Which part's at fault?

  • Thread starter Thread starter saltbeet
  • Start date Start date
S

saltbeet

Sometimes when I push the power button to start my machine, nothing at
all happens. The power supply fan doesn't even turn. (The computer
is pulling 2 or 3 watts, though.) So far, I've been able to get it
started, eventually, by unplugging the power cord from the computer,
then plugging back in. The first time this happened, that made the
machine start right away, but this morning it took maybe 20 times.
The problem was rare to start with, is becoming more frequent, but
still happens only one time in 15 or so. I checked all connections
not long ago. There has never been a problem once I get it running.
I was going to put together a new system anyway, so this speeded
things up: I'm just waiting for one more component to arrive.

The problem's got to be in the power supply, power switch, or
motherboard, I figure, but given the intermittent nature, I don't know
how to proceed. I'm guessing motherboard, since it's cheap crap and I
can probably name 5 or 6 tolerable problems it has. I'll be tossing
that. If it's in the power supply, well, I've got a new one, but I'd
like to eBay the old one if I can do so in good conscience. If it's
in the power switch, I don't know---I'd like to reuse the case (Lian
Li), but I don't know if the switch is replaceable (and can't get a
look at it right now).

Any ideas about what's to blame? And if it's the switch, are they
standard, so that I'm likely to be able to find a replacement?

Thanks.
 
saltbeet said:
Sometimes when I push the power button to start my machine, nothing at
all happens. The power supply fan doesn't even turn. (The computer
is pulling 2 or 3 watts, though.) So far, I've been able to get it
started, eventually, by unplugging the power cord from the computer,
then plugging back in. The first time this happened, that made the
machine start right away, but this morning it took maybe 20 times.
The problem was rare to start with, is becoming more frequent, but
still happens only one time in 15 or so. I checked all connections
not long ago. There has never been a problem once I get it running.
I was going to put together a new system anyway, so this speeded
things up: I'm just waiting for one more component to arrive.

The problem's got to be in the power supply, power switch, or
motherboard, I figure, but given the intermittent nature, I don't know
how to proceed. I'm guessing motherboard, since it's cheap crap and I
can probably name 5 or 6 tolerable problems it has. I'll be tossing
that. If it's in the power supply, well, I've got a new one, but I'd
like to eBay the old one if I can do so in good conscience. If it's
in the power switch, I don't know---I'd like to reuse the case (Lian
Li), but I don't know if the switch is replaceable (and can't get a
look at it right now).

Any ideas about what's to blame? And if it's the switch, are they
standard, so that I'm likely to be able to find a replacement?

Thanks.
Click to expand...
Most likely is PSU. Is easy to test if you can beg/borrow a suitable PSU to
test with, just attach all the cables to the motherboard, no need to install
in case.
Mike.
 
I would assume that the PSU or the motherboard is at fault. Power switches
do not routinely fail. I would start your testing by replacing the PSU with
a known good quality working unit. (That's much easier than replacing the
motherboard as a first try.)
 
Sometimes when I push the power button to start my machine, nothing at
all happens. Thepower supplyfan doesn't even turn. (The computer
is pulling 2 or 3 watts, though.) So far, I've been able to get it
started, eventually, by unplugging the power cord from the computer,
then plugging back in. The first time this happened, that made the
machine start right away, but this morning it took maybe 20 times.
The problem was rare to start with, is becoming more frequent, but
still happens only one time in 15 or so.
Click to expand...

Intermittents are sometimes due to voltages that are completely
wrong. Two minutes with a 3.5 digit multimeter would tell more. There
is no "yes or no" voltage. There are numbers that should be reviewed
both before and when power switch is pressed. See the two minute
procedure in "When your computer dies without warning....." starting
6 Feb 2007 in the newsgroup alt.windows-xp at:
http://tinyurl.com/yvf9vh

Power supply controller is reset by removing power cord from AC
supply. If your problem is there, well, the meter may explain why -
especially from numbers for the purple wire and action of the green
and gray wire before and during powerup.
 
w_tom said:
Intermittents are sometimes due to voltages that are completely
wrong. Two minutes with a 3.5 digit multimeter would tell more.
There is no "yes or no" voltage. There are numbers that should be
reviewed both before and when power switch is pressed.
Click to expand...

The vast majority of users have no business probing around inside of a
computer when it is plugged into the wall, and especially not probing
the power supply.

As usual, w_tom is trying to spread bullshit that is potentially
hazardous to people and their property.
See the two minute procedure in "When your computer dies without
warning....." starting 6 Feb 2007 in the newsgroup alt.windows-xp
at:
Click to expand...

Better to do an author history on w_tom and "surge suppressor" if you
want to learn more about w_tom's idiotic rantings here on USENET.
 
The vast majority of users have no business probing around inside of a
computer when it is plugged into the wall, and especially not probing
the power supply.

As usual, w_tom is trying to spread bullshit that is potentially
hazardous to people and their property.


Better to do an author history on w_tom and "surge suppressor" if you
want to learn more about w_tom's idiotic rantings here on USENET.
Click to expand...

Thanks for the warning, and yes, I searched. Still, with the aid of
something I've tucked away somewhere from an online guide, I think I'm
going to give some exploration a shot. Once I get the SCSI drives and
card out of the case there's really not much in there I'm worried
about harming. And I won't be going in to the power supply itself.
I'll be careful.

Thanks, everybody.
 
Thanks for the warning, and yes, I searched. Still, with the
aid of something I've tucked away somewhere from an
online guide, I think I'm going to give some exploration a
shot. Once I get the SCSI drives and card out of the case
there's really not much in there I'm worried about harming.
And I won't be going in to the power supply itself.
Click to expand...

Nothing exposed in a computer that can harm you. Multimeter cannot
harm anything inside that computer. Two minutes with a simplest tool
will either identify the problem OR provide numbers so that others can
identify the problem. Those numbers are most useful when SCSI drive is
installed to consume power AND to boot the system. You must boot the
system to increase power consumption and better identify defects.

John Doe is doing what he always does because he was exposed many
times posting technical myths. He has simply done it again. John Doe
who has a long history of attacking people he does not like. He has a
history of posting without technical knowledge. To appreciate his
integrity, search on posts using the search terms "John Doe" and
"Mark Bender". John Doe has made many enemies; apparently takes glee
in perverting useful recommendations. His post to you is classic of
who John Doe is.

Note posts last May where he even asks how to measure energy and
other simple electric questions. Someone with basic electronics
knowledge would never ask those questions. John Doe attacks people;
not problems. His technical knowledge is that limited. His need to
take revenge that great.

Use the meter as described. Your problem is typically found in any
part of the power supply system. The power supply is only one suspect
of a power supply system. Intermittents as you have described are
often obvious in numbers from that meter even when the system does not
boot. Remove or disconnect nothing. The meter reports most useful
information when everything remains undisturbed inside the computer.
Te meter puts nothing inside that computer at risk. My bet is that
your problem lies within the power supply controller.
 
Intermittents are sometimes due to voltages that are completely
wrong. Two minutes with a 3.5 digit multimeter would tell more. There
is no "yes or no" voltage. There are numbers that should be reviewed
both before and when power switch is pressed. See the two minute
procedure in "When your computer dies without warning....." starting
6 Feb 2007 in the newsgroup alt.windows-xp at:
http://tinyurl.com/yvf9vh

Power supply controller is reset by removing power cord from AC
supply. If your problem is there, well, the meter may explain why -
especially from numbers for the purple wire and action of the green
and gray wire before and during powerup.
Click to expand...

I agree. I'd check the +5VSB rail (purple) and the PWR_OK pin (grey).
Both should measure +5V. I'd then press the front power switch and
verify that /PS_ON (green) drops from +5V to 0V and remains there. Use
any black wire as your ground.

See http://pinouts.ru/Power/atxpower_pinout.shtml

- Franc Zabkar
 
I agree. I'd check the +5VSB rail (purple) and the PWR_OK pin (grey).
Both should measure +5V.
Click to expand...

Actually, I'm not sure whether PWR_OK should be at +5V in standby
mode, but it should definitely measure +5V after the major rails have
powered up.
I'd then press the front power switch and
verify that /PS_ON (green) drops from +5V to 0V and remains there. Use
any black wire as your ground.

See http://pinouts.ru/Power/atxpower_pinout.shtml
Click to expand...


- Franc Zabkar
 
Actually, I'm not sure whether PWR_OK should be at +5V in standby
mode, but it should definitely measure +5V after the major rails have
powered up.
Click to expand...

Actual numbers when read with a multimeter: Green (Power On!) wire
must be more than 2 volts before power switch is pressed. Then must
drop below 0.8 volts when switch is pressed.

Once power supply decides power is stable, the Gray wire (Power OK)
voltage must rise from something near zero to above 2.4 volts.

Purple wire must be above 4.87 volts DC at all times - computer
powered on or off. Yes, specs provide a different number. But to
meet that other nunber, the digital multimeter must read 4.87 or
higher. These were defined in that two minute procedure at:
http://tinyurl.com/yvf9vh
 
w_tom <w_tom1 usa.net> wrote:

....
Nothing exposed in a computer that can harm you. Multimeter cannot
harm anything inside that computer.
Click to expand...

Anybody who knows anything about electronics knows that's bullshit.
Any time you stick conductive metal into a live circuit you risk doing
harm to the device and maybe to yourself.
John Doe is doing what he always does because he was exposed many
times posting technical myths.
Click to expand...
To appreciate his integrity, search on posts using the search terms
"John Doe" and "Mark Bender".
Click to expand...

Good idea. Search the Internet for Mark Bender and Tonal Voltmeter.
Then ask w_tom for proof of what he has done in electronics besides
spread potentially harmful advice in public forums.
 
Anybody who knows anything about electronics knows that's bullshit.
Any time you stick conductive metal into a live circuit you risk doing
harm to the device and maybe to yourself.
...
Good idea. Search the Internet for Mark Bender and Tonal Voltmeter.
Then ask w_tom for proof of what he has done in electronics besides
spread potentially harmful advice in public forums.
Click to expand...

John Doe does not post a single electrically useful fact. Other who
knows about electronics replied to John Doe's attacks by accurately
identifying him ignorant. His proof of superiority is personal
attacks? That is a responsible or useful reply? saltbeet - please be
careful. Appreciate the difference between a responsible solution -
with numbers - verses one based in hate and emotion. Fear of new
ideas and new techniques is widespread; identified by personal attacks
without any technical facts.

Franc Zabkar has identified a most likely suspect - where the prime
suspect may lie. A two minute procedure in "When your computer dies
without warning....." starting 6 Feb 2007 in the newsgroup
alt.windows-xp at:
http://tinyurl.com/yvf9vh
describes how to get those numbers - how to identify the suspect.

Notice how Valentin followed that procedure in http://tinyurl.com/yvf9vh.
Your input in this particular problem is greatly appreciated. I did
buy a digital multimeter (Radio Shack $20) and it's so easy to use.
Click to expand...

A complete contradiction of John Doe's claims. Valentin took those
numbers with a meter to identify a power supply controller as
defective - in minutes. Others then replied by attacking Valentin for
obtaining a useful answer. View yourself how many 'computer experts'
will post personal attacks only because a smarter solution was used.
Fear of working smarter with a simple meter is widespread:
http://tinyurl.com/3aslez

As Valentin notes, only w_tom provided a conclusive answer with
numbers from the meter:
1.What I was actually told [by others] is that besides motherboard
everything else was old and "obsolete". I dare you to find a single
persons quote stating that the motherboard was defective,
providing even a small _proof_ that this is the case. Since you're
the one who opened his mouth about "you were told", you should
have no trouble finding such a quote.

2. The offered suggestions, even by people who meant well, were
all in the area of 'try this and try that'.
Click to expand...

See the many (ie Rebecca, Damian) who attacked Valentin - as John
Doe posts - only because a meter gave a correct and useful answer in
minutes:
http://tinyurl.com/3aslez

Get the meter. Get conclusive answers. Ignore those who fear to
learn; whose assumptions are justification for attacking the
messenger. Those naysayers even attacked Valentin viciously in
http://tinyurl.com/yvf9vh because the meter exposed shotgunning as a
solution by the technically naive.
 
There is nothing new about troubleshooting with a multimeter. But most
technicians understand and are willing to advise about the dangers of
working on powered electronic devices, especially by people who have
no training. Using blackbox techniques to troubleshoot is a lot newer.
Sound like another of w_tom's deep-seated personal problems
manifesting itself by potentially harmful advice here on USENET.









<Snipped another w_tom idiotic rant>

See also:
surge suppressor
 
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