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  1. #1

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    Lots of enlarger bulbs blowing....why?

    Hi,

    I started using my used devere 10x8 recently when two bulbs blew. There was a little flash ( which I could see from the small amount of light spilling from around the carrier onto the wall) and the two right side LEDs went out, showing that those two bulbs had gone. I inspected them and they had blown. I replaced them and within a few prints the left two bulbs went. This time there was no flash, the light source just dimmed and the LEDs went out. I have replaceed these two so there are now 4 new bulbs in the head.

    Being used to smaller enlargers with less bulbs and having only one bulb go in 3 years, can you help on the following:

    I once heard that all bulbs should be replaced when one fails. Is this true and if so, why?

    Could it be that there was some form of surge which blew a bulb in a sudden way (flash) taking another with it immediately due to an increase in load and damaging the other two, which then shortly after gave up the ghost? (I hope so)

    Could there be a more serious problem? (I hope not)

    I have made a few prints and all seems well for now, but heck, the bulbs cost a fortune and if I have a bulb eating enlarger it could hurt a lot.

    Thanks

    Tom

  2. #2

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    Bulbs have a certain life. If you change them all at the same time then it's reasonable to expect them to die more or less at the same time. Obviously it won't be 100% exactly the same time but within a window.

    The other issue is bulbs age and change colour. If you're printing colour then having a mix of old/new bulbs might cause problems.

    I'm guessing this is a new to you enlarger? The bulbs could have gotten jostled in the move. They may just be old. When I got my smaller Durst the bulbs died not long after it got home. The replacement bulbs have lasted since then.

  3. #3
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    Not familiar with that enlarger, but if it has a voltage regulator of some description, you may want to check the voltage at the lamp sockets to make sure it is not feeding them excess voltage.

    If they are halogen (you probably know this already but it's worth repeating for anyone that doesn't) do not touch the lamps with your bare fingers: the oil from your skin will cause hot-spots that will cause the lamps to fail prematurely.

    Thinking about it, it is possible each pair of lamps are wired in series, in which case only one of a pair may have actually died and that one of each pair is still OK.

    My best guess is that Nick has hit the nail on the head and you will have a couple of years wait for another surprise...

    Cheers, Bob.

  4. #4

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    Two bulbs were of one brand and two of another, so they probably were not of the same age, but may have taken a few knocks I suppose. They blew in their respective pairs. It is stabalised and I will definitely check the voltage. One bloke I spoke to said that if oldish bulbs have sat idle for a while (this head has been in storage for 18 plus months) they tend to blow soon after being used again. May not be true, but worth a thought (cant see the mechanism tho)

    I printy mono only so no real colour balance issues.

    Thanks
    Tom

  5. #5
    Bob Carnie's Avatar
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    hi Tom

    I have run into this problem before , operated a lisle camera with I believe 16 bulbs, they seemed to blow in pairs and around the same time, once you replace with new they will last for a long time , you may unfortunately need to replace all and continue with new.

  6. #6
    Bob Carnie's Avatar
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    Tom

    sorry , didn't mention this, when replacing bulbs make sure you wear cotton gloves. the oil from your fingers is not good for longevity on these types of bulbs.

  7. #7
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    If there is a chance that the bulbs may have been touched by someone, they should be cleaned. A cotton ball with denatured alcohol will remove any residue of noseoil from the surfaces. We had a customer who learned this the hard way on his work lamps. He complained bitterly about the cost and reliability of replacement bulbs until someone asked him if he had touched the bulbs or read the included instructions.

  8. #8

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    A couple more thoughts about light bulb failures.

    In general, heat will reduce bulb reliability and a multi-bulb head will tend to run hotter than a single bulb head. Check to make sure you have good air circulation around the head and make sure any cooling vents are not obstructed.

    Voltage spikes can cause catastrophic light bulb filament failure. High voltage (that exceeds the bulb's voltage rating) is also an enemy of filament reliability. Your line voltage may be too high and "dirty" as well. You can ask the electric power company to put a voltage monitor on the electrical service to your house.
    Tom Hoskinson
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    Everything is analog - even digital :D

  9. #9

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    About touching the bulbs, I always assumed that this applied to the bulb itself rather than the reflector cone (which I touched) I took care not to touch the glass bubble around teh filament of course. Should one avoid touching the relector?

    Tom

  10. #10
    Bob F.'s Avatar
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    Quote Originally Posted by Tom Stanworth
    About touching the bulbs, I always assumed that this applied to the bulb itself rather than the reflector cone (which I touched) I took care not to touch the glass bubble around teh filament of course. Should one avoid touching the relector?

    Tom
    Good point....


    I would assume that as long as it is not a sealed unit (where the reflector is part of the lamp itself as opposed to something that simply surrounds the actual lamp) touching the refector would be OK. Having said that, I would be inclined not to risk it as it is going to get very hot too.

    Bob.

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