Hello,
I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.
Thnsk, Ali

Could be anything, but just remember most voltage supplies these days are
unregulated so they will drop with any load across them.

"alitonto" wrote in message
oups.com...
Hello,
I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.
Thnsk, Ali

Easy reminder..the higher the resistance, the higher the voltage drop,
and vice versa. You disconnect the circuit (infinite resistance), and
the voltage increases to supply. If you are not reading expected
voltage, check resistor values, zener diodes in supply. Good luck.

alitonto wrote:

I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.

Along with all the other suggestions, you might get lucky if you feel for
not-normally-warm components, which will give you a clue as to which area to
look in.

If the supply in question is fairly low impedance, there won't be enough heat
to feel, so you'll need to cut tracks and remeasure, in an attempt to find
which branch is pulling it down.

At one stage, we were lucky and had use of a thermal imaging camera. You can
spot warmer components quite easily that way. Though not probably the cheapest
specific-use diagnostic equipment... :-)
--
Linux Registered User # 302622 http://counter.li.org

Ahhh John, with this guys apparent level of knowledge do you think that is such a
good suggestion? Especially if it is a switched power suppy

David - who hopes alitonto has the sense to realise he has to switch off and
unplug the power lead from the mains before he starts feeling around for warm
componants with his fingers

David

John Tserkezis wrote:

alitonto wrote:

I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.

Along with all the other suggestions, you might get lucky if you feel for
not-normally-warm components, which will give you a clue as to which area to
look in.

quietguy wrote:

Ahhh John, with this guys apparent level of knowledge do you think that is such a
good suggestion? Especially if it is a switched power suppy

David - who hopes alitonto has the sense to realise he has to switch off and
unplug the power lead from the mains before he starts feeling around for warm
componants with his fingers

Whoops, sorry. I've been working on low-voltage equipment for so long now,
that I've forgotten that you can get killed for what I get away with now...

However, common sense applies, and I'm not going to append a disclaimer to
the end of all of my messages.

This isn't the US. Yet.
--
Linux Registered User # 302622 http://counter.li.org

"alitonto" wrote in message
oups.com...
Hello,
I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.

Generally, three things can be considered here. (1) V=IR so if I, the
current, or R, the resistance is too high, V, the voltage drop, will be
excessive. (2) Some power supplies use current limiting which kicks in at a
given point and then they switch over to a constant current mode (as opposed
to constant voltage mode). (3) Some power supplies use fold-back current
limiting which also kicks in at a given point but the current folds back
which makes the voltage drop at the load even more severe.

Could be the load is partly shorted, or a series resistance has gone up in
value, or a faulty connection, or a faulty power supply. Troubleshooting is
usually a process of elimination.

Thanks guys,
The supply voltage to this circuit is meant to be 5 volts (as per
schematic);
now when I disconect the load (circuit ahead) then should that 5 volts
actually measure a bit higher than stated?
Ali




"Charles Schuler" wrote in message ...
"alitonto" wrote in message
oups.com...
Hello,
I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.

Generally, three things can be considered here. (1) V=IR so if I, the
current, or R, the resistance is too high, V, the voltage drop, will be
excessive. (2) Some power supplies use current limiting which kicks in at a
given point and then they switch over to a constant current mode (as opposed
to constant voltage mode). (3) Some power supplies use fold-back current
limiting which also kicks in at a given point but the current folds back
which makes the voltage drop at the load even more severe.

Could be the load is partly shorted, or a series resistance has gone up in
value, or a faulty connection, or a faulty power supply. Troubleshooting is
usually a process of elimination.

Be carefull !!!!!

Some here are really assassins !!

Take the power plug off, deconnect the power supply.

Put a digital voltmeter in continuity test mode (beeep ...) and test
all the capacitors. NOT ON THE POWER SUPPLY IT SEEMS OKAY !!!

Should beeb shortly in normal stat. If beeping continuously, the
capacitor is shorted.

"alitonto" wrote in news:1108475705.096838.197480
@z14g2000cwz.googlegroups.com:

Hello,
I am trying to work out in particular which component is most likely to
cause a reduced voltage at the supply point to its circuit. I suspect
there is something pulling too much current ahead, becuase when I
disconnect the circuit then the supplied voltage returns to normal
measurement.
Thnsk, Ali


I've read the other posts and unless I'm missing something, there is not
enough info from the OP to determine the type of power supply, the voltage
etc. so giving advice is ****ing on the wind and guessing what the real
problem is. Can the OP elucidate his problem for the group?