Power LED

  • Thread starter Thread starter Bill
  • Start date Start date
Ralph said:
As always it depends. If it is bad because it is shorted then it will keep
the suppply from comming on. If it is open then no it will not , if it is
plugged in backwards it will not , if it is plugged in where it shouldn't
then maybe yes or no. Just unplug it if it is plugged into anything and see
what hapends.
The computer does not need it to run.
Click to expand...
The LED has a current limiting resistor otherwise the LED would be
destroyed once power were applied. LEDs operate with about 8 ma. It is
very unlikely that even if an LED were shorted that it would prevent the
power supply from starting up due to this limiting of the current for
the LED. I don't like people who feel they must correct posters when
they make an error, but I thought you might want to know about this fact.
 
Bill said:
Will a bad power led keep the power supply from coming on? Thanks.
William
Click to expand...

As always it depends. If it is bad because it is shorted then it will keep
the suppply from comming on. If it is open then no it will not , if it is
plugged in backwards it will not , if it is plugged in where it shouldn't
then maybe yes or no. Just unplug it if it is plugged into anything and see
what hapends.
The computer does not need it to run.
 
The LED has a current limiting resistor otherwise the LED would be
destroyed once power were applied. LEDs operate with about 8 ma. It is
very unlikely that even if an LED were shorted that it would prevent the
power supply from starting up due to this limiting of the current for
the LED.
Click to expand...

What if the shorted LED prevents the motherboard from initializing,
keeping the PS PS_On signal pulled low, would that not have same end
result of the power supply not turning "on".
I don't like people who feel they must correct posters when
they make an error, but I thought you might want to know about this fact.
Click to expand...

What would keep urban legends, bad advice or other misc falsehoods and
technical errors from having a negative impact if the errors aren't
corrected or at least discussed? Everyone's wrong every now and then, but
to learn from that, the error must be pointed out... fact over ego, so
long as it's _useful_ in some way.
 
The LED has a current limiting resistor otherwise the LED would be
destroyed once power were applied. LEDs operate with about 8 ma. It is
very unlikely that even if an LED were shorted that it would prevent the
power supply from starting up due to this limiting of the current for
the LED. I don't like people who feel they must correct posters when
they make an error, but I thought you might want to know about this fact.
Click to expand...

I am well aware of the way a LED operates. I work as an instrument mechanic
in a very large factory. I deal with most aspects of electricity and
electronics from computers to 480 3 phase circuits at 600 amps.

I was thinking of the whole LED system from the plug out. I did see one
computer where some wires going to the led was shorted and there was enough
current to heat up and burn the insulaton off the wires.
 
kony said:
What if the shorted LED prevents the motherboard from initializing,
keeping the PS PS_On signal pulled low, would that not have same end
result of the power supply not turning "on".
Click to expand...

How would a shorted "Power" LED prevent the MB from initializing?

[And, BTW, a low signal for the PS_ON *is* the "turn on" signal. A high
state signal on the PS_ON pin is the "turn off" signal.]
What would keep urban legends, bad advice or other misc falsehoods and
technical errors from having a negative impact if the errors aren't
corrected or at least discussed? Everyone's wrong every now and then, but
to learn from that, the error must be pointed out... fact over ego, so
long as it's _useful_ in some way.
Click to expand...

Glad you feel that way. <g>
 
ric said:
How would a shorted "Power" LED prevent the MB from initializing?
Click to expand...

Try putting your Power LED across the +5v and ground jumpers on your jumper
block.

Of course that's the the right place for it, but it will definately stop the
PC from booting up!
 
On Sat, 03 Apr 2004 20:06:44 GMT, "Bill" <[email protected]>
wrote:

No, but if the Hard drive gets no power it will not light up. If the
hard drive LED Leads are backward it may not light up.
 
How would a shorted "Power" LED prevent the MB from initializing?
Click to expand...

Don't know, was why I wrote it in the form of "what if". Doesn't the LED
get controlled by the chipset due to multiple states of power management?
It's not just a connection to the power plane through a resistor, AFAIK,
so it's not an issue of the power supply lines being shorted regardless of
the LED resistor, it would be a logical issue, IF it's an issue.
[And, BTW, a low signal for the PS_ON *is* the "turn on" signal. A high
state signal on the PS_ON pin is the "turn off" signal.]
Click to expand...

True, I worded the above a bit awkwardly, the part about "keeping the PS
PS_On signal pulled low" was meant as a 2nd consequence, the prevention of
.... keeping it pulled low.
 
Noozer said:
Try putting your Power LED across the +5v and ground jumpers on your jumper
block.
Click to expand...

Then it would just be "a LED", not the "Power LED." And it would not be
shorted for long. It would soon be open.
Of course that's the the right place for it, but it will definately stop the
PC from booting up!
Click to expand...

Only momentarily. <g>
 
kony said:
Don't know, was why I wrote it in the form of "what if". Doesn't the LED
get controlled by the chipset due to multiple states of power management?
It's not just a connection to the power plane through a resistor, AFAIK,
so it's not an issue of the power supply lines being shorted regardless of
the LED resistor, it would be a logical issue, IF it's an issue.
Click to expand...

No matter, it would have a dropping resistor in series with it. If the
LED shorted, the dropping resistor would just have the additional ~2v
across it. I doubt that the chipset would even be aware of it.
 
Thanks to all. I did unplug all leads from front panel connector except for
the power on switch. Computer comes on now. I just installed a new Mother
board is the reason for the question. However, even though the system boots
up and goes to winME my PCI cards don't work, my CDRW drive, DVD drive don't
show up in My Computer and my primary HD and my second HD is in Dos
compatibly mode. Probably something in BIOS I don't have set correctly. Can
anyone help? Thanks.

Bill
 
Thanks to all. I did unplug all leads from front panel connector except for
the power on switch. Computer comes on now.
Click to expand...
I just installed a new Mother board is the reason for the question.
Click to expand...
However, even though the system boots
up and goes to winME my PCI cards don't work, my CDRW drive, DVD drive don't
show up in My Computer and my primary HD and my second HD is in Dos
compatibly mode. Probably something in BIOS I don't have set correctly. Can
anyone help? Thanks.

Bill
Click to expand...

To clarify, you had the system running WinME, then swapped the motherboard
and are trying to continue using the same installation of WinME?

If so, you need to clear out the Plug-N-Played hardware from the previous
board, have Windows redetect the current board's hardware, then delete any
duplicate flagged entries in Device Manager and install chipset driver(s).

The above is the condensed description, since it's not clear yet that this
is what you're wanting/needing to do.
 
Yes that is exactly what I did and what I want to do. Before I clear out
anything, I failed to mention that I tried to use Add New Hardware in
Control Panel and it wouldn't run. Is that because of the new Mother Board?
How do I clear out everything? Thanks.
Bill
 
Yes that is exactly what I did and what I want to do. Before I clear out
anything, I failed to mention that I tried to use Add New Hardware in
Control Panel and it wouldn't run. Is that because of the new Mother Board?
How do I clear out everything? Thanks.
Click to expand...


Unless you have something very unusual, an old legacy device that's not
Plug-n-play compatible, you probably won't need to use "add new hardware"
at all.

If you have software specific to the odd motherboard loading at boot, for
example a hardware monitor (temp, voltage, etc) type program then disable
that from loading at the next opportunity. Add/Remove programs (or
whatever method is applicable) can be used, and while in Add/remove
programs, uninstall any drivers/etc appearing there that were specific to
the other motherboard, including chipset drivers.

Then the easiest method to clear out old hardware entries is to delete a
subkey from the registry. Use REGEDIT to highlight the
HKEY_LOCAL_MACHINE\ENUM key, and delete it.
Here is an example:
http://69.36.189.159/hklm_enum.gif

After doing this you "may" need to recreate a registry key to get a newer
WDM-type sound card working. If that's the case then merge the following
file into the registry... filename suggests Win98 but the two OS aren't
that different.
http://69.36.189.159/usr_1034/Win98_WDM_Sound.reg

After deleting that registry key you'll be rebooting the system, letting
it redetect hardware and installing drivers. It's beneficial to have the
WinME installation files as well as hardware drivers available on the hard
drive, in the beginning you may not have access to an optical drive.
Later drivers like video, sound, modem, etc, do not have to be on the hard
drive.

So after a few hardware detections you'll reboot a few times, and then go
into Device Manager and delete any duplicate devices where one of the two
has an exclaimation mark... after rebooting again the correct device will
be redetected. Basically you'll just be rebooting several times and
letting windows do it's Plug-N-Play thing, pointing it to any drivers it
can't find. After the machine has finished detecting all hardware, don't
forget to install the motherboard chipset driver(s).
 
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