A couple months ago I built myself a new computer and for some reason,
the power indicator LED stays on for about 20 seconds (when I first
turn the computer on). After that, it flickers and goes out. I've
hooked it up to 3 different locations on the motherboard and the
results have all been the same. What could be causing the LED to go
out?
Bryan

wrote in
:

A couple months ago I built myself a new computer and for some reason,
the power indicator LED stays on for about 20 seconds (when I first
turn the computer on). After that, it flickers and goes out. I've
hooked it up to 3 different locations on the motherboard and the
results have all been the same. What could be causing the LED to go
out?

In decreasing order of probability.

A bad LED.
A bad resistor in series with the LED.
A bad wire or plug.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

bz wrote:
wrote in
:

A couple months ago I built myself a new computer and for some reason,
the power indicator LED stays on for about 20 seconds (when I first
turn the computer on). After that, it flickers and goes out. I've
hooked it up to 3 different locations on the motherboard and the
results have all been the same. What could be causing the LED to go
out?

In decreasing order of probability.

A bad LED.
A bad resistor in series with the LED.
A bad wire or plug.

The OP need to measure the voltage across the led. If it disapears or
drops after 20 seconds, it`s probably the Mobo. If the led goes out but
the voltage is still present, it might be that the current limiting
resistor is insuficient and the led is thermalling.


Ron(UK)

wrote:
A couple months ago I built myself a new computer and for some reason,
the power indicator LED stays on for about 20 seconds (when I first
turn the computer on). After that, it flickers and goes out. I've
hooked it up to 3 different locations on the motherboard and the
results have all been the same. What could be causing the LED to go
out?

Could possibly be a software problem (Are power LEDs available to
software control?). Does it still turn off if you stay in the BIOS
screen, instead of booting your operating system?

Cheers,
Nicholas Sherlock

It can't be the motherboard. Because I also tried connecting the LED
to the amplifier board (for the internal speaker) which is completely
independent of the motherboad. The results were the same...the LED
stayed lit for about 20 seconds, then gradually flickered out. The LED
came from an assortment package I bought at Radio Shack. Should I just
try another one?
Bryan

wrote in news:aaa47d9a-893d-4ccd-be08-c75bdc8ce708@
8g2000hsu.googlegroups.com:

It can't be the motherboard. Because I also tried connecting the LED
to the amplifier board (for the internal speaker) which is completely
independent of the motherboad. The results were the same...the LED
stayed lit for about 20 seconds, then gradually flickered out. The LED
came from an assortment package I bought at Radio Shack. Should I just
try another one?

That would probably be the quickest thing to try, wouldn't it?

Question: did you put a resistor in series with the LED?
Do you have some reason to think that the LED will run on 5 volts without a
series resistor?

I noticed that you did NOT say that the computer stopped working so I
assumed that the computer works fine, the power light just goes out. Is
that correct?




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

Yes, the computer works fine other than the power LED going out. I
didn't install a resistor, but there is one on the amp board. As for
the motherboard, I don't see a resistor, just lots of IC's.
Bryan

wrote in news:47b0133c-3b6f-4e48-9f2f-012830e9fc04
@p25g2000hsf.googlegroups.com:

Yes, the computer works fine other than the power LED going out. I
didn't install a resistor, but there is one on the amp board. As for
the motherboard, I don't see a resistor, just lots of IC's.
Bryan


I don't know what kind of assortment of LEDs you bought. MOST LEDs are
simply light emitting diodes without anything built in to limit the current
through the LED.
I would expect one to get very hot when hooked from 5 V directly to ground.
I would normally expect this to only happen once, as the diode burns out or
shorts.

The voltage that the LED requires depends on its construction which depends
on the color.

Do you have any rating information on the LED you tried to use?

Try putting a resistor in series with your LED. Try 100 ohms. See if the
LED stays lit longer.
If it doesn't light at all, try a lower value resistor. If it lights, stays
lit longer but still goes out, try a larger value resistor.

Have you tried another LED yet?


--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

I'm going to lecture the OP.

I assume the LED is self-installed -- you attached it to a B+ point (yes, I
know MOBOs use multiple voltages) for a visual indication that power was on.

Now you find that, no matter where you connect the LED, it goes off after
about 20 minutes. Assuming the computer is still running, that pretty much
eliminates the computer as the source of the problem. And assuming your
wiring isn't flaky (that is, it "opens" or comes loose after a period of
time), that leaves the LED.

So why didn't you replace the LED before asking for advice?

A different LED did the trick! It's working now. One of the problems
with those Radio Shack "grab bags" like I bought is there's no
information about the brightness or any of the other ratings.
Bryan

wrote in news:6e1bf52d-e0c6-4f11-8a63-
:

A different LED did the trick! It's working now. One of the problems
with those Radio Shack "grab bags" like I bought is there's no
information about the brightness or any of the other ratings.

Congratulations. I trust it has been an enlightening experience.



--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On 3ÔÂ31ÈÕ, ÉÏÎç1ʱ47·Ö, wrote:
A couple months ago I built myself a new computer and for some reason,
the power indicator LED stays on for about 20 seconds (when I first
turn the computer on). After that, it flickers and goes out. I've
hooked it up to 3 different locations on the motherboard and the
results have all been the same. What could be causing the LED to go
out?
Bryan



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On Sun, 30 Mar 2008 14:53:39 -0700, "William Sommerwerck"
wrote:


So why didn't you replace the LED before asking for advice?


Uh, because he couldn't believe a radio sludge LED would not work
right? Maybe?

I assumed it couldn't have been the LED because it was brand new.
Wrong again.
Bryan

On Mon, 31 Mar 2008 09:51:16 -0700 (PDT), wrote:

I assumed it couldn't have been the LED because it was brand new.
Wrong again.
Bryan

See, a more experienced person would have assumed that because it was
new from RS that it probably was defective! bg

On Mar 31, 2:22�pm, PeterD wrote:
See, a more experienced person would have assumed that because it was
new from RS that it probably was defective! bg

Don't even get me started. I needed a couple of RCA jacks for my
speakers and they had no idea what I was talking about! The only thing
their help seems to know anything about is cell phones. Of course, it
doesn't matter where you go anymore, it's the same BS everywhere. If
you know how to tie your shoe they'll hire you (speaking English is
optional).
Bryan

"PeterD" wrote in message
...
On Mon, 31 Mar 2008 09:51:16 -0700 (PDT),
wrote:

I assumed it couldn't have been the LED because it was brand new.
Wrong again.

See, a more experienced person would have assumed that
because it was new from RS that it probably was defective! bg

The issue isn't the source of the LED, it's rather that all the evidence
strongly pointed to it being the LED.