Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default what is the difference btn -48volts and 48volts power supply?

l wish to know the difference between negative 48 volts and the normal 48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks
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Default what is the difference btn -48volts and 48volts power supply?

On 2016-01-21, wrote:
l wish to know the difference between negative 48 volts and the normal
48 volts.


The difference is 96 volts. Is this a trick question?
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Default what is the difference btn -48volts and 48volts power supply?

wrote:

l wish to know the difference between negative 48 volts and the
normal 48 volts.
Also l will be glad if a could have a circuit for a regulated
-ve 48 volts power supply at 3A. thanks



** Those two requests ought not be in the same post from the same person.



..... Phil



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Default what is the difference btn -48volts and 48volts power supply?

On Thu, 21 Jan 2016 04:33:29 -0800, Phil Allison wrote:

wrote:

l wish to know the difference between negative 48 volts and the normal
48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48
volts power supply at 3A. thanks



** Those two requests ought not be in the same post from the same
person.


Well spotted. Does seem a bit odd.

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Default what is the difference btn -48volts and 48volts power supply?

On Thursday, January 21, 2016 at 12:13:52 AM UTC-5, wrote:
l wish to know the difference between negative 48 volts and the normal 48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks


Think of voltage as pressure. 5 pounds of pressure pushing electrons or 5 pounds of vacuum pulling electrons is the difference between 5 volts negative and 5 volts positive. This is not a perfect analogy but it will get you there. Current , amps , is the number of electrons moving. Wattage is amps times voltage so a voltage of 48 at 3 amps , full throttle , is 48 V times 3 A for 144 watts. Write this down and memorize it and Bob's your uncle. Also there is no such thing as a dumb question.
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Default what is the difference btn -48volts and 48volts power supply?

On Wednesday, January 20, 2016 at 9:13:52 PM UTC-8, wrote:
l wish to know the difference between negative 48 volts and the normal 48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks


Thanks a lot Jeff you've actually given me a good understanding. so I can build a normal 48 volts supply and ground the positive terminal instead.
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Default what is the difference btn -48volts and 48volts power supply?


wrote in message
...
On Wednesday, January 20, 2016 at 9:13:52 PM UTC-8,
wrote:
l wish to know the difference between negative 48 volts and the normal 48
volts.
Also l will be glad if a could have a circuit for a regulated -ve 48
volts power supply at 3A. thanks


Thanks a lot Jeff you've actually given me a good understanding. so I can
build a normal 48 volts supply and ground the positive terminal instead.


That is right. Just build any power supply that will meet your needs and do
not ground any of the components in it. That isolates it from the chassies.
The ground the positive output instead of the negative output.

While not usually as high as 48 volts the 3 terminal regulators are made for
the negative as well as the positive output. The leads are sometimes in
different places and most of the diodes and capacitors are just reversed.
That is often the way unregulated supplies are made.


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Default what is the difference btn -48volts and 48volts power supply?

On 2016-01-21, John Heath wrote:
On Thursday, January 21, 2016 at 12:13:52 AM UTC-5, wrote:
l wish to know the difference between negative 48 volts and the normal 48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks


Think of voltage as pressure.


.... and as you gradually ease into thinking of voltage as pressure,
relax and concentrate on supressing that strange feeling that makes you
want the schematic for a "regulated power supply", even though you don't
know WTF that means.


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Default what is the difference btn -48volts and 48volts power supply?

It turns out that -48 V is less corrosive. that's why it's used.

the voltage is "relative". Lots of wall warts might have a coaxial power connector. Some may have center positive and others the outside positive.
How you hook it up depends on the circuit.

A -48 supply may indeed have the positive side grounded, but it may not.

A +-12 V supply has a common point and when you measure to that common point you get the +12 and -12 voltage. But that common point may not yet been grounded.

An isolated 48 V supply can generally be connected either way.
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