switching power supply.. can't get -24v? - diyAudio
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Old 20th February 2012, 12:54 PM   #1
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Default switching power supply.. can't get -24v?

I am fairly new to this.

Can anyone help me setup a switch mode power supply to test my pcb with. I have everything populated but when I go to hook it up...the way i think is correct i can't seem to get -24 volts? I seem to get +24 fine.

Where do i connect the ground wires on the pcb directly to psu? pcb ground to chassis.

any help is appreciated
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Old 20th February 2012, 03:12 PM   #2
6L6 is offline 6L6  United States
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Mr. Bulls Hit,

Is it a single SMPS? I doubt you can make a bipolar supply with it.

Also, it would be of great help to know what you are building...
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Old 20th February 2012, 03:29 PM   #3
Zen Mod is offline Zen Mod  Serbia
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pics , pretty please

presuming that your switching PSU is +24Vdc , you'll need two of them for bipolar supply

in stacked arrangement

but , clarify , so we can help
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Old 20th February 2012, 05:02 PM   #4
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Greetings.

I will try to attach photos... see attached

power supply is UAW250S:
http://www.cosel.co.jp/en/products/pdf/SFE_UAW.pdf


It is aleph J pcb I want to start up
Attached Images
File Type: jpg SAM_1718.jpg (154.5 KB, 189 views)
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Old 20th February 2012, 05:16 PM   #5
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It's only a single 24V supply so you would need two of them to provide + and - supplies.

I note you already have two of them, I presume you have one for each amp.

I have to assume that the outputs are electrically isolated from each other.

Try connecting V+ of one to V- of the other and use this common connection for 0V. Then use the unused V- and V+ as your -24V and +24V supplies.

Last edited by KatieandDad; 20th February 2012 at 05:19 PM.
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Old 20th February 2012, 05:20 PM   #6
Zen Mod is offline Zen Mod  Serbia
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you need to stack two of them to have bipolar PSU

+V of first is +24v

-V of second is -24V

connect bridge between -V of first and +V of second , and that's system audio GND
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Old 20th February 2012, 05:23 PM   #7
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There's an echo in here.
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Old 20th February 2012, 05:24 PM   #8
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Thanks for everyones replies.

I will look for a single dual power supply.. I have two of these 1u power supply but i do not want to use two because it will be too big for my chassis unless i mount into seperate chassis like in the photo it now looks big and ugly LoL

Again thanks I will try Kate and Dad's suggestion first.
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Old 20th February 2012, 05:28 PM   #9
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According to the datasheet these SMPS's are single output.

Your last picture shows FG (frame ground) connected aswell as + and -.
To hook up the right way is to connect the + from one PS unit to the - of the other. This connection will be GND for the amplifier! Then take + from one and - from the other unit (those that were NOT used to connect GND).

Pls check the SMPS frame if it is connected to the -. If this is not the case then proceed. The FG terminals connect to earth.

If the case is connected to - then one PS must be mounted insulated.
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Old 20th February 2012, 05:28 PM   #10
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I also have another question as for RCA input... do I bridge -In to ground?

Thanks again guys not too much BS around here today
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