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Dell PC blinking yellow



 
 
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  #1  
Old August 1st 19, 09:39 PM posted to alt.comp.hardware.pc-homebuilt
RainbowMan
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Default Dell PC blinking yellow


Dell Optiplex 755 is not boot up and flashing yellow only not power go through MB. Google search is all saying there is problem either on PSU and the mother board. I connected other PSU on Dell and found no problem and I am using that PSU on Dell PC now. I also connected the Dell PSU on other computer and found no problem either. So basically Dell PSU and MB are Ok. Why the Dell PSU is not only working on Dell PC?
  #2  
Old August 2nd 19, 06:43 AM posted to alt.comp.hardware.pc-homebuilt
Banders
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Posts: 2
Default Dell PC blinking yellow

On 08/01/2019 01:39 PM, RainbowMan wrote:

Dell Optiplex 755 is not boot up and flashing yellow only not power go through MB. Google search is all saying there is problem either on PSU and the mother board. I connected other PSU on Dell and found no problem and I am using that PSU on Dell PC now. I also connected the Dell PSU on other computer and found no problem either. So basically Dell PSU and MB are Ok. Why the Dell PSU is not only working on Dell PC?


https://duckduckgo.com/?q=optiplex+b...ight&ia=videos

I followed this link
https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only
because it specifically mentioned 755.

I'm not going to watch the video because I don't have a Dell, don't want
to ever have one, Dell sucks, F*CK DELL.
  #3  
Old August 2nd 19, 07:34 AM posted to alt.comp.hardware.pc-homebuilt
T. Ment
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Posts: 86
Default Dell PC blinking yellow

On Thu, 1 Aug 2019 22:43:56 -0700, Banders wrote:

I followed this link
https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only
because it specifically mentioned 755.


I'm not going to watch the video because I don't have a Dell, don't want
to ever have one,


I don't have one either but I was curious. He performed witchcraft with
the power supply wires. Scary.

Dell likes to make non standard changes to standard things like the ATX
power connector. Maybe they wanted to be proprietary like IBM mainframes
back in the 70s.

That strategy helped IBM corner the mainframe market, but drove them out
of the PC market. Too bad Dell didn't learn the lesson.


  #4  
Old August 2nd 19, 03:53 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_26_]
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Posts: 1,109
Default Dell PC blinking yellow

T. Ment wrote:
On Thu, 1 Aug 2019 22:43:56 -0700, Banders wrote:

I followed this link
https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only
because it specifically mentioned 755.


I'm not going to watch the video because I don't have a Dell, don't want
to ever have one,


I don't have one either but I was curious. He performed witchcraft with
the power supply wires. Scary.

Dell likes to make non standard changes to standard things like the ATX
power connector. Maybe they wanted to be proprietary like IBM mainframes
back in the 70s.

That strategy helped IBM corner the mainframe market, but drove them out
of the PC market. Too bad Dell didn't learn the lesson.



Dell only used non-standard ATX wiring for a couple
of years. They switched back to standard after that.

The video referenced, is a horrible idea.

The dude is playing with PS_ON# , that's an input
to the PSU, and is a "level". You ground PS_ON# for
as long as you want the PSU to run and the fans to turn.

The computer has a button on the front. It is a normally
open, momentary contact, push button. When you depress the
switch for a fraction of a second, one of the "edges" of
the pulse signal causes the logic on the motherboard to
"latch" the pulse and present a "constant level"
on the PS_ON# signal. That's the green wire.

This stuff is all detailed in the ATX spec, of which
there are three versions, and this picture is from
the newest version. The newest version, with 24 pins,
was created to suit the PCI Express era and the need
for a bit extra +12V current. And that's carried on
a yellow wire in the four pin section added to the
connector.

https://i.postimg.cc/4xY5d4XK/standa...-pin-power.gif

*******

This does not explain why the light is flashing on
the front panel.

Front panel LEDs can use one or two-color LEDs.

The front panel LED flashes when the computer is
asleep. On older computers, the steady level on the
LED might be a red LED, and when the computer is
sleeping, that red LED blinks once per second.

You can, however, use a two-color LED, two wires,
and two GPIO signals to control it. For example,
a green-yellow LED.

GPIO_0 ----+----+ GPIO_0 GPIO_1
| |
--- --- 0V 0V (no light)
green \ / /\ yellow 5V 0V green
--- --- 0V 5V yellow
| | 5V 5V (no light)
GPIO_1 ----+----+

This makes it possible for a two wire pair,
running from two GPIO signals, to run one
bi-color LED. And make two colors of light.

If GPIO_0 is held at 0 volts, you can "flash"
a 5V signal on GPIO_1 and make a "flashing yellow"
light.

*******

Well, this is great and all, but the mystery part is:

"What feature of a Dell power supply is different
enough, to flash the front panel at startup?"

I don't know the answer to that. There was at least one
Dell model, where the power supply itself had a LED
on the back, and it was a "self-test" LED. It was
never clear what the self-test was doing. If that supply
was bad, it would light the LED on the back.

The supply has the "PWR_OK" signal, which is
supposed to assert when all levels are "close
to full value". When the 12V signal is 11V or greater,
that would be a good time to show "PWR_OK". That
typically happens about 35 milliseconds after
PS_ON# is asserted to the supply.

Now, is there an additional signal from the power supply ?

Is the additional signal carried on a separate wire pair ?

Dunno.

These are things a clever repair person would be looking
for. Differences. Differences between "bog standard"
and "what Dell has done".

But the grossly wrong wiring pattern (wires moved around
on the 20 pin nylon shell), that was a few years before
the Optiplex 755. And if you miss that, plugging in
the wrong supply, can ruin stuff.

If this is a self-test feature, then there needs to be
a means to get the intelligence from the supply to the
motherboard (or directly to the front panel LED). All the pins
on the main connector have a function, so Dell can't really
hijack them for fun.

Paul
  #5  
Old August 3rd 19, 06:19 AM posted to alt.comp.hardware.pc-homebuilt
RainbowMan
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Posts: 2
Default Dell PC blinking yellow


I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem.
Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected.
  #6  
Old August 3rd 19, 07:08 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_26_]
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Posts: 1,109
Default Dell PC blinking yellow

RainbowMan wrote:
I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem.
Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected.


On SATA, the 3.3V rail hardly matters.

Both SATA and IDE drives of the 3.5" variety, use
5V and 12V on the SATA. At 2.5", 5V alone is usually
sufficient for the task (even on SSDs).

3.3V is used on some SSDs with microSATA connectors,
which is a case where you'd want the 3.3V to be present.
I have not seen a reference to such things for some
time, and suspect they disappeared from the market.

And there is one other case where the 3.3V is important.
PWDIS.

https://web.archive.org/web/20181223...isable-pin.pdf

"There is a simple fix if you find yourself in a situation
where an Ultrastar SATA HDD is not spinning up.

By using a simple “Molex to SATA” power (no 3.3V power...)
connector (Figure 1) to supply power to the HDD, you can usually
eliminate the problem. Changing the power connector effectively
removes power from P3 (Pin 3) and allows the drive to spin up
normally."

A pinout listing PWDIS is shown here. I think Pin 11
can drive a LED, as an activity indicator, but I've not
heard of anyone hacking that and proving that all drives
have that capability.

https://pinoutguide.com/Power/sata-power_pinout.shtml

Paul
  #7  
Old August 3rd 19, 10:58 AM posted to alt.comp.hardware.pc-homebuilt
wasbit[_4_]
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Posts: 13
Default Dell PC blinking yellow

"RainbowMan" wrote in message
...

I reset the bios and reflush Dell the PSU and MB( because some voltage
still left over even though I completely turned off the system as some
online user recommend) and tried again it was working again. I thought I
fixed finally but the next morning I turned on again this time it is
completely dead. But the PSU still ok and the MB is ok too. I am using
24-pin other PSU and no problem.
Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since
this PSU only has 2 SATA cable) and the strange thing is Windows reported
SATA drive as PATA drive I guess since the 3.3V orange wire is
unconnected.


I read, a long time ago, that holding the power button in after isolating
the power, drains the charge in the capacitors.
Whether this is true, I don't know, but I've done it ever since.

--
Regards
wasbit

  #8  
Old August 3rd 19, 03:35 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_26_]
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Posts: 1,109
Default Dell PC blinking yellow

wasbit wrote:
"RainbowMan" wrote in message
...

I reset the bios and reflush Dell the PSU and MB( because some
voltage still left over even though I completely turned off the system
as some online user recommend) and tried again it was working again. I
thought I fixed finally but the next morning I turned on again this
time it is completely dead. But the PSU still ok and the MB is ok
too. I am using 24-pin other PSU and no problem.
Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA
(since this PSU only has 2 SATA cable) and the strange thing is
Windows reported SATA drive as PATA drive I guess since the 3.3V
orange wire is unconnected.


I read, a long time ago, that holding the power button in after
isolating the power, drains the charge in the capacitors.
Whether this is true, I don't know, but I've done it ever since.


The power drains on its own too.

It depends on which "edge" of the power signal
which is latched, as to when the draining occurs.

5---------------------
\ +5VSB voltage
0 \

----+ +---------
| | \ Front panel button
+------+ \ (low is active)

-----------+
| PS_ON# (low is active)
+-----------xxxx no-drive when no-5VSB
starts to drain

There are two converters running off a common 300V+ capacitor.

The +5VSB converter is always running when
the switch at the back is on.

After about 30 seconds, the +5VSB drains on its own
when there is a loss of AC.

Pressing the front panel switch and releasing,
starts the main converter running. It cannot
run for too long, since the caps have limited
holdup time (16msec maybe at full load).

The main converter may die out first, as at
some point there isn't enough 300V+ left
to operate it.

Or, the PS_ON# transistor may lack the ability
to keep PS_ON# at zero volts.

The +5VSB is probably the last one to wink out.

This changes the +5VSB discharge time from 30 seconds
to a couple seconds.

Since no active element clamps 3.3,5,12V outputs,
we can't say with certainty what residual voltage
is present. The VCore motherboard converter would
tend to drain +12V to maybe +6V. The VCore converter
does not run all the way down to zero volts.

The informal evidence, is the secondary outputs
drop to zero pretty well, without needing any
additional help from users.

So while pressing the button accelerates the
process a bit, in the end the result is about
the same. You save about 28 seconds of the
sequence.

On Asus motherboards, a green LED on the motherboard
is tied to +5VSB. When that LED goes out, it is
safe to work on the PC inside. Other brands
do not have this. For the brands that do not
have this, pressing the button reduces
the wait time, but the multimeter is
your best bet for determine +5VSB is gone.

There is a schematic showing the two halves of a
supply, here. But this does not show the motherboard
logic that controls PS_ON#. PS_ON# comes in around
the middle-left of the schematic.

http://www.pavouk.org/hw/en_atxps.html

Paul
  #9  
Old August 6th 19, 01:24 PM posted to alt.comp.hardware.pc-homebuilt
[email protected]
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Posts: 183
Default Dell PC blinking yellow

On Friday, August 2, 2019 at 2:34:53 PM UTC+8, T. Ment wrote:

Dell likes to make non standard changes to standard things like the ATX
power connector. Maybe they wanted to be proprietary like IBM mainframes
back in the 70s.

That strategy helped IBM corner the mainframe market, but drove them out
of the PC market. Too bad Dell didn't learn the lesson.


Not just Dell, I have a couple of HP Prodesk SFF PCs. Haswell i7, so still
adequate for lots of stuff. Unfortuately non-standard power supplies.
If they die, then they will be tossed onto dung-heap.
 




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