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  1. #11

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    Increasing bulb life

    It is my understanding that if you are able to reduce the voltage by even ten percent that the bulb life is greatly extended. I use a condenser enlarger and I use a constant aperture and time. I control my exposure time thru adjusting the bilbs brightness. To control the voltage I bought a lamp dimmer from Home Depot...approx. $10.00 It works very nicely. I also use one on a bulb for viewing wet prints so that the brightness of my print examination is similar to the conditions in which they will be displayed.

  2. #12

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    Quote Originally Posted by Bob F.
    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.
    Cheers, Bob.
    That one is well worth checking. It would be unusual for two bulbs to go at the same time, let alone for the same thing to happen twice. The chances are that two of your old bulbs will still work, unless there is a fairly serious electrical problem that is putting in fairly massive spikes. I don't know the enlarger so don't know how it is wired.

    David.

  3. #13
    BarryWilkinson's Avatar
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    If you know someone with an electronics background they could check/adjust the output voltage of the power supply using a 500W load. There are cheaper 24V 250W lamps around than the type used by De Vere. Simpy wire two test lamps in series to make a test load. Mount them where the heat will not cause any injury/damage.

    I believe that the De Vere power supplies 'bleed' a little current to keep the bulbs warm to reduce the start-up stress? I have a single bulb De Vere head, with the lamp on measuring the lamp voltage shows 22V, Lamp off 1.45V. There are at least two types of De Vere power supplies, Linear and switchmode. Mine is a switchmode which appears to have the 'bleed' facility. Not sure if this is applicable to the Linear supplies?

    Another possible cause is the ceramic lamp holders are burnt. They do arc when old and cause additional heat to the lamp.

    Barry

  4. #14
    BarryWilkinson's Avatar
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    I just reailised that your head is a 8x10, requiring 4 test bulbs. Not sure if these are in series or series/parallel.

    Sorry for the mistake

    Barry

  5. #15

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    two bulbs blew both times. The filaments on both had gone. I now have spent a whole day printing on the new bulbs and all seems well, touch wood.

  6. #16

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    Had a similar problem years ago. It was amazingly simple to correct, and cost NOTHING!

    I had a Beseler 67S dichro head that used the original quartz-halogen bulb for years until it died. Paid $25 for a new one that lasted only a few hours. Went back to shop to complain. They graciously replaced it gratis and then told my why BOTH had failed! Not a bad lamp, not a voltage spike (already reduced from 120 to 24V), but bad AC plug prong.

    This was years ago before polarized plugs and before three prong, grounded plugs. We dinosaurs remember the old plugs had only two identical prongs. Each was made of bent copper, slightly separated from itself so that it expanded to meet the metal in the receptacle. Over time, the bend becomes flattened and acts like a single blade. When plugged into the receptacle it makes initial contact, but occasionally the contact is momentarily broken, then immediately restored. This happens repeatedly, sometimes very quickly causing arcing in the receptacle, which you cannot see or hear. Naturally, this is detrimental to the bulb and soon burns out the filament. The solution then was to separate the bent metal of each prong of the plug, and keep them separated. This I did and the problem never occurred again. Bulbs lasted for years. The salesman at the photo store was 100% correct.

    I, too, have a DeVere, and it has solid plug prongs. If your plug prongs are folded copper that have been flattened, separate them with a small screwdriver. But since almost all electrical equipment today has either polarized plugs or three-pronged plugs, I doubt that is your problem. However, the wiring to your receptacle or the wiring from the plug could be intermittently defective. If you are getting unperceivable, split second interruptions of current to the lamp, you are shortening the life of the filament. Two things could be wrong. First, check for tightly fitting plugs, bad wiring in the receptacle, or bad wiring to or from receptacle. Frayed or cracked insulation could indicate old or damaged wiring and could be suspect. Inadequately spliced or poorly wirenut-joined wires also are suspect.

    Second, and this is a long shot, check the ground. If non-existent or insufficient in the receptacle, fix it AND run a redundant ground wire from the enlarger chassis to a nearby metal plumbing pipe, bypassing the receptacle ground.

    Barring any electrical problem in the enlarger (intermittent short or open), this could correct your problem.

    Good luck and let the rest of the world know how you solve your problem.

  7. #17

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    All appears to be well now. I disconnected all the plugs and connected again in case of a bad connection. Either this was the cure or the bulbs were old and tend to fail in pairs.

    Tom

  8. #18
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    This may be too simple but it sounded as if you were using the enlarger after buying it used? It seems that when used electrical devices are moved, the fragile elements are more apt to be stressed and fail. Even moving an electrical clothes dryer invites a failed heating element. I went through this on two different used dichro heads that had bulbs fail almost immediately after putting them into use. The replacements have continued on with normal life.

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