I'm servicing a Gateway GM5260. It uses an Intel DP965LV motherboard and it
has Windows XP installed. It also has this habit of freezing randomly. Then
you are forced to hold in the power button to shut it off. Here is the
interesting part. When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If you restart
it second time, usually it will power up fine. Occasionally, it will take a
third try to keep the power on. If the computer goes through a normal shut
down, the power up process always works the first time. I've swapped the
RAM, video card, and power supply, and it made no difference. The only
hardware issue I can find is that in the system bios, there is a value in
the hardware monitor called, +1.5V and it hovers around 1.298V. I have
inspected the caps and they don't look or test bad. The CPU and motherboard
temps are normal. Has anyone experienced this type of problem before?

Thanks for your replies.
--
David Farber
Los Osos, CA

On Wednesday, February 3, 2016 at 10:14:36 PM UTC-8, David Farber wrote:
I'm servicing a Gateway GM5260. It uses an Intel DP965LV motherboard and it
has Windows XP installed. It also has this habit of freezing randomly. Then
you are forced to hold in the power button to shut it off. Here is the
interesting part. When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If you restart
it second time, usually it will power up fine. Occasionally, it will take a
third try to keep the power on. If the computer goes through a normal shut
down, the power up process always works the first time. I've swapped the
RAM, video card, and power supply, and it made no difference. The only
hardware issue I can find is that in the system bios, there is a value in
the hardware monitor called, +1.5V and it hovers around 1.298V. I have
inspected the caps and they don't look or test bad. The CPU and motherboard
temps are normal. Has anyone experienced this type of problem before?

Thanks for your replies.
--
David Farber
Los Osos, CA

CAPS

On Wed, 3 Feb 2016 22:14:12 -0800, "David Farber"
wrote:

I'm servicing a Gateway GM5260. It uses an Intel DP965LV motherboard and it
has Windows XP installed. It also has this habit of freezing randomly. Then
you are forced to hold in the power button to shut it off. Here is the
interesting part. When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If you restart
it second time, usually it will power up fine. Occasionally, it will take a
third try to keep the power on. If the computer goes through a normal shut
down, the power up process always works the first time. I've swapped the
RAM, video card, and power supply, and it made no difference. The only
hardware issue I can find is that in the system bios, there is a value in
the hardware monitor called, +1.5V and it hovers around 1.298V. I have
inspected the caps and they don't look or test bad. The CPU and motherboard
temps are normal. Has anyone experienced this type of problem before?

Thanks for your replies.

Your description sounds exactly like the usual bulging capacitor
problem on the motherboard or in the power supply. You said that you
checked (tested?) the motherboard caps, but did you check the power
supply caps? The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Incidentally, what's happening is that when cold, the ESR (equivalent
series resistance) of the electrolytic capacitors is rather high,
resulting in lots of ripple, lousy regulation, bad breath, circuit
malfunction, and other undesirable things. However, as the capacitor
gets warmed up by the ripple current or nearby hot components, the ESR
goes down allowing the sick capacitor to act like a good capacitor.
The computah will probably work reasonably well, as long as it stays
warm, but will revert to simulating a stubborn mule when it cools
down.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 09/02/16 04:24, Jeff Liebermann wrote:
On Wed, 3 Feb 2016 22:14:12 -0800, "David Farber"
wrote:

I'm servicing a Gateway GM5260. It uses an Intel DP965LV motherboard and it
has Windows XP installed. It also has this habit of freezing randomly. Then
you are forced to hold in the power button to shut it off. Here is the
interesting part. When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If you restart
it second time, usually it will power up fine. Occasionally, it will take a
third try to keep the power on. If the computer goes through a normal shut
down, the power up process always works the first time. I've swapped the
RAM, video card, and power supply, and it made no difference. The only
hardware issue I can find is that in the system bios, there is a value in
the hardware monitor called, +1.5V and it hovers around 1.298V. I have
inspected the caps and they don't look or test bad. The CPU and motherboard
temps are normal. Has anyone experienced this type of problem before?

Thanks for your replies.

Your description sounds exactly like the usual bulging capacitor
problem on the motherboard or in the power supply. You said that you
checked (tested?) the motherboard caps, but did you check the power
supply caps? The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Agree with the caps diagnosis, I'd also follow the +5V standby supply
into the board with a meter while changing power state.

However, the +1.5V line, is that the CPU voltage voltage? 1.298V looks
in the ballpark for the CPU in that unit.

--
Adrian C

On Tue, 9 Feb 2016 10:17:14 +0000, Adrian Caspersz
wrote:

On 09/02/16 04:24, Jeff Liebermann wrote:
The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Agree with the caps diagnosis, I'd also follow the +5V standby supply
into the board with a meter while changing power state.

However, the +1.5V line, is that the CPU voltage voltage? 1.298V looks
in the ballpark for the CPU in that unit.

Try watching what the ATX power good gray wire does on a working
computah. There's small delay between turning on the power and when
the line goes high. Normal operation is a logic high which means
roughly +5VDC. +1.5V is definitely out of spec. I would venture a
guess that it's really oscillation or pulsing on the power good line,
which happens to average out to about +1.5V on a DVM.

Having the measured +1.5v be similar to the CPU voltage is
coincidence. Recycling the above Wikipedia page:
The ATX specification defines the Power-Good signal as a
+5 volt (V) signal generated in the power supply when it
has passed its internal self-tests and the outputs have
stabilized. This normally takes between 0.1 and 0.5 seconds
after the power supply is switched on. The signal is then
sent to the motherboard, where it is received by the
processor timer chip that controls the reset line to the
processor.

Cheaper and/or lower quality power supplies do not follow
the ATX specification of a separate monitoring circuit;
they instead wire the power good output to one of the 5 V
lines. This means the processor will never reset given
bad power unless the 5 V line drops low enough to turn
off the trigger, which could be too low for proper
operation.

I guess the easiest test is to just replace the PS with a known good
PS and see what happens. Checking the PS with a PS tester is also
useful. I have a really old and crude one but am considering getting
something like one of these:
https://www.google.com/search?q=atx+power+supply+tester+lcd&tbm=isch

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Tue, 9 Feb 2016 10:17:14 +0000, Adrian Caspersz
wrote:

On 09/02/16 04:24, Jeff Liebermann wrote:
The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Agree with the caps diagnosis, I'd also follow the +5V standby supply
into the board with a meter while changing power state.

However, the +1.5V line, is that the CPU voltage voltage? 1.298V
looks in the ballpark for the CPU in that unit.

Try watching what the ATX power good gray wire does on a working
computah. There's small delay between turning on the power and when
the line goes high. Normal operation is a logic high which means
roughly +5VDC. +1.5V is definitely out of spec. I would venture a
guess that it's really oscillation or pulsing on the power good line,
which happens to average out to about +1.5V on a DVM.

Having the measured +1.5v be similar to the CPU voltage is
coincidence. Recycling the above Wikipedia page:
The ATX specification defines the Power-Good signal as a
+5 volt (V) signal generated in the power supply when it
has passed its internal self-tests and the outputs have
stabilized. This normally takes between 0.1 and 0.5 seconds
after the power supply is switched on. The signal is then
sent to the motherboard, where it is received by the
processor timer chip that controls the reset line to the
processor.

Cheaper and/or lower quality power supplies do not follow
the ATX specification of a separate monitoring circuit;
they instead wire the power good output to one of the 5 V
lines. This means the processor will never reset given
bad power unless the 5 V line drops low enough to turn
off the trigger, which could be too low for proper
operation.

I guess the easiest test is to just replace the PS with a known good
PS and see what happens. Checking the PS with a PS tester is also
useful. I have a really old and crude one but am considering getting
something like one of these:
https://www.google.com/search?q=atx+power+supply+tester+lcd&tbm=isch

Just to make sure we're talking about the same thing, I said:
"The only hardware issue I can find is that in the system bios, there is a
value in
the hardware monitor called, +1.5V and it hovers around 1.298V."
From what I understand, it's supposed to be 1.5V, not 5V.

I did swap the power supply with a working unit and the same thing happened.

I used an ESR tester to test the caps on the motherboard and power supply.
They were fine.

Finally, I noticed that during an anti-virus update, the computer froze up
again. I uninstalled the anti-virus software (Avast) and it hasn't locked up
since. A few days later I installed AVG, and it's still running fine. I also
disabled the EIST service in the bios but I'm not sure if that mattered at
all.
http://www.intel.com/content/www/us/...000005723.html

What I never did figure out was why it took two power button pushes to
restart the computer after a freeze up. It reminds me of what happens when
you first apply AC to a computer (before even hitting the power button) the
power will briefly come on and then shut off.

Thanks for your replies.
--
David Farber
Los Osos, CA

On Fri, 12 Feb 2016 20:20:32 -0800, "David Farber"
wrote:


Just to make sure we're talking about the same thing, I said:
"The only hardware issue I can find is that in the system bios, there is a
value in
the hardware monitor called, +1.5V and it hovers around 1.298V."
From what I understand, it's supposed to be 1.5V, not 5V.

That would be the +1.5v DDR3 RAM power supply voltage:
http://www.building-a-gaming-computer.com/images/hardware_monitor_screen.jpg
It should be very close to +1.5v.

I was referring to the voltage on the ATX power connector pin 8:
http://i.stack.imgur.com/VZS6f.jpg
as measured with a voltmeter.

I did swap the power supply with a working unit and the same thing happened.
I used an ESR tester to test the caps on the motherboard and power supply.
They were fine.

Oops. So much for these theories.

Finally, I noticed that during an anti-virus update, the computer froze up
again. I uninstalled the anti-virus software (Avast) and it hasn't locked up
since. A few days later I installed AVG, and it's still running fine. I also
disabled the EIST service in the bios but I'm not sure if that mattered at
all.
http://www.intel.com/content/www/us/...000005723.html

I'm having a difficult time believing that any program can produce a
power related boot failure BEFORE the OS is loaded. You mentioned:
"When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If
you restart it second time, usually it will power up fine.
Occasionally, it will take a third try to keep the power on."
That's all before the OS or auntie-virus is loaded. About the only
think I can conjure that might be involved is when the BIOS loads the
microcode updates into the CPU. Weird.

What I never did figure out was why it took two power button pushes to
restart the computer after a freeze up. It reminds me of what happens when
you first apply AC to a computer (before even hitting the power button) the
power will briefly come on and then shut off.

Will you please find a scope or voltmeter, attach it to Pin 8 (power
good) line of the ATX connector and see if there are any long delays,
oscillations, or complaints on this line that might inspire the
motherboard to shut down? Everything I read hear (except the
auntie-virus stuff) points to a power related problem. If the +1.5v
line is low, it might be defective RAM sucking excessive current from
the Vdd power line. Run a RAM test and see if you get it to fail.
http://www.memtest86.com
http://www.memtest.org (better)

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Friday, February 12, 2016 at 8:21:47 PM UTC-8, David Farber wrote:
Jeff Liebermann wrote:
On Tue, 9 Feb 2016 10:17:14 +0000, Adrian Caspersz
wrote:

On 09/02/16 04:24, Jeff Liebermann wrote:
The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Agree with the caps diagnosis, I'd also follow the +5V standby supply
into the board with a meter while changing power state.

However, the +1.5V line, is that the CPU voltage voltage? 1.298V
looks in the ballpark for the CPU in that unit.

Try watching what the ATX power good gray wire does on a working
computah. There's small delay between turning on the power and when
the line goes high. Normal operation is a logic high which means
roughly +5VDC. +1.5V is definitely out of spec. I would venture a
guess that it's really oscillation or pulsing on the power good line,
which happens to average out to about +1.5V on a DVM.

Having the measured +1.5v be similar to the CPU voltage is
coincidence. Recycling the above Wikipedia page:
The ATX specification defines the Power-Good signal as a
+5 volt (V) signal generated in the power supply when it
has passed its internal self-tests and the outputs have
stabilized. This normally takes between 0.1 and 0.5 seconds
after the power supply is switched on. The signal is then
sent to the motherboard, where it is received by the
processor timer chip that controls the reset line to the
processor.

Cheaper and/or lower quality power supplies do not follow
the ATX specification of a separate monitoring circuit;
they instead wire the power good output to one of the 5 V
lines. This means the processor will never reset given
bad power unless the 5 V line drops low enough to turn
off the trigger, which could be too low for proper
operation.

I guess the easiest test is to just replace the PS with a known good
PS and see what happens. Checking the PS with a PS tester is also
useful. I have a really old and crude one but am considering getting
something like one of these:
https://www.google.com/search?q=atx+power+supply+tester+lcd&tbm=isch

Just to make sure we're talking about the same thing, I said:
"The only hardware issue I can find is that in the system bios, there is a
value in
the hardware monitor called, +1.5V and it hovers around 1.298V."
From what I understand, it's supposed to be 1.5V, not 5V.

I did swap the power supply with a working unit and the same thing happened.

I used an ESR tester to test the caps on the motherboard and power supply..
They were fine.

Finally, I noticed that during an anti-virus update, the computer froze up
again. I uninstalled the anti-virus software (Avast) and it hasn't locked up
since. A few days later I installed AVG, and it's still running fine. I also
disabled the EIST service in the bios but I'm not sure if that mattered at
all.
http://www.intel.com/content/www/us/...000005723.html

What I never did figure out was why it took two power button pushes to
restart the computer after a freeze up. It reminds me of what happens when
you first apply AC to a computer (before even hitting the power button) the
power will briefly come on and then shut off.

Thanks for your replies.
--
David Farber
Los Osos, CA

ESR meters will not necessarily give a valid reading. SMPS need really good caps so an ESR reading of 'good' may not, in fact, be good enough. I was working on a PC power supply today only because it is used in a very special computer and the manufacture is phasing it out but our people intend to use them a few more years. One of the caps I pulled read nothing on the meter but when I probed the board where it was, the reading was 'good'.

Consider solid polymers if available. Otherwise I go for the highest ripple current and longest hours rating. THEN price comes in to the picture. My time is way more expensive than any capacitor I put in.

'Lytics on a motherboard over 5 years old are suspect and probably need to go.

G²

wrote:
On Friday, February 12, 2016 at 8:21:47 PM UTC-8, David Farber wrote:
Jeff Liebermann wrote:
On Tue, 9 Feb 2016 10:17:14 +0000, Adrian Caspersz
wrote:

On 09/02/16 04:24, Jeff Liebermann wrote:
The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal

Agree with the caps diagnosis, I'd also follow the +5V standby
supply into the board with a meter while changing power state.

However, the +1.5V line, is that the CPU voltage voltage? 1.298V
looks in the ballpark for the CPU in that unit.

Try watching what the ATX power good gray wire does on a working
computah. There's small delay between turning on the power and when
the line goes high. Normal operation is a logic high which means
roughly +5VDC. +1.5V is definitely out of spec. I would venture a
guess that it's really oscillation or pulsing on the power good
line, which happens to average out to about +1.5V on a DVM.

Having the measured +1.5v be similar to the CPU voltage is
coincidence. Recycling the above Wikipedia page:
The ATX specification defines the Power-Good signal as a
+5 volt (V) signal generated in the power supply when it
has passed its internal self-tests and the outputs have
stabilized. This normally takes between 0.1 and 0.5 seconds
after the power supply is switched on. The signal is then
sent to the motherboard, where it is received by the
processor timer chip that controls the reset line to the
processor.

Cheaper and/or lower quality power supplies do not follow
the ATX specification of a separate monitoring circuit;
they instead wire the power good output to one of the 5 V
lines. This means the processor will never reset given
bad power unless the 5 V line drops low enough to turn
off the trigger, which could be too low for proper
operation.

I guess the easiest test is to just replace the PS with a known good
PS and see what happens. Checking the PS with a PS tester is also
useful. I have a really old and crude one but am considering
getting something like one of these:
https://www.google.com/search?q=atx+power+supply+tester+lcd&tbm=isch

Just to make sure we're talking about the same thing, I said:
"The only hardware issue I can find is that in the system bios,
there is a value in
the hardware monitor called, +1.5V and it hovers around 1.29V."
From what I understand, it's supposed to be 1.5V, not 5V.

I did swap the power supply with a working unit and the same thing
happened.

I used an ESR tester to test the caps on the motherboard and power
supply. They were fine.

Finally, I noticed that during an anti-virus update, the computer
froze up again. I uninstalled the anti-virus software (Avast) and it
hasn't locked up since. A few days later I installed AVG, and it's
still running fine. I also disabled the EIST service in the bios but
I'm not sure if that mattered at all.
http://www.intel.com/content/www/us/...000005723.html

What I never did figure out was why it took two power button pushes
to restart the computer after a freeze up. It reminds me of what
happens when you first apply AC to a computer (before even hitting
the power button) the power will briefly come on and then shut off.

Thanks for your replies.
--
David Farber
Los Osos, CA

ESR meters will not necessarily give a valid reading. SMPS need
really good caps so an ESR reading of 'good' may not, in fact, be
good enough. I was working on a PC power supply today only because it
is used in a very special computer and the manufacture is phasing it
out but our people intend to use them a few more years. One of the
caps I pulled read nothing on the meter but when I probed the board
where it was, the reading was 'good'.

Consider solid polymers if available. Otherwise I go for the highest
ripple current and longest hours rating. THEN price comes in to the
picture. My time is way more expensive than any capacitor I put in.

'Lytics on a motherboard over 5 years old are suspect and probably
need to go.

G²

Hi G^2

All very good points. I ran into this situation a few years ago and got some
very good advice here.
https://groups.google.com/forum/#!search/farberbear$20esr$20motherboard$20caps/sci.electronics.repair/-INdlCsyeJI/TqPCHmynoEUJ

Most notably the fact that many of the caps are in parallel and the ESR
readings should be much lower than out of circuit.

However, I see this present situation as perhaps two different problems
which a

Is the freezing problem really only software related?

Is the power up glitch ONLY after a freeze up a flaw or a feature?
Even when cold in the morning, it starts up fine if the night before it
powered down normally.

I'll go ahead and check out Jeff's suggestion:

"Will you please find a scope or voltmeter, attach it to Pin 8 (power
good) line of the ATX connector and see if there are any long delays,
oscillations, or complaints on this line that might inspire the
motherboard to shut down? Everything I read hear (except the
auntie-virus stuff) points to a power related problem. If the +1.5v
line is low, it might be defective RAM sucking excessive current from
the Vdd power line. Run a RAM test and see if you get it to fail."

Message to Jeff:
What exactly should I see on my scope at Pin 8 and am I monitoring this
constantly or only when I power up the machine? Also note that I did swap
all four RAM sticks with new ones and the same thing happened (before I
changed AV programs).

Thanks for your replies.
--
David Farber
Los Osos, CA

On Sat, 13 Feb 2016 08:26:20 -0800, "David Farber"
wrote:

I'll go ahead and check out Jeff's suggestion:

"Will you please find a scope or voltmeter, attach it to Pin 8 (power
good) line of the ATX connector and see if there are any long delays,
oscillations, or complaints on this line that might inspire the
motherboard to shut down? Everything I read hear (except the
auntie-virus stuff) points to a power related problem. If the +1.5v
line is low, it might be defective RAM sucking excessive current from
the Vdd power line. Run a RAM test and see if you get it to fail."

Message to Jeff:
What exactly should I see on my scope at Pin 8 and am I monitoring this
constantly or only when I power up the machine? Also note that I did swap
all four RAM sticks with new ones and the same thing happened (before I
changed AV programs).

So much for the RAM idea.

The PS_OK line should start at 0v. When you turn on the power, it
should stay at zero for between 100 msec to 500 msec, when it should
suddenly rise to something near +5v. The length of time it takes to
rise, after the power is applied, is an indication of potential
problems. I'm not certain what is considered normal or typical but I
seem to recall about 300 msec. I trigger on the +5V to 0V PS_ON line
used to turn on the PS.

The fun starts when it's 0 msec, which indicates a cheap junk power
supply with no power good circuit. The line is simply tied to the +5V
power supply output line. That will create a boot failure or startup
hang because the CPU wants to see stable power supply voltages.

Longer times and strange oscillation are also problems. A PS with
bulging caps on the +5V line (quite common) will show either long
delays or 100KHz hash for a few msec until the caps warm up. I've
also seen the line go high for a while, then drop, and go high again,
which caused some odd startup failures. However, I didn't investigate
the cause and just recycled the PS.

http://www.pcguide.com/ref/power/sup/funcPowerGood-c.html
http://www.formfactors.org/developer/specs/PSU_DG_rev_1_1.pdf
http://www.formfactors.org/developer/specs/ATX12V%20PSDG2.01.pdf
Table 13. PWR_OK Signal Characteristics
Signal Type +5 V TTL compatible
Logic level low 0.4 V
Logic level high 2.4 V and 5 V
High-state output impedance 1 k? from output to common
PWR_OK delay 100 ms T3 500 ms
PWR_OK risetime T4 = 10 ms
AC loss to PWR_OK hold-up time T5 = 16 ms
Power-down warning T6 = 1 ms
There's more detail in Sect 3.3 (Pg 23).

Also, there's something else worth trying. The ATX power supply keeps
power applied to some parts of the motherboard when the computah is
turned off. Mostly, that's the ethernet and wireless cards which use
WoL (wake on LAN) to turn the computer on remotely. You note that
holding the power button down to shut off the computer causes the
computer to shut down about 1 second after turning it back on. Try:
1. Hold the button down, wait, and then turn it back on.
2. Hold the button down, pull the power plug, wait about 20 seconds
for everything to discharge, plug it back in, and turn it back on.
If magically pulling the plug stops the shutdown on startup oddity,
then methinks something might be odd with the WoL circuitry on the
motherboard.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Sat, 13 Feb 2016 08:26:20 -0800, "David Farber"
wrote:

I'll go ahead and check out Jeff's suggestion:

"Will you please find a scope or voltmeter, attach it to Pin 8 (power
good) line of the ATX connector and see if there are any long delays,
oscillations, or complaints on this line that might inspire the
motherboard to shut down? Everything I read hear (except the
auntie-virus stuff) points to a power related problem. If the +1.5v
line is low, it might be defective RAM sucking excessive current from
the Vdd power line. Run a RAM test and see if you get it to fail."

Message to Jeff:
What exactly should I see on my scope at Pin 8 and am I monitoring
this constantly or only when I power up the machine? Also note that
I did swap all four RAM sticks with new ones and the same thing
happened (before I changed AV programs).

So much for the RAM idea.

The PS_OK line should start at 0v. When you turn on the power, it
should stay at zero for between 100 msec to 500 msec, when it should
suddenly rise to something near +5v. The length of time it takes to
rise, after the power is applied, is an indication of potential
problems. I'm not certain what is considered normal or typical but I
seem to recall about 300 msec. I trigger on the +5V to 0V PS_ON line
used to turn on the PS.

The fun starts when it's 0 msec, which indicates a cheap junk power
supply with no power good circuit. The line is simply tied to the +5V
power supply output line. That will create a boot failure or startup
hang because the CPU wants to see stable power supply voltages.

Longer times and strange oscillation are also problems. A PS with
bulging caps on the +5V line (quite common) will show either long
delays or 100KHz hash for a few msec until the caps warm up. I've
also seen the line go high for a while, then drop, and go high again,
which caused some odd startup failures. However, I didn't investigate
the cause and just recycled the PS.

http://www.pcguide.com/ref/power/sup/funcPowerGood-c.html
http://www.formfactors.org/developer/specs/PSU_DG_rev_1_1.pdf
http://www.formfactors.org/developer/specs/ATX12V%20PSDG2.01.pdf
Table 13. PWR_OK Signal Characteristics
Signal Type +5 V TTL compatible
Logic level low 0.4 V
Logic level high 2.4 V and 5 V
High-state output impedance 1 k? from output to common
PWR_OK delay 100 ms T3 500 ms
PWR_OK risetime T4 = 10 ms
AC loss to PWR_OK hold-up time T5 = 16 ms
Power-down warning T6 = 1 ms
There's more detail in Sect 3.3 (Pg 23).

Also, there's something else worth trying. The ATX power supply keeps
power applied to some parts of the motherboard when the computah is
turned off. Mostly, that's the ethernet and wireless cards which use
WoL (wake on LAN) to turn the computer on remotely. You note that
holding the power button down to shut off the computer causes the
computer to shut down about 1 second after turning it back on. Try:
1. Hold the button down, wait, and then turn it back on.
2. Hold the button down, pull the power plug, wait about 20 seconds
for everything to discharge, plug it back in, and turn it back on.
If magically pulling the plug stops the shutdown on startup oddity,
then methinks something might be odd with the WoL circuitry on the
motherboard.

I know from experience with this computer, that unplugging it and then
plugging it back in again after a freeze up has no effect on the outcome. It
will be interesting to see what happens if it is powered off without a
freeze up. I would guess that it will still take two power up sequences to
keep it on.

How am I supposed to see the 10ms pulse rise time with an old Philips PM
3217, nonstorage-type scope and then also determine the delay time? (By the
way, I wouldn't mind having a newer scope if you have any suggestions.)

Thanks for your reply.
--
David Farber
Los Osos, CA

On Sat, 13 Feb 2016 14:39:51 -0800, "David Farber"
wrote:

How am I supposed to see the 10ms pulse rise time with an old Philips PM
3217, nonstorage-type scope and then also determine the delay time? (By the
way, I wouldn't mind having a newer scope if you have any suggestions.)

10 msec rise time requires only:
0.35 / 10 msec = 35 Hz bandwidth
http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/oscilloscopes/bandwidth-and-waveform-rise-time-relationship
Unless your Philips PM3217 has a problem, you should be able to see
that on any oscilloscope.

I have a fairly large collection of older oscilloscopes. Several are
promised as bribes to various people. I'll throw together a list and
email it to you. Shipping and packing is the major expense. The to
be repaired pile:
http://802.11junk.com/jeffl/crud/scopes-to-be-fixed.jpg
There are about twice as many scattered around the house and office.

If you're cheap, and only deal with 100KHz signals, there are some
really nifty DSO scope kits on eBay.
http://www.ebay.com/itm/281695266238
http://www.ebay.com/itm/381394300534
Or, if you don't need DC coupling, just use your PC sound card and
some softwa
http://www.sillanumsoft.org

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Sat, 13 Feb 2016 14:39:51 -0800, "David Farber"
wrote:

How am I supposed to see the 10ms pulse rise time with an old
Philips PM 3217, nonstorage-type scope and then also determine the
delay time? (By the way, I wouldn't mind having a newer scope if you
have any suggestions.)

10 msec rise time requires only:
0.35 / 10 msec = 35 Hz bandwidth
http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/oscilloscopes/bandwidth-and-waveform-rise-time-relationship
Unless your Philips PM3217 has a problem, you should be able to see
that on any oscilloscope.

I have a fairly large collection of older oscilloscopes. Several are
promised as bribes to various people. I'll throw together a list and
email it to you. Shipping and packing is the major expense. The to
be repaired pile:
http://802.11junk.com/jeffl/crud/scopes-to-be-fixed.jpg
There are about twice as many scattered around the house and office.

If you're cheap, and only deal with 100KHz signals, there are some
really nifty DSO scope kits on eBay.
http://www.ebay.com/itm/281695266238
http://www.ebay.com/itm/381394300534
Or, if you don't need DC coupling, just use your PC sound card and
some softwa
http://www.sillanumsoft.org

My concern is that since it's a transient pulse, that it will not be on the
screen long enough for me to see it unless you're saying that it might
oscillate continuously.

Thanks for your reply.
--
David Farber
Los Osos, CA

On Sun, 14 Feb 2016 14:47:06 -0800, "David Farber"
wrote:

My concern is that since it's a transient pulse, that it will not be on the
screen long enough for me to see it unless you're saying that it might
oscillate continuously.

If you trigger on the leading edge rising voltage and setup your scope
for single trace, it will probably be visible. However a DSO (digital
storage oscilloscope) will do better at capturing the pulse.

However, the rising edge is not as interesting as the time delay
between when you apply power, and when the PWR_OK line goes high. At
50 or 100 msec/div, you should have no problems seeing if there are
any oddities or excessive delays.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Sun, 14 Feb 2016 14:47:06 -0800, "David Farber"
wrote:

My concern is that since it's a transient pulse, that it will not be
on the screen long enough for me to see it unless you're saying that
it might oscillate continuously.

If you trigger on the leading edge rising voltage and setup your scope
for single trace, it will probably be visible. However a DSO (digital
storage oscilloscope) will do better at capturing the pulse.

However, the rising edge is not as interesting as the time delay
between when you apply power, and when the PWR_OK line goes high. At
50 or 100 msec/div, you should have no problems seeing if there are
any oddities or excessive delays.

Hi Jeff,

I checked out the delay pulse time on pin 8. It seemed normal although it
was hard to tell because a tenth of a second goes by rather quickly.

I did a test power off by pressing the power button while in the BIOS menu
and it shut down immediately. There was not even the slightest delay
compared to what happens when Windows freezes up. The next power up happened
on the first try. I did the same thing when booting to the command prompt.
Instant off on the power button press and then a restart on the first try. I
wonder if the motherboard is keeping track when you get a bad shutdown and
intentionally makes you press the power button twice.

Thanks for your reply.
--
David Farber
Los Osos, CA

On Tue, 1 Mar 2016 15:26:28 -0800, "David Farber"
wrote:

I checked out the delay pulse time on pin 8. It seemed normal although it
was hard to tell because a tenth of a second goes by rather quickly.

0.1sec is a long time with an oscilloscope. Beg, buy, or borrow one.
It helps. However, the power good line seems to be working if you
didn't see any inordinately long delays. That leaves noise, which
you're not going to see without an oscilloscope. As I previously
suggested, use a sound card PC software oscilloscope. (No, you cannot
run the PC scope software on the machine that you're trying to test).

I did a test power off by pressing the power button while in the BIOS menu
and it shut down immediately. There was not even the slightest delay
compared to what happens when Windows freezes up. The next power up happened
on the first try. I did the same thing when booting to the command prompt.
Instant off on the power button press and then a restart on the first try. I
wonder if the motherboard is keeping track when you get a bad shutdown and
intentionally makes you press the power button twice.

I don't know about hitting the button twice, but many BIOS's will do a
rather fast boot if you reboot, but take forever to test everything if
you reboot after a failed boot. I guess(tm) the previous boot status
is stored somewhere as long as AC power is applied. It's NOT in the
power supply.

Incidentally, I recently fixed a Dell Optiplex 760 SFF machine that
required pressing the power on/off button twice in order to get it to
do anything. I replaced the power supply for other reasons (bulging
caps) but that wasn't the cause. After some fumbling, it turned out
to be bad contacts in the switch. However, that doesn't sound like
anything that might produce the symptoms you're seeing.

When in doubt, replace everything.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Tue, 1 Mar 2016 15:26:28 -0800, "David Farber"
wrote:

I checked out the delay pulse time on pin 8. It seemed normal
although it was hard to tell because a tenth of a second goes by
rather quickly.

0.1sec is a long time with an oscilloscope. Beg, buy, or borrow one.
It helps. However, the power good line seems to be working if you
didn't see any inordinately long delays. That leaves noise, which
you're not going to see without an oscilloscope. As I previously
suggested, use a sound card PC software oscilloscope. (No, you cannot
run the PC scope software on the machine that you're trying to test).

I did a test power off by pressing the power button while in the
BIOS menu and it shut down immediately. There was not even the
slightest delay compared to what happens when Windows freezes up.
The next power up happened on the first try. I did the same thing
when booting to the command prompt. Instant off on the power button
press and then a restart on the first try. I wonder if the
motherboard is keeping track when you get a bad shutdown and
intentionally makes you press the power button twice.

I don't know about hitting the button twice, but many BIOS's will do a
rather fast boot if you reboot, but take forever to test everything if
you reboot after a failed boot. I guess(tm) the previous boot status
is stored somewhere as long as AC power is applied. It's NOT in the
power supply.

Incidentally, I recently fixed a Dell Optiplex 760 SFF machine that
required pressing the power on/off button twice in order to get it to
do anything. I replaced the power supply for other reasons (bulging
caps) but that wasn't the cause. After some fumbling, it turned out
to be bad contacts in the switch. However, that doesn't sound like
anything that might produce the symptoms you're seeing.

When in doubt, replace everything.

Hi Jeff,

Was I supposed to use one channel of the scope to monitor the power button
line and then monitor the PS_ON line with the other channel, and then see
the delay time between the two?

My customer picked up the unit quite a while ago and has had no
complaints... so far.

Thanks for your reply.
--
David Farber
Los Osos, CA