Triple Output Power Supply Voltage with no load resistance

C

Chris

Guest
Hi all.
I just got a used triple output supply and the two variable supplies do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not because
they are dead. The fixed 5V supply outputs a constant voltage though which
makes me think that the variable channels might be broken. Can anyone help
me out on this?
Chris
 
I read in sci.electronics.design that Chris
<Konnector@novalid.email.com> wrote (in <newscache$sbq9vh$k9b$1@news01b.
so-net.ne.jp>) about 'Triple Output Power Supply Voltage with no load
resistance', on Sun, 28 Mar 2004:
Hi all.
I just got a used triple output supply and the two variable supplies do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not because
they are dead. The fixed 5V supply outputs a constant voltage though which
makes me think that the variable channels might be broken. Can anyone help
me out on this?
Click to expand...
Insufficient data. What are the manufacturer and the model number of the
product?

--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
Chris wrote:
Hi all.
I just got a used triple output supply and the two variable supplies do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not because
they are dead. The fixed 5V supply outputs a constant voltage though which
makes me think that the variable channels might be broken. Can anyone help
me out on this?
Chris
Click to expand...
You might try a load resistor...
I can't imagine a commercial variable benchtop power supply that
wouldn't regulate with
no external load. Methinks you're busted.
mike

--
Return address is VALID.
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Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
Chris wrote:
Hi all.
I just got a used triple output supply and the two variable supplies do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not because
they are dead. The fixed 5V supply outputs a constant voltage though which
makes me think that the variable channels might be broken. Can anyone help
me out on this?
Chris
Click to expand...
It may help to remove those shorting jumpers on the output terminals,
and then try it.
 
Sorry about the lack of info. Its an Instek PC-3030D triple output power
supply. It won't regulate under no load. I am hoping that it is some analog
thing that I am unfamiliar with. Otherwise, I am SOL. Thanks for the
feedback. Any suggestions?
Chris
 
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"Chris" <Konnector@novalid.email.com> wrote in message
news:newscache$c7javh$dgh$1@news01b.so-net.ne.jp...
Sorry about the lack of info. Its an Instek PC-3030D triple output
power
supply. It won't regulate under no load. I am hoping that it is some
analog
thing that I am unfamiliar with. Otherwise, I am SOL. Thanks for the
feedback. Any suggestions?
Chris
Click to expand...
It sounds like it's bad to me. You probably need to replace the output
transistors. They often get blown when someone connects up a PS to
another power source.
 
mike wrote:
Chris wrote:

Hi all.
I just got a used triple output supply and the two variable supplies
do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not
because
they are dead. The fixed 5V supply outputs a constant voltage though
which
makes me think that the variable channels might be broken. Can anyone
help
me out on this?
Chris



You might try a load resistor...
I can't imagine a commercial variable benchtop power supply that
wouldn't regulate with
no external load. Methinks you're busted.
mike
Click to expand...
One more thing.
Sometimes the remote sense doesn't have an internal shunt resistor...bad
design...but I digress...
It's used in an application that has remote sense. Gets removed, sent
to surplus without reconnecting the sense leads on the back panel.
Check the back panel connections for sense connections. Some have a
switch for internal/external sense.
mike


--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
"Chris" <Konnector@novalid.email.com> wrote in message news:<newscache$sbq9vh$k9b$1@news01b.so-net.ne.jp>...
Hi all.
I just got a used triple output supply and the two variable supplies do not
change voltage when I turn the dial. I am hoping that this is due to the
fact that there is no load resistance across their terminals and not because
they are dead. The fixed 5V supply outputs a constant voltage though which
makes me think that the variable channels might be broken. Can anyone help
me out on this?
Click to expand...
Most triple-output supplies have an option to make the two variable
supplies track each other. This option is usually selected by either
or both a switch and a shorting strap.

Are the two supplies tracking each other? What are they putting
out, anyway? No shorting straps installed plus-to-minus between the two?

The variable supplies usually are completely independent and float
relative to each other except for the tracking feature. So anything
that affects both supplies usually implies the tracking stuff isn't
doing what you want. I'm not so sure that it means that it's broken, it
may just be a case of "operator error".

Tim.
 
"Chris" <Konnector@novalid.email.com> wrote in message
news:newscache$sbq9vh$k9b$1@news01b.so-net.ne.jp...
Hi all.
I just got a used triple output supply and the two variable supplies do
not change voltage when I turn the dial. I am hoping that this is due to
the fact that there is no load resistance across their terminals and not
because they are dead. The fixed 5V supply outputs a constant voltage
though which makes me think that the variable channels might be broken.
Can anyone help me out on this?
Chris
Click to expand...

Not sure if this applies to your PSU, but I've seen some commercial PSUs
having the (+) and (-) sense connectors next to the (+) and (-) output
connectors, and use some kind of metal pieces - like paperclips - which
connect the sense to the output. When you want to use the sense feature you
remove them as necessary. Could it be that these are missing in your PSU? If
so, the regulator won't get any voltage feedback and so won't be able to
regulate. If your PSU has remote sense connectors, try to connect them to
the output and see if that works.

cheers,
Costas
 
"Costas Vlachos" <c-X-vlachos@hot-X-mail.com> wrote in message
news:c47oig$egm$1@sparta.btinternet.com...
"Chris" <Konnector@novalid.email.com> wrote in message
news:newscache$sbq9vh$k9b$1@news01b.so-net.ne.jp...
Hi all.
I just got a used triple output supply and the two variable supplies
do
not change voltage when I turn the dial. I am hoping that this is
due to
the fact that there is no load resistance across their terminals and
not
because they are dead. The fixed 5V supply outputs a constant
voltage
though which makes me think that the variable channels might be
broken.
Can anyone help me out on this?
Chris
Click to expand...

Not sure if this applies to your PSU, but I've seen some commercial
PSUs
having the (+) and (-) sense connectors next to the (+) and (-) output
connectors, and use some kind of metal pieces - like paperclips -
which
connect the sense to the output. When you want to use the sense
feature you
remove them as necessary. Could it be that these are missing in your
PSU? If
so, the regulator won't get any voltage feedback and so won't be able
to
regulate. If your PSU has remote sense connectors, try to connect them
to
the output and see if that works.
Click to expand...
But most PSes I've seen have a 10 ohm or so resistor between the output
and sense terminals, so if the straps are left off, all that happens is
that it won't be as accurate as it was with them on. The 10 ohm
resistors look like an open when compared to the milliohms resistance of
the output and sense wires.


cheers,
Costas
Click to expand...
 
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