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replacing a transformer

Discussion in 'General Electronics Discussion' started by elsquirrel, Dec 8, 2010.

  1. elsquirrel

    elsquirrel

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    Dec 8, 2010
    I've had an ensoniq dp/4 effects processor sitting unused for a while because it is has a US voltage transformer inside (120v), and being in Australia they only way I can use it is with a step-down transformer or changing the power supply. I'm investigating the later, and am not sure if it can be done. Ensoniq are now defunct and I also tried to contact the original manufacturer of the transformers but have yet to receive a reply.

    My question is this: Is it possible to determine the specifications for a replacement transformer if I'm not able to find any technical information at all? I'm really not that experienced with electronics though I'd like to learn and would like to avoid using a step-down transformer if all possible. (my concern with the step-down is the 50hz/60hz discrepancy).http://sound.westhost.com/articles/50-60hz.htm#s40

    Just for completeness:
    The green wires (the primary side?) are one which clips to the front panel, the on switch I think, and the other runs to a secondary power board, which then connects to a line filter at the rear of the unit. There are 9 secondary wires on one clip.
    [​IMG] [​IMG]

    I also have the service manual, though I couldn't find anything obvious that would help. (Though I may not know what I need to look for).


    Would there be some way to run a voltage through the transformer to analyse the secondary voltages maybe? What are the chances of finding something like this stock or easily modifiable? I noticed a manufacturer not far from my who make custom transformers, though I have no idea how expensive it would be.

    Any help or ideas at all would be appreciated. Thanks!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Green wires for mains primary! -- if that's right, it's a real trap.

    If the service manual has a circuit diagram, can you scan it and post it for us to take a look at?
     
  3. elsquirrel

    elsquirrel

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    Dec 8, 2010
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    That is very helpful. I would suggest that the secondary windings are something like 18V CT 2.5A and 36V CT 1A.

    That's just a guess though, and is based on the voltage readings given on page 4 and the fuse ratings on page 3, and on likely secondary voltages.

    The 18VCT winding seems to be used for logic power supply, generating +/- 5V (although what -5V is used for I don't know)

    The 36V CT winding appears to be for a +/- 15V supply, and that seems pretty normal for a low power analog device (I would expect higher voltages and a higher current rating if it contained a hefty power amplifier).

    To determine if I am in the ballpark, you would have to measure the resistance of the secondary windings and see if there are two groups of three wires that have some sort of continuity, and one pair (the primary winding).

    Can you photograph the top and bottom of the boards.

    It would also be nice to know if the serial number is between 10000 and 13074, or it is 13075 or greater.
     
  5. elsquirrel

    elsquirrel

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    Dec 8, 2010
    Here are some not so great shots I already have. I can take some clearer/larger ones tomorrow.The serial number on the case is: 20216, though on the main board it's 09712. So maybe the main the board was changed at some point. At any rate, the other parts (secondary board, line filter, etc. are the parts for serial numbers above 13074.

    The transformer when it was in: (the sticker is all the information on the transformer. It blew off like a leaf when I opened the box. :) )

    [​IMG]

    Main Board
    [​IMG]

    Transformer secondary PCB
    [​IMG]
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    OK, try to take the photos without a flash, and for the larger board, the power supply connection and a small area around it would be good. The important thing is that we be able to read markings on the board.

    To ensure that the photos are sharp, you may need to be somewhere with a lot of light, or use a tripod. If in doubt, take one with the flash too.

    The voltage ratings on those capacitors would also be nice to know.
     
  7. elsquirrel

    elsquirrel

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    Dec 8, 2010
    Hi,

    Haven't had a camera to take photos yet. Will try tomorrow.
    I did, however, get a chance to run the unit using a step down. Well, it has run ok so far, no obvious signs of distress. It does make an annoying humming/buzzing though.

    I spoke to a transformer manufacturer and they said that could take the transformer and make a replica 'starting at $150'. Could be costly, but if the 120v transformer is buzzing and will die a premature death, might be the better option in the long run.

    Do you think by figuring the output voltages myself there is any stock transformer that would work?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Yeah, a humming/buzzing transformer is on of the hazards of operating a 60Hz transformer at 50Hz.

    Another other problem is overheating. If the load on the transformer is light, this may not be a problem. If the transformer gets much more than warm to the touch after being operated for (say) an hour, then I'd exercise some caution.

    It's probably an expensive solution, but also possibly cheap compared to the piece of equipment (?). You can probably be reasonably assured that the manufacturer will do a good job.

    If you're comfortable with a multimeter, it would be useful if you can measure the voltage on the secondaries of the transformer whilst the equipment is operating.

    This could be done from the "transformer board" but remember that the mains (admittedly now only 120V -- but possibly not isolated) is also present on this board.
     
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