Timer for LPL 4550XLG Enlarger

Discussion in 'Darkroom Equipment' started by rick durbin, Oct 11, 2006.

  1. rick durbin

    rick durbin Member

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    I recently bought a 4550XGL enlarger which uses a 250 W bulb. I've tried to use a GraLab model 450 timer with it, but each of the two new units I've gotten failed some of the time to switch off the light. However, the timers (rated for a 600 W load) work perfectly when tested with a regular 100 W bulb. Any ideas what the problem is? If it's the timer, can you suggest one that you know works. Thanks. Rick Durbin
     
  2. david b

    david b Member

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    I am using a Saunders ET-500 timer without any issue.
     
  3. ann

    ann Subscriber

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    we use a beseler 8187 with ours. we also use 1 250w 82v bulb EVW with everyone with no problems.
     
  4. skillian

    skillian Subscriber

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    I have the same enlarger with a foot switch to turn it on and off and a metronome to count down the seconds. Leaves my eyes and hands free to burn and dodge.
     
  5. galyons

    galyons Member

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    Rick, the bulb is 250W, but 82 volts. The bulb is powered by the transformer which steps down the voltage. The issue may be in the transformer, not the timer. The timer is just providing a time controlled relay to turn power off and on to the transformer.

    Now, my opinion on a timer, get a RH Designs f-stop timer. IMHO, the best tool for fully understanding the relationship between all of the expsoure variables and the image produced.
    Cheers,
    Geary

     
  6. Donald Miller

    Donald Miller Member

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    I use a Gralab 550 with my 4550 XLG. While the Fstop timer is a fine piece of equipment, a person can do Fstop timing with a conventional timer.

    I use the same timer to control my 1000 watt point light source lamp. In that case I use the timer to control a relay coil to switch the voltage into the lamp.

    The amperage on a Saunders at 82 volt 250 watt is 3.04 amps. The equivalent of 600 watts at 115 volts is 5.21 amps so the switching relay in the timer you mentioned is being operated within the design parameters.

    Are these new timers that are failing? If so it may be that you have a current leak to ground and that would increase the amperage beyond the lamp current requirements. It would be possible to check for this by taking each of the transformer taps to ground with a ohm meter set on the 1000 ohms scale (unit obviously disconnected from it's power supply). While it is true that the transformer is reducing voltage, it still remains that secondary load on the transformer will affect the primary input amperage.
     
  7. Jeffrey A. Steinberg

    Jeffrey A. Steinberg Member

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    I have a kearsarge (model 300?) timer that works great with it. It is a nice digital timer. Not sure if they still make it.

    --Jeffrey
     
  8. jp80874

    jp80874 Subscriber

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    Rick,

    I used the same 4550XLG-250w bulb-GraLab 450 for about a year and a half without problem before I moved up to 8x10. The units work together so I would pursue a componet malfunction such as mentioned. It is all still set up if there is anything you want to compare or try, just send me a PM. It simply hasn't been turned on for about 15 months.

    John Powers
     
  9. RH Designs

    RH Designs Advertiser Advertiser

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    I don't know the Gralab 450 very well but if it uses solid-state relays instead of electromechanical ones then the likely cause is leakage in the relay. The LPL 4550 uses a relay built into the transformer, and it requires very little power to operate it. Solid-state relays can leak sufficient current to keep that relay energised once it has closed - this means your timer can switch the light on normally but does not switch it off again because the leakage current is keeping the relay closed. That is an inherent "feature" of solid state relays and the reason we went back to mechanical ones, after briefly using them in our StopClock Professional and Analyser Pro. Both of these products will work fine with your enlarger.
     
  10. Chan Tran

    Chan Tran Member

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    If the problem is like what Richard said then you have a few choices.
    1. Buy a different timer with mechanical relay.
    2. Modify the Gralab 450 to have mechanical relay.
    3. Add a light load in parallel with the enlarger to drain the leakage current in the off state. To test if this would work. Connect an extension cord to the timer outlet with 2 outlets at the other end. Plug the enlarger in one of the outlets and plug a small lamp into the other. 10W lamp or so would be fine. Up to 100W lamp should be no problem. If the timer now works correctly then you need to replace the lamp with something that doesn't produce light when power up. I can't think of any good thing to do this except a plain resitor but that would require some electrical work and is not very good for some one who doesn't have the experience.
     
  11. nolindan

    nolindan Member

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    Further question: Does the enlarger ever turn on without being first turned on
    by the timer?

    There are two scenarios:

    1) The timer's contacts are being 'welded' shut by the inrush current
    of the enlarger. If the timer is controlling a relay in the enlarger's
    power supply this is probably not the cause. However, if the timer
    is controlling the lamp current directly then contact welding may
    be the culprit. Does the enlarger turn off if you give the timer a
    good whack?

    2) More likely: The timer's output relay may have a snubber circuit across the contacts [or SSR output triac] to prevent arcing with
    cold-light heads and this snubber circuit passes enough current to
    activate the enlarger's power supply.

    A quick fix is to put a small resistive load at the timer output so the
    timer turns on both the load and the enlarger. Try a 7/15 watt light
    bulb for a test - plug an outlet strip into the timer and plug the light
    bulb and enlarger into the strip - and see if this fixes the problem.

    If solves the problem then putting the light bulb in a black box would
    be the easiest solution. A 1 watt 22K resistor wired accross the
    enlarger's relay coil/SSR LED would be a more permanent fix.
     
  12. rick durbin

    rick durbin Member

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    Many thanks for all your answers. I tried Linden and Tran's suggestion of putting a low-wattage bulb in parallel with the enlarger. The timer then worked OK. When I turned off the lamp, the timer often stayed on. When I turned on the light again while the timer was "stuck" on, the timer switched off. Interestingly, I borrowed a very old GraLab 450 timer that has push button-controls (and maybe an electromechanical relay). It worked perfectly. Geary, I agree with you on f-stop timing. But being rather new to enlarging I found it easier to use Stouffer's 1/3 and 1/6 step wedges. Usually, with two test strips then, I can get in the ballpark and then switch to full or half sheets. Thanks again. Rick
     
  13. galyons

    galyons Member

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    Good! It sounds as if you can print, which is most important. When I had my Omega DV2 with coldlight head I had timer issues and it was most frustrating to sort out!

    Print away!! If you want to try out f-stop timing, IIRC, there are several spreadsheet programs available to do the conversions, Palm programs, and programmable calculators, as well. But they will all be a PITA until you get equipment designed to handle the math and timing interconnected for you. (Just my plug for the RH Designs products, as a happy consumer, only!)

    Cheers,
    Geary
     
  14. LazyHammock

    LazyHammock Member

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    Sorry for your troubles Rick. I have been experiencing the same issues with a gralab 450 and an LPL 6700. It has been driving me nuts, particularly as I waste paper when the enlarger lamp spontaneously turns on. After reading this thread today I ordered an LPL timer, hopefully that will do the trick. thanks to everyone for their useful suggestions.
    Nick
     
  15. Chan Tran

    Chan Tran Member

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    So what are you going to do with the Gralab 450? I can use one for my Beseler 45 MX.
     
  16. rick durbin

    rick durbin Member

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    Sorry Tran but the infamous timer has already found another home.