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-   -   +8V unregulated? (http://www.diyaudio.com/forums/parts/117475-8v-unregulated.html)

PhantomBox 15th February 2008 06:32 AM

+8V unregulated?
 
Hello there.
Someone gave me a couple of Sony MXP-3000 module in order tho get them racked.
I'm starting whith the PSU for these modules, and found something that I don't quite understand.
It may sound stupid to you, but - as far as I can remember - I've nerver seen this term on any schematic diagram or even printed on a motherboard before and I have turned quite some high-end consoles into rackunits.

Here it is: What exactly does "+8V unreg(ulated)" mean?
(on the motherboard it says +48V, +18V, AUDIO GND, -18V, +24V, PERIPH GND, CHASSIS GND, +8V UNREG and DIGITAL GND, I might use +48V, +18V, -18V, +24V and just a general GND)

PhantomBox

dave_gerecke 15th February 2008 11:08 PM

Hello PhantomBox, I would think the meaning is that it is a 8VDC power supply without any active device like a pass transistor or voltage regulator (LM317, etc.) in the path from the rectifier and filter capacitors to the terminal on the board. From the sounds of the labelling, the rest of the power lines going to the board have some sort of regulation to maintain the voltage going into terminal at the voltage specified. For some reason the 8VDC line doesn't need to be regulated. Perhaps the regulator is somewhere on the PCB that the wire attachs to. To get a voltage of this value, the transformer would have an AC voltage of around 6 volt AC on the secondary. This is a little high in voltage, but since there is some voltage drop across the diodes in the rectifier, this will bring the voltage down to the 8 volt dc range after rectification and filtering.

Hope this helps,

Dave


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