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  1. #1
    ic-racer's Avatar
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    D5500 Power Supply--Complete Rebuild From Scratch

    I have been planning on doing this for some time but finally am getting around to it.

    Project: Completely rebuild a D5500 power supply module.

    History: I have 4 power modules that work with varying degrees of competency. One blows bulbs occasionally and another works except the light won't go on. Another works but the filters 'hunt' a little too much.

    The service manual recommends "Power Supply Board Replacement" for all the above conditions. F-point used to carry Omega parts and had a brand new power supply board listed for $200 USD for many years. I was going to buy it as a spare but it turns out they got out of the parts business. (I sure hope that power supply did not wind up in the trash. :o)

    There really are not that many components on the power supply board and it looks like one could just replace all components to re-manufacture a brand-new board.

    Component Selection:

    Even though D5500s were available new into the late 90s, it appears they were assembled from batches of components that were acquired when the enlarger was first introduced in the mid 80s. So, most all of the semiconductors in the power supply are outdated.

    I used the D5500 shop manual parts list and the schematic, along with detailed visual analysis of each part. Paying attention to matching operating characteristic and mounting hole pitch and component size.

    After a lot of internet searching and analyzing all the component datasheets I came up with a list of every component on the power board except the two transformers and the ribbon connectors (which I plan to leave in place). Everything else has been sourced and will be replaced.

  2. #2
    ic-racer's Avatar
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    These 4 jpgs contain a list of all the components from the D5500 power supply board with cross-reference labels from the D5500 parts list and current Mouser.com or Digikey.com part numbers.




  3. #3
    ic-racer's Avatar
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    I have 3 complete working head/controller systems and 4 power modules. I plan on re-building one of the power modules and if all goes well, to do a second one or perhaps a third also.

    The D5500 controllers have about twice as many parts, including some ePROMs that are unique to the D5500. So, a similar re-building approach for the controllers is not practical. Fortunately, I have 3 controllers that seem to be in good working condition. Since the controllers can easily be swapped from one enlarger to the next, only one working controller is needed anyway. Whereas it takes from 15 to 20 minutes to swap out the power module.

  4. #4
    ic-racer's Avatar
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    Here is a picture of a D5500 power board, ready to be re-built.


  5. #5

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    Man, you're really going about this the hard way. I would start by measuring all the voltages with reference to the schematic. quite likely you have a single or at most a few resistors or caps that have gone off value. While I admire your dedication, it's a rather simple repair that shouldn't be all that hard.

  6. #6
    L Gebhardt's Avatar
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    Quote Originally Posted by epatsellis View Post
    Man, you're really going about this the hard way. I would start by measuring all the voltages with reference to the schematic. quite likely you have a single or at most a few resistors or caps that have gone off value. While I admire your dedication, it's a rather simple repair that shouldn't be all that hard.
    Dumb question, but how do you test components that are part of a circuit? I know I can use a multimeter to measure resistance when the resistor is out of a circuit, but will it give the same reading when a resistor is in a circuit? Same with testing capacitors, diodes and other components. Or are you saying the schematic should contain test points and marked voltages?

  7. #7
    Nicholas Lindan's Avatar
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    Most likely the only failed components will be the electrolytic capacitors. Looks like they used pretty cheap ones. The other likely failure would be the Q4008 triacs. Also replace anything that looks burned or where the board has become discolored.

    I would start by limiting the replacement to these parts and see if the boards come to life.

    80's vintage semiconductors should be perfectly good. Replacing IC's, unless you have a something like a Pace desoldering station, is not a good idea as there is a very high probability of damaging the circuit board, especially true of double sided boards with plated through holes. If you must replace them then cut the legs from the body at the top of the board, heat the pin from the bottom and pull each pin from the top. Use a solder-sucker or braid to clean the holes out.

    There is an engineering adage: "Fix anything long enough and you will really break it."
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  8. #8
    Nicholas Lindan's Avatar
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    Quote Originally Posted by L Gebhardt View Post
    Dumb question, but how do you test components that are part of a circuit? I know I can use a multimeter to measure resistance when the resistor is out of a circuit, but will it give the same reading when a resistor is in a circuit? ....
    http://en.wikipedia.org/wiki/Bed_of_nails_tester
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  9. #9

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    Pretty much as nicholas stated, though I have a logic analyzer and 2 oscilloscopes on my bench as well. Well, lots more, but you get the idea. Desoldering double sided plated through holes without the proper tools, well you'd better off just dousing it in lighter fluid and save yourself the frustration.

    If it were on my bench, I'd isolate the fault, figure out which part of the circuit is responsible for that function and do a little hunting, after I replaced the electrolytics, as Nicholas suggested, you will likely find it's a simple failure of a $.10 component, at best.

    The likelyhood of the bulk foil caps failing is about zero, maybe a little less.

  10. #10

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    I'd give the connector pins a very close inspection, even to the point of resoldering every one of them. One of our cars had a digital instrument cluster, after a few years they started getting errors. Replace it or pay $1,100 for a rebuild. Well it turns out the design spec was so cheap the harness connector shells had no physical attachment to the circuit board, just the solder joints on the pins. Now how much stress does a wiring harness put on a circuit board in a car? Esp when you have to pull and twist on the cluster to wiggle your hand in behind it to remove the connectors to replace a burnt bulb. Resoldering the connectors cured all the intermittent errors in the cluster.

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