Power supply for vintage mixer AC 17-0-17

Discussion in 'Power Electronics' started by RARVA, May 25, 2018.

  1. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
    Hello, I'm in need of expert help.
    So I've come across a old rack mixer that I need to put to use.
    Problem is that it was part of a complete system and power came from sub woofer box as well as the signal, there was a power adapter for this back in the day to use the mixer as standalone. But not for sale anymore obviously, so I guess I will have to build my own.
    I will try to give the all the information I could find, and hope that someone can help me with this.

    The mixer: Viscount Micromix

    link to the complete system manual:
    https://www.yumpu.com/en/document/v...no-inglese-voice-system-factotum-musicyocom/5

    Schematics are in the PDF attached.

    In the back, on the power input, theres only one label AC 17-0-17 (sorry forgot to take a photo to the back side.)
    I'm guessing 17V positive -17V negative (34V AC)

    Thank you guys in advance!
     
  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    7,007
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    Close. but not positive and negative. The input is 34 Vac center-tapped. With the center-tap connected to the system ground, this yields two 17 Vac voltages that are 180 degrees out of phase. I agree that finding an exact match will be difficult, but there are other ways.

    Check F1 and F2 to see if they are 800 mA or 1800 mA (1.8 A). The schematic is not clear. A transformer with either a single center-tapped secondary or dual independent secondaries that can be combined for somewhere between 16 Vac and 19 Vac per phase will work. Mounting it in a small box with a line cord, switch, and output cable is a weekend project.

    * * * * for supplying the schematics with the question.

    ak
     
  3. bertus

    Administrator

    Apr 5, 2008
    18,350
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    Hello,

    @AnalogKid , The fuses are T 800 mA (800 mA slow blow):

    Micromix_supply.png

    Bertus
     
  4. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
  5. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    One of them has 4 wires and the other has 7, so they're not the same. Where are you located?

    Is there a label on the back of the unit that says what the input current or power is?

    ak
     
  6. thedoc8

    Active Member

    Nov 28, 2012
    54
    6
    The second one should work, as it has 17 0 17 . Just a little lean on the 5 amps. I would try, can't hurt anything. Just 3 regulators. Check tag as an log kid suggested
     
  7. thedoc8

    Active Member

    Nov 28, 2012
    54
    6
    Is that 5 amp or .5 can't see the transformer to we'll on my phone
     
  8. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
    :) above the pic was the link to the sellers product
     
  9. dendad

    Well-Known Member

    Feb 20, 2016
    1,897
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    The toroidal transformer will work ok.
    Just be sure to connect the 2 primaries in parallel the correct way for 120V, or in series, once again, the correct way, for 240V.
    If you are not sure how to do that, just ask for some help.
     
  10. Ylli

    Member

    Nov 13, 2015
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  11. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
    Hi again guys, thanks for the input!
    I live in Portugal.
    I'm still kind of confused in what type (which terms to use for searches) but I got the picture... I think.
    As long as it is somewhere between 2x16v and 2x19v or single 32v and 38v I should manage to work it out.
    Now I'm left with the question... current? 10w? 5va? what should I be looking for here?
     
  12. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    You would need a center tap transformer of minimum 30 VA.
    One side of the transformer goes to pin 1 of the connector.
    The center connection of the transformer goes to pin 2 of the connector.
    The other side of the transformer goes to pin 3 of the connector.

    (for the connections see post#3)

    Bertus
     
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  13. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
    wow 30va... I was looking at transformers around 6va... hehehe this is going to cost me more than I though! :)
    Found a UK seller with a myriad of choices... going to look at it!
     
  14. ian field

    AAC Fanatic!

    Oct 27, 2012
    6,172
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    The toroid also has less stray magnetic flux - quite handy if there's sensitive signal lines in the vicinity.
     
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  15. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
  16. ian field

    AAC Fanatic!

    Oct 27, 2012
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    If you go for the toroid - don't make shorted turns strapping it down.

    Usually a single stout bolt up through the middle. You need soft mounting washers so the surface windings don't get cramped/chaffed - the top washer needs to be backed up with a big "penny washer" to stop the padding pulling through the middle. Fill the space around the bolt with something non conductive so it doesn't go sideways if the unit is dropped.
     
  17. RARVA

    Thread Starter Member

    Jan 29, 2018
    39
    4
    Ok guys, saga is complete, end up buying:

    BREVE TUFVASSONS TTS35/Z230/17-17V
    Transformador: toroidal; 35VA; 230VAC; 17V; 17V; 1,02A; 1,02A; 0,5kg ROHS
    [​IMG]
    12€ plus transport

    Will do the follow up, but for now... THANKS for your patience!:D
     
  18. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    That one would perfectly fit the bill.

    Bertus
     
  19. ian field

    AAC Fanatic!

    Oct 27, 2012
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    That looks pretty sound.
     
  20. Ylli

    Member

    Nov 13, 2015
    321
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    Good choice. It does have two separate 17 volt windings, so will have have to connect these in series aiding. Looks like they are coded - banded red to pin 1, unbanded red and banded yellow to pin 2, and unbanded yellow to pin 3. Meter should show about 34 vac between pins 1 & 3.
     
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