Bennett Price wrote:
Some devices have connectors that put the - voltage on the center pin,
others put + on the center pin. (For center pin, you can substitute big
pin/socket, funny looking pin/socket, yellow pin/socket, etc.)

In your PC, the power supply is generating both +12 and -12 volts -
there's an instance where both voltages are needed - rather than just
swapping the + and - pins.

Distintinguish between ground and minus. Ground in electronic equipment
like
radios and PCs can be either positive or negative. If the negative pole
of a power supply in a radio is tied to the metal chassis (or the common
areas of a PC board, then you can say ground is negative. Alternately,
if the supply's positive voltage is connected to the chassis or the
common areas of a PC board, you can talk about a positive ground.
In a PC, which uses both positive and negative 12 volts, each is
measured in relation to ground (chassis/common) - thus if you connect a
voltmeter's black/negative lead to the chassis, you'll measure +12 at
certain points and -12 at others. If you clip the voltmeter to the +
and - wires, you'll measure 24 volts.

Have you considered a trip to your local public library for an
elementary book on electricity?






sorry for all the chat, I have already purchased some 12 textbooks on
electronics but i am avoiding my basic electronics book that i had more
than 15 years ago already cause basic electronics is more difficult
than advanced electronics to me. I am pretty much using Electronics
Workbench to get me past all the math and common sense. Sure i'm gonna
get electrocuted some day......but if i ground myself at all times, the
most i'll lose are a few eyebrows and maybe a few tongue taste buds and
ear follicles. I just won't do electrical that's all. Stick to digital
low volts stuff for now. Avoid industrial robotics.

at any rate, i ended up parchasing a cheap switcheable universal cause
the variable at fry's turned out to be a switcheable. So i just went
cheap and will save my money for a good Elenco or something affordable
yet professional. I'm gonna run this through my scope and tell you all
what the ripple is on single then coupled power supplies.

thanks for your help. Really appreciated it cause i did in fact review
my basic electronics book (among others) and it didn't have anything on
DC designs.








you can probably just reverse the leads on one of the connections. So a
parallel circuit/device goes minus plus, the other parallel device goes
plus minus. The classic reverse parallel dive. Guess though these would
have to share current. Maybe those professional power supplies devices
are isolating the ground for some reason. Perhaps for less noisy
signals. Is it possible to have a positive ground? Or is that just as
Seussian as DC peaks? Thanks for your replies by the way.