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Vintage Mixing Console needs Power Supply HELP?

Discussion in 'Vintage Analog Gear' started by stustustudio, May 2, 2012.

  1. stustustudio

    stustustudio Active Member

    i had an 80's Walker Mixing Console givin to me without a power supply here are some photos - any leads/help? mixer-002web.jpg mixweb1.jpg mixxer-005web.jpg
     
  2. stustustudio

    stustustudio Active Member

    looks like there are 4 wires soldered to connector that have +15V/-15V/G/P written in pencil beside them and there is a 3A written on the board
     
  3. dvdhawk

    dvdhawk Well-Known Member

    Not an answer, but another observation - the multi-pin plug has been replaced with a cheapo 5-pin DIN plug somewhere along the way. I don't think the DIN plug was designed to handle much amperage. Replace that while you're at it.
     
  4. djmukilteo

    djmukilteo Well-Known Member

    The "P" could stand for "Phantom" power? Does the board have a +48V phantom power switch on each channel strip?

    G=ground
    +15VDC/-15VDC
    P=+48VDC phantom power for condenser mics.

    Unless you can find that particular brand somewhere, you would need to build one or buy one off the shelf.
    You need one supply module +/-15VDC and that 3A figure might be the maximum current needed to power the board up at full load, so 3A output current.
    If you can find a bench top linear power supplies that will give you dual channels for the +/-15VDC@3A, that would power up the mixing consoleand a good way to test the mixer out.
    Those types of power supplies have short circuit proof features for testing stuff so it would be a good way to go.
    You'll then need one supply module +48VDC with enough current to power 24 microphones.
    The 48VDC Phantom power can be a separate supply (common the grounds of course) and I would think 0.5A-1.0A is enough current to power 24 mics simultaneously. If you need that. If your just using instruments and dynamic mics and don't care about using the phantom power then you can ignore that for now.
    DIN connectors are pretty crappy poor connectors and easily fail to make connection very unreliable... so I have to agree with DVDHawk to replace it. I would just install a barrier terminal strip with screw terminals which will make it easy to hookup and test.
    I'd start with just the +/-15VDC power supply first and test everything....
    If you don't have the schematics you should try to find those....you might need it if it doesn't work.

    You should be able to put a meter on that "P" lead (with no power hooked up) and press a phantom switch and see if you get some resistance reading or continuity....that would be one way to see if that "P" is the phantom power line.
    Hope that helps
     
  5. stustustudio

    stustustudio Active Member

    pcb.jpg thanks you MUCH for responding djmukilteo looks like whoever wrote the +15/-15/G/P on board must have been the one who replaced the switch to DIN. Not sure if its correct though so i made a chart of what i actually see them connected to.
     
  6. stustustudio

    stustustudio Active Member

    as well there are no phantom power switches on any channels just one on/off switch right at the DIN (mentioned in pic above) that says Phantom Power ON and a led light.
     
  7. djmukilteo

    djmukilteo Well-Known Member

    That would be what you need then.
    +/-15VDC supply and then a +48VDC Phantom power supply.
    I would replace the DIN and still use a protected test power supply first and hook it up to +/-15VDC.
    That way you can check the mixer. There could be some bad electrolytic caps in there so look at them and see if any of them show any leakage and look at the tops to see if any have any bulge.
    You can always get a phantom power supply later if you need it.
    The +/-15VDC supplies power to all of the circuitry for the mixer itself.
     
  8. stustustudio

    stustustudio Active Member

    Also the same person who wrote 3A (black marker) on board also wrote "-15" on what looks like a fuse that comes from the 1-yellow line and respectively the other fuse labeled "+15" comes from the 2-gray line (both which correspond to a factory ,"-" and "+", label on board). this makes me think that these two lines are the -15V/+15V lines. unfortunately the guy who wrote in pencil/pen and probably installed the DIN had it wrong, and hopefully corrected it before attempting to turn on. (pencil/pen guy wrote -15 on 1-yellow, which seems right, but +15 on the 4-yellow wire?) - here's a pic of the fuses mixer-006.jpg
     
  9. djmukilteo

    djmukilteo Well-Known Member

    Well the fuses will be the +15 and -15 power connections and that's all you need to power up the mixer.
    What value fuses are in there? That might help determine power requirements.
    Is there any wattage listings anywhere on anything?
    So did someone try to make a power supply for this mixer or is that the original board?
    Are those automotive fuse holders something added by someone after the fact?
    See this is why it would be handy to have schematics!
    Your photos seem to only show small areas of the bigger picture.
    It might be more helpful if you take a full photo.
     
  10. stustustudio

    stustustudio Active Member

    your right those automotive looking fuses have been added after the fact - they are F1.5A250V each. and clearly the guy who wrote "3A" on the board in marker installed these fuses. here are some more pics to show how i got it. the board is modular and i was told by the person i got this board from that the two spaces were blank strips which he has somewhere, it makes sense because the "ports" (where these modular strips fit into) aren't even screwed into the board where the blanks are - like all the other strips do. there are no wattage markings anywhere, everything here is original (except the DIN and the automotive fuses) the only time it says +/-15 is in marker on fuses and in pen by DIN wires, as i said they don't match. ARghhh.
    mmixxer-004web.jpg mmixxer-005wweb.jpg mmixxer-007wweb.jpg
    I don't see an ON/OFF switch anywhere just the Phantom Power ON top right of mixer where DIN is on back, could the external power supply (that's missing) been the only ON/OFF switch?
     
  11. djmukilteo

    djmukilteo Well-Known Member

    So only label is Walker 2440? (which looks like a 24 channels/4 bus 24X4).
    Is there any other labels or markings on the mixer case on the back or on the boards inside?
    You should take a close up of the channel boards showing the components and part numbers.
    You could then find the datasheets and then verify the supply rail voltage for sure.

    Someone must have figured out the +/-15VDC and that is the standard opamp supply.
    1.5A per rail makes sense as that total of 3A would be the right rating for a dual output supply.

    Maybe it never had phantom power if there are no individual switches to engage that per channel. Does it look like someone tried to add that to the mixer?
    That would be sort of unusual having them either "all on" or "all off".

    But like I said you don't need phantom power to test out the mixer.
    Just use a dynamic mic or signal generator to test it with a dual output bench supply. If it all works great you could build a separate power supply box and replace the wire harness at the back or just continue to use the bench supply.
    Looks like a project for sure...luckily it was free. It's 30 years old so who knows how much of it actually still works.
    The only way your going to figure that out is to get ahold of a +/-15VDC bench supply and test it out.

    A lot of those older mixers used external power supplies which were rack mounted or sat on the floor next to the mixer and that had the power switch on it to turn the mixer on. Then there was just a cable going to the mixer from the power supply box with the different voltages. There was always this idea that a separate power supply box located away from the mixer created less power supply hum and noise getting into the mixer itself. Many times the wire harness between the two was shielded to help keep any noise out as well.
    So that's why the mixer itself doesn't have any power switch.
     
  12. stustustudio

    stustustudio Active Member

    it definately has a factory phantom power on switch at the top right of the board you can see it in the pic above, could it maybe have an auto detect/on when you plug in phantom powered mics? from what i've found already, Walker later Pulsar were made out of akron ohio in the late 70's into mid 80's and boards like this were sold to studios (no-one liked them for live because they weren't that sturdy construction-wise) in the 5-11 thousand range. no luck on schematics though. Wish i could borrow a PSU to try and see if she lights up, then buy if it does - would the 4-yellow (above chart) be the Ground?
     
  13. stustustudio

    stustustudio Active Member

    just called the local electronics store and they say they have a linear +/-15vdc power supply but he does know if its dual or not, and it doesn't have a ground, just two outs
    -15vdc and +15vdc - no three prong plug - for $30! sounds cheap - maybe i could put a three prong on it then run that through to the ground (4-yellow) on the board?
     
  14. djmukilteo

    djmukilteo Well-Known Member

    You can use a meter and trace that out and verify it is the ground rail. Sometimes drawing out a schematic will help you see whats going on too.
    That yellow wire was labeled G in the photo which would be ground and you said it goes to the negative side of the big cap...so that would be a good guess.

    Here's a typical mic preamp circuit with +48V phantom power being switched in or out to a specific preamp channel.

    http://www.thatcorp.com/datashts/dn140.pdf

    That was the usual way to provide phantom power to a condenser mic plugged into the preamp.
    This circuit uses +/-18VDC to power the preamp (V+/V-) but 15VDC was just as typical for supply rails.
    Like I said the phantom power isn't important at this point.
    Just find a +/-15V dual output power supply and see if the mixer and preamps work.
    You can always buy a separate phantom power pak that connects directly to a condenser mic if that's what your using.
    Any dynamic mic like a SM57/58 will work just fine without the need for the 48V.
     
  15. stustustudio

    stustustudio Active Member

    okay - all this is starting to make sense - only one last request and again thank you so much for your help, i really appreciate it, if the +/-15V power supply is two prong can i modify it - put a three prong plug on it and run the ground through to the board?
     
  16. djmukilteo

    djmukilteo Well-Known Member

    It needs to be able to provide +15 AND -15 at least 1A with a common ground.
    A three prong plug if your talking about the AC cord going into the power supply has nothing to do with the DC output.
     
  17. djmukilteo

    djmukilteo Well-Known Member

    Here's a schematic of a dual polarity power supply like what you need

    Dual Polarity Power Supply
     
  18. stustustudio

    stustustudio Active Member

    it only has two outs a -15VDC and a +15VDC at 3A, so i connect those two VDC's to the corresponding terminals on the mixer, but where is the ground gonna come from? the store says the power supply has two pronged plug.
     
  19. djmukilteo

    djmukilteo Well-Known Member

    Here's another one:

    http://orca.st.usm.edu/~jmneal/dual_psu/
     
  20. djmukilteo

    djmukilteo Well-Known Member

    That one sounds like it's not dual so it won't work.
     

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