac 250 dim light output

[knightdan65]

Hi,

 

Recently bought two second hand Mac 250 kryptons. They’re in fair condition for what I paid, however one is significantly dimmer than the other. Before I buy a fresh lamp for it, does this sound like something More serious than a bulb? Or maybe the internals just need a good clean? If anyone could shine some light (pun emphatically intended) on this I’d be most grateful.

 

Dan

[indyld]

Put the good lamp in the dim unit (or vice versa). It could be the lamp or something else, but swapping them will tell you where to look next.

[DrV]

It might simply be out of alignment. Adjusting the position of the lamp (known as 'peaking' it) is important. Instructions are in the manual but it just involves rotating the 3 hex head adjusting screws on the back of the lamp base while pointing the fixture at a plain surface. Turn them individually half - one turn at a time to centre the beam and then turn all three together either in or out to get the maximum brightness. One way you'll find tends towards a bright spot in the middle of the field, the other way just makes it get dimmer. The optimum is as bright as you can get without causing the spot.

[knightdan65]

Thanks! Will try this first

[knightdan65]

No joy with the peaking unfortunately. I’ve ordered a new lamp, but in my mind lamps either work or they don’t - is it possible for a lamp to dim over time?

[timsabre]

Yes, discharge lamps become dimmer and often change colour as they age.

You will need to do the adjustment again when you put the new lamp in. That would have been my first suggestion too having battled with Mac250 Kryptons in a local venue which have vastly differing brightnesses.

 

[DrV]

No joy with the peaking unfortunately. I’ve ordered a new lamp, but in my mind lamps either work or they don’t - is it possible for a lamp to dim over time?

Yes they do. If you look at the glass (actually quartz) it should be completely clear, or at least nearly so. As they age the quartz becomes de-vitrified and starts to appear frosted. Eventually the de-vitrification becomes severe and the envelope becomes weak enough that it can't withstand the high pressure inside so it bursts. This is a Bad Thing which is why you have a lamp hour counter in the fixture. You should replace the lamp when its specified life has elapsed to minimise the chance of it bursting and spraying the inside of the fixture with hot shards of quartz!

Dave

[knightdan65]

What would I do without you guys?