I think I have a bad PC power supply. It turns on and runs but the
attached motherboard will not operate.

After testing some other known-to-work power supplies, I think that
the power good line on the supply in question is not working. Other
working supplies put out +5VDC on this line while this supply puts out
nearly nothing.

I just need to confirm that +5VDC is what should appear on the power
good line. Googling around hasn't provided any good info on this.

Thanks in advance!

William

wrote:

I think I have a bad PC power supply. It turns on and runs but the
attached motherboard will not operate.

After testing some other known-to-work power supplies, I think that
the power good line on the supply in question is not working. Other
working supplies put out +5VDC on this line while this supply puts out
nearly nothing.

I just need to confirm that +5VDC is what should appear on the power
good line. Googling around hasn't provided any good info on this.

Yes. +5v. But only after all monitored voltages are within specification.

Are they?

Hi!

Yes. +5v. But only after all monitored voltages are within specification.
Are they?

Yes. All the other voltages are right where they should be and are stable
even when approaching the maximum rating of the PSU. I've never seen
anything like it before.

The power good line isn't completely dead--it has a fraction of a volt on it
all the time.

William

In article
,
wrote:
I just need to confirm that +5VDC is what should appear on the power
good line. Googling around hasn't provided any good info on this.


http://www.helpwithpcs.com/courses/p...nc-pinouts.htm

--
*Reality is a crutch for people who can't handle drugs.

Dave Plowman London SW
To e-mail, change noise into sound.

William R. Walsh wrote:
Hi!

Yes. +5v. But only after all monitored voltages are within specification.
Are they?

Yes. All the other voltages are right where they should be and are stable
even when approaching the maximum rating of the PSU. I've never seen
anything like it before.

The power good line isn't completely dead--it has a fraction of a volt on it
all the time.

William




My guess is that the fault is in the power good circuit, I've never
really looked into how this works but I suspect it isn't very complicated.

wrote:

I think I have a bad PC power supply. It turns on and runs but the
attached motherboard will not operate.

After testing some other known-to-work power supplies, I think that
the power good line on the supply in question is not working. Other
working supplies put out +5VDC on this line while this supply puts out
nearly nothing.

I just need to confirm that +5VDC is what should appear on the power
good line. Googling around hasn't provided any good info on this.

Thanks in advance!

William
Short of a defective PG detection circuit, it's very possible you could
have some weak caps that are not totally filtering correctly and the
circuit see's a little switching noise.

--
http://webpages.charter.net/jamie_5"

James Sweet wrote:

My guess is that the fault is in the power good circuit, I've never
really looked into how this works but I suspect it isn't very complicated.


http://images.google.com/images?um=1&hl=en&rls=com.microsoft%3Aen-us%3AIE-SearchBox&rlz=1I7GGLD&q=atx+power+supply+schematic


--
http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm

On May 6, 12:57*pm, wrote:
I think I have a bad PCpower supply. It turns on and runs but the
attached motherboard will not operate.

After testing some other known-to-work power supplies, I think that
the power good line on the supply in question is not working. Other
working supplies put out +5VDC on this line while this supply puts out
nearly nothing.

I just need to confirm that +5VDC is what should appear on the power
good line. Googling around hasn't provided any good info on this.

Voltage on Power Good must exceed 2.4 volts. Significant also is that
number to three digits. If this does not occur, typically voltages on
any orange, red, or yellow wire is defective. Green wire orders power
supply on. Supply has about 2 seconds to measure orange, red, and
yellow voltages. If OK, gray (Power Good) wire goes to less than 0.8
to well above 2.4 volts

Now, if power supply controller does not see power good, then power
supply controller will turn off power supply. So, first see what one
of orange, red, yellow, and purple wires do both before and when power
switch is pressed. Purple should remain above 4.87 at all times (and
also related to number on Power Good wire). Other voltages should
rise from zero until power supply controller cuts them off. Any one
voltage that does not increase as the power switch is pressed implies
where to look for the problem.

Other possibility is that a failure exists in the power supply
controller or Power Good driver is defective. With power supply
disconnected from motherboard, connect the meter in DC volts, shunt a
paper clip from green wire to black wire, then record that voltage.
Repeat same experiment with meter in Ampere mode between that Gray
(Power Good) wire and any black (ground wire). When a paper clip
connects green wire to black wire, then current on Power Good should
significantly exceed 0.02 amperes (20 mA). Set meter to highest
current. Short the green wire (Power On#) to ground, then slowly
decrease meter scale until a useful current number is read.

That Power Good wire must output more than 2.4 volts and 0.02
amperes. Those numbers will report things significant. And then post
those numbers here to learn other facts. Those numbers may be
reporting more than you realize.

Hi!

http://www.helpwithpcs.com/courses/p...nc-pinouts.htm

Thanks for the link. I already saw it though, and unless there is
something I missed, it does not give a voltage for the Power Good pin.
The only identification I saw there was "PWR_OK" with no further
explanation offered.

William

Hi!

Short of a defective PG detection circuit, it's very possible you
could have some weak caps that are not totally filtering correctly
and the circuit see's a little switching noise.

It would surprise me (only a little, so you know my expecations have
been lowered) to find something brand new coming out of the box with
bad caps.

I don't know what might have caused it. The supply seemed to have
excellent regulation on all other outputs. All of the 3.3, 5 and 12
volt leads tested fine. In any case, I traded it off for a new supply
under warranty and that one happens to work.

William

wrote in message
...
Hi!

http://www.helpwithpcs.com/courses/p...nc-pinouts.htm

Thanks for the link. I already saw it though, and unless there is
something I missed, it does not give a voltage for the Power Good pin.
The only identification I saw there was "PWR_OK" with no further
explanation offered.

William


Take a look at the page at http://www.pavouk.org/hw/en_atxps.html. It gives you
a sample ATX power supply schematic, plus a decent description of the operation,
including the "Power_Good" circuit.

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

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.