Beseler 23c Dual Dichro power supply troubleshooting

Discussion in 'Enlarging' started by skucera, Dec 4, 2016.

  1. skucera

    skucera Member

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    I've picked up a Beseler 23c with a Dual Dichro head, and when I plugged in the power supply to the head and turned it on, it turned on for about 5 seconds and then turned off. The fuse and the halogen bulb appear to both be OK, so I'm a little puzzled. Does anyone know where I can get troubleshooting procedures or repair manuals for this head and power supply?

    Any help is appreciated, and I apologize if I've overlooked an obvious thread. I've been Googling for answers, and I haven't found a lot of answers, hence my asking here as my maiden post on APUG.

    Thanks,
    Scott
     
  2. Leigh B

    Leigh B Member

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    Is the fuse the proper size (ampere rang) and type?
    It's not unusual to find fuses rated far above the proper value, installed by the previous owner when the right fuse blew.

    A very common problem in power supplies is bad filter capacitors.
    This will usually cause the fuse to blow if it's of the proper rating.

    Is the failure scenario repeatable, or is it now off and won't turn on?

    - Leigh
     
  3. AgX

    AgX Member

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    (What Leigh likely wanted to say: )
    If the fuse is a overrated the capacitator itself may have blown, the apparatus would not light again, but lamp and fuse look fine.

    Of course with an overated fuse other parts might have blown.

    Switch on the apparatus, check the powerline for being broken or of bad contact. Switch off, then pull the cable off the mains, check lamp and fuse, and its rating. If both are not blown, check lamp contact (though it is unlikely to go bad abruptly). Switch on again and see for the lamp. If no result, switch off and pull cable again, open the casing further and have a look at the electronics. Sometime one can see blown or smoldered parts. If everything looks fine it is time to consult a specialist...
     
    Last edited: Dec 5, 2016
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    skucera

    skucera Member

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    Ah, that points out another need... I don't have the user manuals for the enlarger or this dichro head. Anyone know where I can find some, perhaps as PDF's? The back label on the power supply clearly states that it should be a 5 amp fuse, but the fuse actually in the holder is a 3 amp fuse. If anything, thus under-rated fuse is just overprotecting the power supply.

    The failure mode is that the master power switch turns on the color head's cooling fan. The power supply also makes a very satisfying "bungggg" sound as a large solenoid energizes inside. Keep in mind that I have the gray cable that should be plugged into the timer plugged into the timer socket (the "test" mode my dad showed me when I was all of about 12), so flipping the lamp switch on should turn the light on in "focus" mode, on steadily, but it doesn't. I've checked the light bulb with an Ohmeter, and it checks out fine. Power just isn't making it to the lamp socket. If I had a schematic I'd check the pin-outs in the funky six-pin connector to see if they were routing power at the correct voltages, but I don't know what each pin should do.


    The fuse is under-rated, but the risk is that some old electrical components in the power supply have simply failed. If I had a repair manual and some schematics, I could test the components and see what needs replacing. Given the era this power supply appears to have been designed in, it should be super easy to unsolder, replace components, and resolder. At least it won't be "lead-free" solder inside, with "lead-free" brittleness and cracked solder traces.

    I think I will open the cover, but I'm going to talk to my coworkers about it first. Although I'm not an electrical engineer, my boss and one of my coworkers are EE's and grew up in the Sixties and Seventies design epochs. :wink: (Yeah, none of us are getting any younger.)

    Thanks, guys, for your ideas. If anyone happens to have manuals for the Beseler 23c or the Dual Dichro color head, please let me know. I'd love to scan them and turn them into PDF's for personal use.

    Scott
     
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    skucera

    skucera Member

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    I just found a PDF for the Dual Dichro 23 head, and I realize that there were two different power supplies for this head, stabilized and unstabilized. I've got the more expensive stabilized power supply. :smile: Now if I can only find some schematics or repair manuals....

    Scott
     
  6. Leigh B

    Leigh B Member

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    Hi Scott,

    Can you shoot me a copy of that PDF? leigh at atwaterkent dot info

    - Leigh
     
  7. mgb74

    mgb74 Subscriber

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    skucera

    skucera Member

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    Yes, that's the manual I found, so thanks for posting the link to it.

    Scott
     
  9. mgb74

    mgb74 Subscriber

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    We can thank James Ollinger. Lots of good info on his website.
     
  10. paul ron

    paul ron Member

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    schematic fot the power supply is here. years ago a lady had a vactrol problem n managed to get it for us.

    (there was a url link here which no longer exists)
     
    Last edited: Dec 7, 2016
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    skucera

    skucera Member

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    Thank you, Paul. Now I've got something I can work with. :D

    Scott
     
  12. paul ron

    paul ron Member

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    there were a few threads on that head n power supply. just do a search?
     
  13. OP
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    skucera

    skucera Member

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    I showed the schematic to a couple of the electrical engineers at work, and they were very amused. The first comment was, "When was this designed?" The style of electronic design seemed "old fashioned," even by guys who learned their craft in the Seventies and remember how things were done when they were students. The assumption was late Sixties, but they weren't really sure. I Googled the answer, and found that it was designed in 1979, and was introduced in 1980 or 1981. Those opinions were really curious.

    Anyway, I'll open the box and look for burned components later today, after the Army Navy game. Some of the components would be very difficult to source now, so I hope it's something simple like blown caps or a cracked solder trace that I can reflow.

    Scott

    Go Navy!
     
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  15. mgb74

    mgb74 Subscriber

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    I've heard that same comment from my EE son on some other products. I suspect whomever designed this in 1979 learned their craft in the 60s.

    Personally, I'm waiting for the Cobol I learned in 1970 to come back.
     
  16. OP
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    skucera

    skucera Member

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    COBOL is quite the digression. :D I learned it in 1999 because of the supposed great opportunity to rewrite old mainframe apps for Y2K. I never earned a penny from that language.

    Alright, now that Army beat Navy for the first time in 15 years, it's time to finally get down to the basement for some electronic archeology.

    Scott
     
  17. paul ron

    paul ron Member

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    hahaha you guys are a pisser.

    let us know what parts you replace yours with so anyone looking for info can find this?
     
  18. OP
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    skucera

    skucera Member

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    I don't appear to need to replace anything. It appears that solder separated with the wire from one of the socket blades. I didn't have time to resolder it, so I'll do that in a couple of days and see if it works. Meanwhile it sits on my workbench, waiting for me to find where I put my little soldering iron.

    Scott
     
  19. Leigh B

    Leigh B Member

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    That suggests a serious problem.

    There's no way a power contact should ever get even warm to the touch, certainly not hot enough to melt solder (~370 °F).

    - Leigh
     
  20. AgX

    AgX Member

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    Well, if there was a severe contact issue between the two parts of the connector one could not exclude the temperature rising that high.
     
  21. Liminal

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    I also have two Beseler model color heads (45S and Dual DichroS) with fried power supplies (in my case due to opto-isolator failure mentioned by Paul above). Given that many of these old beseler power supplies seem to be giving up the ghost -I wonder if we might be able to find a comparable modern power supply and just switch it out completely... Does anyone know the actual voltage output on the Dual DichroS and/or 45S power supply? Bulb for both is EVW, rated at 82V / 250W...

    But is that AC or DC? And what is the actual output of the power supply (probably less than 82V...)?

    Anyone have a functioning unit and a voltage meter?
     
  22. Steve Smith

    Steve Smith Member

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    82 volts is a common voltage for an enlarger bulb. It can be run from a 110v ac supply with just a diode in series.


    Steve.
     
  23. Leigh B

    Leigh B Member

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    The required AC (rms) and DC voltages are identical for a resistive load like a light bulb.

    In fact, AC voltage is defined as the value that will heat a resistor to the same temp as the DC voltage.

    - Leigh
     
  24. Leigh B

    Leigh B Member

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    There is one common, almost universal, failure mode for power supplies more than 20 years old.

    It's the electrolytic filter capacitors going bad. Sometimes they short, sometimes they open, but in either case they no longer work. If they short, they usually cause a fuse to blow, and may damage other components. Open caps usually cause no collateral damage. This problem accounts for maybe 90% of repairs to such equipment.

    For those who are electrically inclined, this can be a user fix.
    Aluminum electrolytic capacitors are usually in aluminum cylindrical cans, one to three inches in diameter and maybe three inches tall. Hopefully they're the type with screw terminals on top, and wires with lugs bolted in place. For these you just unscrew the lugs (NOTE THE POLARITY + or -). Remove the old cap, install the new one and connect the wires.

    The other common type has solder terminals at one end with wires attached. These must be moved to the new cap.

    Aluminum electrolytics are also made in cylindrical packages with wire leads (one at each end or both at one end).
    These have a polarity indicator on the plastic wrapper, probably a plus sign for caps of that age. Modern ones have a minus sign.

    When replacing capacitors, you must always match the voltage (DCV) and the capacitance (microfarads aka MFD).
    Modern electrolytics are readily available and not expensive. Good vendors include Mouser, Digi-Key, and Newark (see below).
    Good brands include AVX (nee Aerovox), Toshiba, Panasonic, Sprague, Cornell-Dubilier (CDE), United Chemi-Con (UCC), and Vishay.

    Websites:
    Dead Link Removed
    http://www.digikey.com/products/en/...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
    http://www.newark.com/aluminium-electrolytic-capacitors

    - Leigh
     
    Last edited: Dec 14, 2016
  25. ic-racer

    ic-racer Member

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    Since the D5500 power supply also drives the closed-loop filter motors, I rebuilt them from scratch. Your power supplies might also be rebuildable. To power the lamp, frequently the supply waveform is broken up by the TRIAC to pulse the lamp with the appropriate voltage 82v in my case, sensed by a 'true RMS' chip.
    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Dec 14, 2016
  26. ic-racer

    ic-racer Member

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    If they were photographers, the same comments might be applied to your mechanical film camera if you have one.
     
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