In need of a Power Supply for a Alesis Multimix 8 USB (18V) (Will pay)

Discussion in 'Tech Talk - Electronic Repair Modifications DIY' started by bass_and_art, Apr 4, 2013.

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  1. bass_and_art

    bass_and_art Active Member

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    I was just given the Alesis Multimix 8 USB but my friend had accidentally thrown out the power supply with some other old electronics. As it would turn out, this is very hard to find. There are no after-market power supplies made, as far as I can tell. The specs are 18V 500 mA and here is a picture of what I need:
    Snapshot_20130404.jpg

    If anyone out there has this kind of power supply I will gladly pay what I can. I don't have a lot of money, but just let me know what sounds good to you. or if you know where I can get one that will work I would greatly appreciate being pointed in the right direction.

    quickest way to get a response for anyone who has one they can sell is to e-mail me at thomaspatton2010@yahoo.com

    Thank you for anyone who can help.
     
  2. Kurt Foster

    Kurt Foster Well-Known Member

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    did you try a search of Google? it took me less than 1 minute to find THIS.


    yhst-15436568105612_2256_4254169.gif

    POWER ADAPTER, 18*2VAC @ 1000mA, 110V
    Regular price: $45.00
    Sale price: $45.00
     
  3. McMurphy

    McMurphy Guest

    Well there you go... exactly what you need.

    On the other hand, it's no big deal to make your own power supply. All you need is a 110-24 V transformer, rated for 1.5/2 amps. In-line fuse and power switch. A bridge rectifier. A couple of large filter capacitors and an National Semiconductor, Texas Instrument, etc., 18 V regulator rated at least at 1 amp or more. And then you have a power supply costing about $25. You build it into an aluminum project box. Everything available at RadioShack.

    Frequently it's hard to find specialized connectors for these power supplies to your mixer. Sometimes it requires a modification to a 4 or 5 pin, XLR connector which are much easier to find in comparison to some of those bizarre Taiwanese connectors. 4 pin XLR's were regularly used for 12 V power supply connectors for video cameras. Pin 1, is ground and Pin 4, was 12 V of positive DC. 2 & 3 were not utilized. Sometimes you find these on other mixers with ground, +48, +15, -15.

    The only thing you have to find out is whether it required 18 V of DC or 18 V of AC? One will be the lucky and the other will take it out forever LOL. And I'm wondering how they obtained +48 for the Phantom power? So they are likely using a DC to DC up converter? So I really question that rating of 18 V? Maybe you should pick up a manual that includes a schematic? They can be helpful.

    McMurphy
     
  4. Boswell

    Boswell Moderator Well-Known Member

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    The Multimix 8 USB only needs a.c. power (at 18.5V 700mA), as the rectifiers, regulators and smoothing capacitors are built into the unit.

    If you design your mixer to take low-voltage a.c. power rather than d.c., it's easy to use voltage-multiplying techniques to get the 48V phantom power rail. The required current is only a few mA.

    The mixer unit would probably work on 18V d.c. input, but there would be no phantom power.

    PS I would snap up that power unit from Instrumental Parts while it's still in the sale and before it goes back to its normal price.
     
  5. McMurphy

    McMurphy Guest

    Yeah Boswell, I checked the specs on that mixer power supply.

    So it only requires a simple power transformer to convert 110 V AC to 18 V AC and you'll be up and running. No worry about polarity of the 18 V supply side because it's AC.

    Assuming that the power supply has plenty of current to deliver, the internal power supply circuitry may also include DC to DC up-converters to create 48 V DC, low current, for the Phantom power needed for condenser microphones. These DC to DC up-converters have come into play and become quite popular in recent years more so than in the past. It's now all on a microscopic chip. I would be surprised if that mixer does not offer Phantom power. Even if it only works off of an 18 V supply.

    Of course it's always desirable to have the company supplied unit. Thankfully, this kind of simple AC supply, only requires a simple transformer and the connectors you need. These transformers are available from companies like Newark Electronics, Digi-Key and others. This is a typical off-the-shelf readily available power supply transformer. You're going to pay a heftier fee for the factory supply. You don't need to. This is as simple as screwing in a lightbulb. No kidding.

    McMurphy
     
  6. Kurt Foster

    Kurt Foster Well-Known Member

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    your correct if you are all set up with a workbench and tools but not everyone is.

    ok so i get in the car drive 10 miles round trip to the radio shack (cause it's 5 miles up the road and 5 miles back)... i dick around finding a parking spot, buy the parts and ohh don't forget a soldering pencil, flux and solder because i don't have that stuff already ...

    then i go home and i go to put the parts together but i have to drill holes in the box so i get back in the car and i drive 10 miles round trip to home depot (cause it's 5 miles up the road and 5 miles back) and buy a drill and bits ..get back home and spend 2 or 3 hours putting it all together then i have to mickey mouse the connector on the mixer ... oops another drill bit ... back to home depot (another 10 miles) ... finally i get it all done and it works (maybe) or it fries the mixer (perhaps, because i really don't know what f i'm doing) but if it works it still looks like crud and is kludgy ... yeha i saved what? 20 bucks ... ohh but i drove 30 miles, spent 10 bucks on gas and and 25 bucks on parts and it took me 10 hours ....but wow i saved 10 dollars! ohhh i forgot ... the drill and bits cost me another 40 bucks and the soldering supplies were another $20... duh

    i know you mean well but sometimes you diy guys crack me up. for me, to not have to go through all that 45 bucks is cheap .. like the man said it's on sale .. get one while it's still 45 bucks the price is going to go up to 45 bucks soon!
     
  7. redcondurango

    redcondurango Active Member

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    Alesis multimix 8 usb FX psu.jpg
    Better late than never. There are still plenty of these kicking around and they offer some nice bang for your buck. Should you find one without its power supply unit never fear - here is the solution. The ebay reference for the three pin adapter was - 1Set M16 2/3/5/6/8Pins Screw Type Electrical Aviation Plug Socket Connector 400V. It will more likely than not come from the far east. Choose the 3 pin - obviously. See the image below for how to wire it up. There is a jumper between the two live positions, which is where the cable with the grey stripe is soldered. See the grey jumper . One position powers the phantom and the other the unit o coz there's only one power line you need to jump it round to the x 2 position for phantom power to microphones. Phantom on/off is on the front of the unit. The wall wart is also available on ebay - ALTO PRO ZMX52 MIXER 18V AC POWER ADAPTOR/SUPPLY/TRANSFORMER (KC AC-1800500) from poweradaptorsuk. Just search up the specs. I cut the end off the wall wart and soldered it up as per the image. It works fine. Watch out for surges to your speakers when switching on and off. Fortunately my monitors have a power up delay feature. Not sure if that surge is anything to do with the mod or the unit, which isn't earthed, seeing as there are only two wires. Go figure? The unit works though which is better than the dead unit which arrived on ebay minus its original psu which are nowhere available. Don't let anyone tell you this takes power via USB. Its old school 18V x 2 not 5V DC. Alesis multimix 8 usb FX psu.jpg
     
  8. Lee2020

    Lee2020 Active Member

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    In this picture the wire with white line is this the postive wire only asking as my power pack broke for my alesis multimix 6 fx but i have a few laptop power packs with adjustable voltage settings so wanting to wire one of them up to the original power connector socket just wanting to 100% before soldering and testing
     
  9. Boswell

    Boswell Moderator Well-Known Member

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    The Alesis spec for the Multimix 6FX power supply is 18.5 VAC at 700 mA. Note that it's a transformer only, providing an a.c. output, so no +ve and -ve.

    What are the specs of the laptop PSUs you have?
     
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  10. Lee2020

    Lee2020 Active Member

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    Theres 3 wires coming off the the transformer which are white brown and black reason im asking is the photo from a previous post shows a standard power pack with only two wires which is bridged across two of the connections so that made me think i could use a laptop power pack
     
  11. Lee2020

    Lee2020 Active Member

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    or are you able to tell me where the brown and blue wire go on the transformer as think i may have been a break in the wire that was the problem so if i could find this out maybe i could fix the original power supply
     
  12. Boswell

    Boswell Moderator Well-Known Member

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    Do you have any sort of battery-operated multimeter you could use to check a few things out?
     
  13. Lee2020

    Lee2020 Active Member

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    Yes mate sure have if you tell me what i need to test be very much appreciated.
     
  14. Lee2020

    Lee2020 Active Member

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    I did manage to work out where the blue and brown wire went as there was still a tiny piece of blue wire where it was cut off i soldered it all back together but still nothing so thinks its dead so i want to make a power pack from the picture i seen on here it shows using a standard power pack with only two wires which bridges across two of the points on the connector
     

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  15. Boswell

    Boswell Moderator Well-Known Member

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    You should establish whether any of the three wires coming from the power unit is mains earth. With the power unit unplugged from the mains, put the multimeter on Ohms range, and measure the resistance from the earth pin (longer than the others) on the mains plug to each of the three output wires in turn.

    If you get no continuity to any of the three, then either the earth wire is broken, or the mixer is unearthed and the three wires are all associated with supplying voltage to the mixer.

    The next step would be to plug the power unit into the mains but disconnected from the mixer. With the multimeter on an AC range of not less than 20V, measure the voltage between each pair of wires. Come back here with your findings.

    Good luck!
     
  16. alebro

    alebro Active Member

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    I've got a adapter with Multimix 12 that is a custom build and the pins as labelled on the connector are

    3 - 0 v
    2 - 9 v
    1 - 9 v

    I don't know if that adapter is suspect but when I use it with Multimix 12 the clip light is always lit. If I used a factory made official adapter with the mixer then the clip light is not on.

    I'm tempted to try an 18 v DC adapter (ex laptop) wired with positive to pin 1 and 2 and negative to pin 3. But before I try that I want to check if the custom built adapter is wired up correctly or has some other fault.

    Tn the custom build, the tabs on the transformer output side are

    1 - 0 v
    2 - 9 v
    3 - 0 v
    4 - 9 v

    1 is wired to 3 on the connector, 0 v
    2 is wired to 2 on the connector, 9 v
    4 is wired to 1 on the connector, 9 v

    Those 3 connections make sense, providing the 2 9 volt rails to the mixer power board. However the 3rd pin on the transformer is also wired to pin 2 on the connector.

    So pin 2 has 9 v and 0 v coming off the transformer which doesn't seem right, probably just a gap in my knowledge though!
     
  17. Boswell

    Boswell Moderator Well-Known Member

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    The transformer has two separate secondary windings, each of 9V. You need to connect these in series, so that you have an 18V centre-tapped output. You do this by connecting transformer pins 2 and 3 together and taking that to the mixer 0V input. The two outer pins (1 and 4) on the transformer then go individually to the two remaining inputs that are labelled 9V.

    First, disconnect all wires from the transformer secondary, then wire pins 2 to 3 and check that you get 18V a.c. between pins 1 and 4. It will probably read 20V - 24V on no load.

    DON'T USE THE LAPTOP SUPPLY, unless you have a rail splitter to generate the middle voltage.
     
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  18. alebro

    alebro Active Member

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    Apologies, this is misleading, there are no markings on the connector to label the voltages, just the numbers. After tracing each through to the transformer 9 v and 0 v points I assumed this was what they are on the connector but judging by what Boswell said about how windings configured in series that is not the case.

    So ignoring the voltages that I have incorrectly identified, the wiring of the connector pins in relation to the transformer pins is described correctly.

    (connector - transformer)
    3 - 0 v on pin 1
    2 - 9 v on pin 2 & 0 v on pin 3
    1 - 9 v on pin 4

    If I'm understanding correctly then, pin 2 on the connector is 18 v from the pair of 9 v transformer windings wired in series. So by my current understanding this means the connector pin voltages going into the mixer are actually

    3 - 0 v
    2 - 18 v from the 2 & 3 in series
    1 - 9 v

    I'm probably still missing something here because the label on the mixer says - 18V ~ 1000 mA X2 - which I read as 18 volts x 2

    Does this mean that the connector pin is actually 18 v as well because the way it is wired up the windings are in series on both the pins?

    Since I have an adapter that powers the mixer without the fault I will measure the voltages on the connector pins there and report back. I'd open it up and see what the configuration is at the transformer end but it's one of those glue sealed black boxes, not a screw in sight!

    Before I start sticking the multimeter into things, is it safe to connect 3 to 2, 2 to 1 and 1 to 3 as long as there is some resistance between them, i.e. the multimeter (and obviously keep my hands off the metal)?

    @Boswell thanks for all your help on this by the way, it's really appreciated!
     
  19. Boswell

    Boswell Moderator Well-Known Member

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    No, it's not safe. Don't connect anything to the mixer until you have verified the voltages with your meter.

    You need to find approx. 18V a.c. between two of the pins, and then half of that separately between each of those two pins and the third pin (the centre-tap). The only way a simple measurement can tell you the phase of the windings relative to one another is to connect one end of a winding to an end of the other winding. When you measure between the two open pins, you will either see 18V or almost zero. If the former, you have correctly got the windings in series and the same phase. If the latter, you have got the phases opposing, and they are cancelling out.
     
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  20. alebro

    alebro Active Member

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    I mean to measure the pins on the connector that goes into the mixer but not with the mixer plugged in.

    The transformer would be plugged to mains only and I'd use the multimeter to get a reading of what is on each of the pins coming from it. By "connect 1 to 2, 2 to 3 etc" I mean reading the voltages between 1 and 2, 2, and 3, 1 and 3. Sorry my terminology is all over the place!
     
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