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Soundcraft Spirit Notepad power input?

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Ryan94 View Drop Down
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    Posted: 11 July 2013 at 1:20pm
Hi Guys,

Ive been given a Soundcraft spirit notepad to repair the power input on it, the owner broke the original power connector so cut the original one of with the plan to solder on a new one, however they didn't mark which wire was which and therefore got confused and gave it to me to look at. By the looks of it these use a + and - 17VAC supply so therefore there are three wires instead of the two they expected. ive tried looking for schematics but cant seem to find any on the net, was just wondering if anyone had ever worked on one a know which wire is the +17v supply, which is the -17V supply and which is 0V. 
Theres a picture bellow of the connections on the board. 


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Ryan
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 1:38pm
Logic would suggest the red wire is +17, the green wire is 0v and the black is -17? Unless Soundcraft use a different convention to the rest of the world! A simple test would be to identify the + supply pin on an opamp chip near the power input, and test for continuity between that pin and one of the wires; similarly, the audio ground, ie any audio connector ground contact, should have continuity back to the 0v wire.
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Ryan94 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ryan94 Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 2:34pm
Thanks for the reply, i will have a go at what you have said and let you know how i get on.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JR.junior Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 6:26pm
black is ground.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 6:54pm
"+ and - 17VAC supply"

Does the board have a bridge rectifier or diodes? If so, there is no +/- as such, you just need to identify the earth. Otherwise, does it have any kind of voltage regulation? That will then tell you the polarity. Otherwise as above - check continuity to the supply pins on one of the ic´s.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 10:31pm
This does not use a DC supply, it has onboard rectification and regulation.

You need a supply that will give around 17 - 0 - 17 VAC . A  transformer with a pair of 18V windings works fine, that's what I use on my Folio.

Having just taken mine apart to have a look, ithe GREEN wire (which went to the middle pin of the connector) is ground and the other two are the 17 or 18V AC connections.

HTH.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2013 at 11:17pm
Its a 17-0-17 transformer (with thermal overload) that you need. That's why the capacitors etc are on the mixer board.

You could use an off the shelf 17V transformer (if you can find one) but do find some way of stopping it catching fire if the lead or mixer shorts out won't you.



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Lab View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lab Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2019 at 5:05pm
Hello I am French, sorry for my English. I dig up this post because, I have a Notepad mixer whose life I would like to save, (enough waste ...) I no longer have food. Knowing, given the previous publications, that the notepad can be supplied with 17 or even 18 V. Can you tell me if this one (see photos) could be suitable, it's 19v under 2.64 A I think. thank you in advance
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2019 at 1:50pm
I can't see a picture, but it sounds like you are describing a 19v DC laptop supply, which will not be suitable at all. 

You need a centre tapped 17-0-17v AC transformer. Because it is AC, it will not be important which way  the two 17v wires go - only that the centre tap 0v is connected to ground.

A small one will do. 25VA would be adequate.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lab Quote  Post ReplyReply Direct Link To This Post Posted: 22 December 2019 at 9:30pm
Thank you very much for your answer. ..However, could you possibly advise me on a product, easy to find, which could substitute for the original adapter ... Thank you in advance
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2019 at 2:09pm
You will probably have to build something. The original adapter has a strange connector so there aren't any direct replacements.

So, search for "transformateur CA 17-0-17v" and buy a small 25-30VA one. Then, you will need a box to mount it in, some 1.5mm 3-core cable to wire it up, and some cable grommets or glands to pass the cables in and out of the box.

Mains live and neutral are connected to the two primary wires on the transformer (via thermal switch, see below). Mains ground is connected to the 0v secondary centre tap, and any exposed metalwork on the box. The three secondary wires (2x17v, 0v) are connected to your chosen output connector.....

To replace the Soundcraft connector, you'll need to open up the mixer, and desolder and remove it. Then, use a short length of cable to solder on another locking female connector with at least 3 pins. A 4-pin XLR is a good choice, to avoid confusion with microphone connections. You can choose which pins to use, there isn't a standard. Then, use another cable grommet to secure the new connector's short cable to the mixer.

As kedwardsleisure says above, you really also need a thermal overload protector on the transformer too. These can be found easily, probably from the same place you buy the transformer. The mains live connection is wired through the thermal switch, which is secured to the transformer inside the box. So, if the transformer overheats, mains power is disconnected.

Hope you can follow that! Good luck :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lab Quote  Post ReplyReply Direct Link To This Post Posted: 02 January 2020 at 9:44am
Hello thank you very much i will try to follow...
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