Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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  #1   Report Post  
Al
 
Posts: n/a
Default pc power supply failure?

Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in
fall of '91. The Power Supply is SFX, Gateway's part# is 6500545, 90W.
(AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days of
that behavior, it would then start only for a moment, and only with a few
spins of the ps fan (there is no CPU fan). Pushing the start button again
would have no effect - unless I removed the power cord and let it sit for
a minute or two. Then I'd replug and the pattern would repeat, with only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between pins 3
and 9, which should have given 5V.) When I removed all drives and tried
again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I blew
out. (Nothing looked burnt, that I could see.) But thereafter, the
computer behaved differently: when I merely plugged the power cord in,
I'd get the momentary light and ps fan spinning. It didn't need me to
actually push the power button anymore. Next, to see if the power on
switch might be shorted, I removed its leads from the MB - but that
didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU, the
MB or some other thing is bad, not the power supply? The more I research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device has
exceeded the current limits of its hub port". And a USB attachment for an
MP3 player had been added after Christmas. But the "current exceeded" msg
still sometimes appeared, even after the MP3 attachment had been removed.
  #2   Report Post  
Kevin R
 
Posts: n/a
Default

you can test the psu by shorting out (IIRC) the green cable to earth this
should power up the PSU and on my MB with out the cpu plugged in the psu
will power up

http://www.fonerbooks.com/power.htm has some diags on it
"Al" wrote in message
. ..
Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in
fall of '91. The Power Supply is SFX, Gateway's part# is 6500545, 90W.
(AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days of
that behavior, it would then start only for a moment, and only with a few
spins of the ps fan (there is no CPU fan). Pushing the start button again
would have no effect - unless I removed the power cord and let it sit for
a minute or two. Then I'd replug and the pattern would repeat, with only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between pins 3
and 9, which should have given 5V.) When I removed all drives and tried
again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I blew
out. (Nothing looked burnt, that I could see.) But thereafter, the
computer behaved differently: when I merely plugged the power cord in,
I'd get the momentary light and ps fan spinning. It didn't need me to
actually push the power button anymore. Next, to see if the power on
switch might be shorted, I removed its leads from the MB - but that
didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU, the
MB or some other thing is bad, not the power supply? The more I research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device has
exceeded the current limits of its hub port". And a USB attachment for an
MP3 player had been added after Christmas. But the "current exceeded" msg
still sometimes appeared, even after the MP3 attachment had been removed.



  #3   Report Post  
T i m
 
Posts: n/a
Default

On Fri, 21 Jan 2005 23:23:06 GMT, Al wrote:


I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.


I didn't spot that you had tested the PSU on the bench? If you plug in
the power then short PS (Pin14) on back to one of the (black?) common
wires (say Pin15) with a straight paper clip?

Like this . ..

http://www.duxcw.com/faq/ps/ps4.htm

If it runs up than it may either being overloaded by something within
the PC or simply faulty .. ?

All the best ..

T i m


  #4   Report Post  
Jerry G.
 
Posts: n/a
Default

The only proper way to test the power supply is to try it in another working
computer, or verify it by trying another one. The only other way is to bench
run it. I cannot remember for your supply how to start it without being
connected to the computer. When bench running it, it has to be properly
loaded. An unloaded power supply test is not viable, because they may fail
under load, and read normal with no load.

Most of the time, the failed components are not visible under inspection.
Proper troubleshooting must be done in order to determine the defective
parts.

Considering the low cost of a power supply, it is not a viable thing to
service.

--

Jerry G.
=====

"Al" wrote in message
. ..
Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in
fall of '91. The Power Supply is SFX, Gateway's part# is 6500545, 90W.
(AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days of
that behavior, it would then start only for a moment, and only with a few
spins of the ps fan (there is no CPU fan). Pushing the start button again
would have no effect - unless I removed the power cord and let it sit for
a minute or two. Then I'd replug and the pattern would repeat, with only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between pins 3
and 9, which should have given 5V.) When I removed all drives and tried
again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I blew
out. (Nothing looked burnt, that I could see.) But thereafter, the
computer behaved differently: when I merely plugged the power cord in,
I'd get the momentary light and ps fan spinning. It didn't need me to
actually push the power button anymore. Next, to see if the power on
switch might be shorted, I removed its leads from the MB - but that
didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU, the
MB or some other thing is bad, not the power supply? The more I research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device has
exceeded the current limits of its hub port". And a USB attachment for an
MP3 player had been added after Christmas. But the "current exceeded" msg
still sometimes appeared, even after the MP3 attachment had been removed.


  #5   Report Post  
TCS
 
Posts: n/a
Default

On Fri, 21 Jan 2005 23:47:03 GMT, T i m wrote:
On Fri, 21 Jan 2005 23:23:06 GMT, Al wrote:



I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.


I didn't spot that you had tested the PSU on the bench? If you plug in
the power then short PS (Pin14) on back to one of the (black?) common
wires (say Pin15) with a straight paper clip?


Like this . ..


http://www.duxcw.com/faq/ps/ps4.htm


If it runs up than it may either being overloaded by something within
the PC or simply faulty .. ?


It isn't enough that the power supply turns on.
There has to be standby voltage to the motherboard, and when
it's on, the pwr-ok has to be on as well as good 3.3, 5,
12V, and perhaps -12V outputs.




  #6   Report Post  
DaveM
 
Posts: n/a
Default

"Al" wrote in message
. ..
Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in
fall of '91. The Power Supply is SFX, Gateway's part# is 6500545, 90W.
(AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days of
that behavior, it would then start only for a moment, and only with a few
spins of the ps fan (there is no CPU fan). Pushing the start button again
would have no effect - unless I removed the power cord and let it sit for
a minute or two. Then I'd replug and the pattern would repeat, with only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between pins 3
and 9, which should have given 5V.) When I removed all drives and tried
again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I blew
out. (Nothing looked burnt, that I could see.) But thereafter, the
computer behaved differently: when I merely plugged the power cord in,
I'd get the momentary light and ps fan spinning. It didn't need me to
actually push the power button anymore. Next, to see if the power on
switch might be shorted, I removed its leads from the MB - but that
didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU, the
MB or some other thing is bad, not the power supply? The more I research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device has
exceeded the current limits of its hub port". And a USB attachment for an
MP3 player had been added after Christmas. But the "current exceeded" msg
still sometimes appeared, even after the MP3 attachment had been removed.


Check the 5V Standby output of the PSU on pin 9 of the connector (that will
be the green wire) with the PSU unplugged from the motherboard. If that
voltage is not present, your power supply is bad. That's the power to the
motherboard that powers the Wake-On-xxx circuitry in the computer. If it's
not there, there's no way for the motherboard to tell the PSU to go to full
power.

If that voltage is present, use a pice of hookup wire or a paper clip bent
into a "U" shape to temporarily short pin 14 on the connector to either
adjacent pin (pin 13 or pin 15). That simulates the motherboard signal to
go full power. If that desn't turn the power supply on, then the PSU is
bad.

If the 5V Standby voltage is present, but the motherboard doesn't turn the
PSU on, then the motherboard is likely bad. Don't forget the power switch
on the front of the computer. Be sure to check that with your ohmmeter.

--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!


  #7   Report Post  
 
Posts: n/a
Default


Al wrote:

Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in fall
of '91. The Power Supply is SFX, Gateway's part# is 6500545,
90W. (AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the


power indicator being always yellow, never green). After a few days

of
that behavior, it would then start only for a moment, and only with a

few
spins of the ps fan (there is no CPU fan). Pushing the start button

again
would have no effect - unless I removed the power cord and let it sit

for
a minute or two. Then I'd replug and the pattern would repeat, with

only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between

pins 3
and 9, which should have given 5V.)


It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU,

the
MB or some other thing is bad, not the power supply? The more I

research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the

week
or more it would take to be shipped to me, if it's not likely to be a

PSU
failure. How can I tell if the PSU is bad or not? Thanks.


The Power_Good_ signal is an output, not an input, but the Power_On
signal is an input, and if the Gateway/Newton is wired like standard
ATX it's pin 14 (green wire), activated by grounding it.

I'd first work on getting the 5V on pin 9 to work. It runs from either
the main power oscillator or has its own oscillator.

  #8   Report Post  
DaveM
 
Posts: n/a
Default

wrote in message
oups.com...

Al wrote:

Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in fall
of '91. The Power Supply is SFX, Gateway's part# is 6500545,
90W. (AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the


power indicator being always yellow, never green). After a few days

of
that behavior, it would then start only for a moment, and only with a

few
spins of the ps fan (there is no CPU fan). Pushing the start button

again
would have no effect - unless I removed the power cord and let it sit

for
a minute or two. Then I'd replug and the pattern would repeat, with

only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between

pins 3
and 9, which should have given 5V.)


It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU,

the
MB or some other thing is bad, not the power supply? The more I

research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the

week
or more it would take to be shipped to me, if it's not likely to be a

PSU
failure. How can I tell if the PSU is bad or not? Thanks.


The Power_Good_ signal is an output, not an input, but the Power_On
signal is an input, and if the Gateway/Newton is wired like standard
ATX it's pin 14 (green wire), activated by grounding it.

I'd first work on getting the 5V on pin 9 to work. It runs from either
the main power oscillator or has its own oscillator.



The 5V Standby supply is usually run from a small transformer supply or a
small switcher.. it can't be run from the main supply, otherwise full
power would be on constantly. 5V Standby is separate from the main supply
circuitry.


--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!


  #9   Report Post  
w_tom
 
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Default

CPU is not involved with your circuit. When power switch is
pressed, then power supply controller orders power supply on -
equivalent to what that paper clip does on the bench. Then
power supply has a limited time to get 3.3, 5, and 12 volts
turned on. If not, the power supply itself detects what it
believes is a shorted output - and shuts down all other
outputs.

With a meter, identify which output is shorted while others
would rise up before the power supply shuts them all down.

I believer pin 9 is the purple wire? Circuits that control
that 'paper clip' needs 5 volts always. If too low, then
numerous and strange problems will occur. Why a digital
multimeter? Is that purple wire above 4.88 volts? Only the
most expensive analog meters can measure 5 volts that
accurately.

You have properly described the functions of Power Good.
But Power Good tells CPU nothing. During power up, well,
strum you lips. This is what the CPU is doing during power
up. CPU does not yet have enough 'intellect' to control power
supply.

By far, a fastest way to determine power supply integrity is
to leave it inside the computer. If voltages don't come up,
suspect either too much load, shorted power lead, or defective
output from power supply. But then the meter will make it
apparent which voltage is having such problem. That voltage
will never rise up to value before power supply sees the
problem and shuts down other good voltages. This, of course
assumes the power supply controller is telling all three
essential voltages to power on. If no voltages rise, then
power supply controller and related circuits are now suspect.

Notice still no reason to remove supply or do bench testing.

One final point. If looking at $40 power supplies, then you
expect more problems. Minimally acceptable power supplies
start at about $60 retail. Those cheap power supplies sell
at lower price by forgetting to include essential functions.

Al wrote:
Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg
date in fall of '91. The Power Supply is SFX, Gateway's part# is
6500545, 90W. (AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days
of that behavior, it would then start only for a moment, and only
with a few spins of the ps fan (there is no CPU fan). Pushing the
start button again would have no effect - unless I removed the power
cord and let it sit for a minute or two. Then I'd replug and the
pattern would repeat, with only a momentary start for the first
button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between
pins 3 and 9, which should have given 5V.) When I removed all drives
and tried again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I
blew out. (Nothing looked burnt, that I could see.) But thereafter,
the computer behaved differently: when I merely plugged the power
cord in, I'd get the momentary light and ps fan spinning. It
didn't need me to actually push the power button anymore. Next, to
see if the power on switch might be shorted, I removed its leads
from the MB - but that didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU,
the MB or some other thing is bad, not the power supply? The more
I research on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the
week or more it would take to be shipped to me, if it's not likely
to be a PSU failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device
has exceeded the current limits of its hub port". And a USB attachment
for an MP3 player had been added after Christmas. But the "current
exceeded" msg still sometimes appeared, even after the MP3 attachment
had been removed.

  #10   Report Post  
Heavy G
 
Posts: n/a
Default

you could also take the PS to a computer shop and have them test it for you.
they whould have the proper test tool to be able to tell if its your PS or
the MB thats bad. if youre lucky they wont charge you for it. usually it a
simple test.

better to find out if it is indeed the PS thats bad. a PS is way cheaper
than a new computer, and they are pretty much like parts on your car...
sooner later they are meant ot fail and must be replaced as needed.





"Al" wrote in message
. ..
Hi. This is on a Gateway Essential, 950 Mhz Celeron, FlexATX, mfg date in
fall of '91. The Power Supply is SFX, Gateway's part# is 6500545, 90W.
(AKA Newton NPS-145PB-117 A Rev 03).

The computer would start but then go only into standby mode (with the
power indicator being always yellow, never green). After a few days of
that behavior, it would then start only for a moment, and only with a few
spins of the ps fan (there is no CPU fan). Pushing the start button again
would have no effect - unless I removed the power cord and let it sit for
a minute or two. Then I'd replug and the pattern would repeat, with only
a momentary start for the first button press.

With an analog voltmeter, I would see 1V for that brief moment, on
POWER_GOOD (pin 8). (I got the exact same result measuring between pins 3
and 9, which should have given 5V.) When I removed all drives and tried
again, I got the same behavior.

So, I took out and opened up the PSU. There was some dust, which I blew
out. (Nothing looked burnt, that I could see.) But thereafter, the
computer behaved differently: when I merely plugged the power cord in,
I'd get the momentary light and ps fan spinning. It didn't need me to
actually push the power button anymore. Next, to see if the power on
switch might be shorted, I removed its leads from the MB - but that
didn't change anything.

It seems to me that maybe the CPU is not getting a good signal on
POWER_GOOD, and so shuts down the PSU. Or could it be that the CPU, the
MB or some other thing is bad, not the power supply? The more I research
on this, the more it goes round and round.

I'd rather not waste $40-50 on trying a new PSU, not to mention the week
or more it would take to be shipped to me, if it's not likely to be a PSU
failure. How can I tell if the PSU is bad or not? Thanks.

Oh, and one more thing: weird behavior showed up in the last few weeks,
like the mouse and/or keyboard or even drives not showing up on POST.
This msg would also sometimes be given by Windows: "An unknown device has
exceeded the current limits of its hub port". And a USB attachment for an
MP3 player had been added after Christmas. But the "current exceeded" msg
still sometimes appeared, even after the MP3 attachment had been removed.



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