PSU or MOBO failure?
Geoff
I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII
processors), which is now only used for backup, but is quite useful in
that role.
It is refusing to boot. No POST, no beeps. The only signs of life are :
(1) the mobo led is lit (2) there is power to the NIC (3) sometimes I get
a tiny flicker of life on the case power-on led (4) a cpu fan may give one
or two revolutions then stop.
Does this sound like PSU failure ? A replacement would be cheap enough to
risk, but there is obviously no point in bothering at all if someone knows
that this is far more likely to be the mobo.
Thanks,
Geoff
Måns Rullgård
It could be the PSU. To see if this is the case, measure the voltage
on a hard disk power plug while attempting to power on the machine.
If you do not get the proper 5V and 12V readings, chances are the PSU
is broken. To completely rule out the MB, unplug all PSU connections,
and short pins 13 and 14 (black and green) on the main ATX plug from
the PSU. This should activate the PSU, and you should be able to
measure the various voltages.
--
Måns Rullgård
ma...@mansr.com
Hactar
What's gotten me a few times is the big 20- or 24-pin connector PS ->
mobo sometimes looks seated but isn't. No POST but fans are the normal
symptoms, but I suppose it could be otherwise depending on what's
contacted. Make sure you hear a click.
If you buy a replacement PS, do it from a place with a good return
policy in case that isn't the cause. Newegg is pretty good.
--
-eben QebWe...@vTerYizUonI.nOetP http://royalty.mine.nu:81
CANCER: The position of Jupiter says that you should spend the
rest of the week face down in the mud. Try not to shove a roll of
duct tape up your nose when taking your driver's test. -- Weird Al
Douglas Mayne
I am not sure if any Asus boards had bad capacitors, or not, but many
motherboards from that generation suffer from bad capacitors. Do you
notice any bulging or leaking capacitors, especially around the main power
tap? If it's bad caps, then that may be it for that board unless you can
find someone who can do the technical soldering that is required.
--
Douglas Mayne
Geoff
<snip>
> It could be the PSU. To see if this is the case, measure the voltage on
> a hard disk power plug while attempting to power on the machine. If you
> do not get the proper 5V and 12V readings, chances are the PSU is
> broken. To completely rule out the MB, unplug all PSU connections, and
> short pins 13 and 14 (black and green) on the main ATX plug from the
> PSU. This should activate the PSU, and you should be able to measure
> the various voltages.
Thank you very much Måns,
I dug out my ageing multimeter and did the HDD power plug test. The
result is as follows. If I (1) switch off the mains input, (2) switch the
mains back on (3) power on the machine .. then I get a flicker of power on
both the 5v an 12v pins ... it is momentary and coincides with one or two
revolutions of a cpu fan. The machine is then completely dead until I
cycle the mains input on and off again - powering on the machine without
cycling the mains in this way has no effect.
I have not yet shorted pins 13 and 14 .. I am rather at the limit of what
I understand here and (while I am sure you are giving me good advice), I
am a little nervous about doing that. I may pluck up courage later.
Geoff
Geoff
<snip>
> What's gotten me a few times is the big 20- or 24-pin connector PS ->
> mobo sometimes looks seated but isn't. No POST but fans are the normal
> symptoms, but I suppose it could be otherwise depending on what's
> contacted. Make sure you hear a click.
>
> If you buy a replacement PS, do it from a place with a good return
> policy in case that isn't the cause. Newegg is pretty good.
Thanks Hactar,
You will see that I have responded directly to Måns. I have checked that
the connector is well seated, and it seems to be ok. I am in the UK and
will pick up a cheap PSU at one of my local stores if that seems to be the
way ahead. I am lucky in living near to a couple of big distributors. I
don't know if they will allow me a refund, but I don't mean to spend a lot
on this box and will just have to take the risk if the PSU does not turn
out to be the problem.
Geoff
Geoff
<snip>
> I am not sure if any Asus boards had bad capacitors, or not, but many
> motherboards from that generation suffer from bad capacitors. Do you
> notice any bulging or leaking capacitors, especially around the main
> power tap? If it's bad caps, then that may be it for that board unless
> you can find someone who can do the technical soldering that is
> required.
Thanks Douglas,
You will see that I have responded directly to Måns above. I have had a
good look at the mobo and can't see any obvious problems. I am guessing
that result I am seeing may be something to do with capacitance somewhere
(as if I am getting a small build up of charge when the mains is cycled),
but I am just surmising and I don't know if it is more likely to be in the
PSU or on the MOBO.
Geoff
Hactar
Geoff <capst...@yahoo.co.uk> wrote:
>
> You will see that I have responded directly to Måns. I have checked that
> the connector is well seated, and it seems to be ok. I am in the UK and
> will pick up a cheap PSU at one of my local stores if that seems to be the
> way ahead. I am lucky in living near to a couple of big distributors. I
> don't know if they will allow me a refund, but I don't mean to spend a lot
> on this box and will just have to take the risk if the PSU does not turn
> out to be the problem.
Also, my motherboard or PS (one of them) would show the same symptoms if
there was a short somewhere. Checked that? Bad/loose RAM, card, CPU?
--
-eben QebWe...@vTerYizUonI.nOetP
1101000 1110100 1110100 1110000 0111010 0101111 0101111 1110010 1101111
1111001 1100001 1101100 1110100 1111001 0101110 1101101 1101001 1101110
1100101 0101110 1101110 1110101 0111010 0111000 0110001 0101111
Geoff
<snip>
> I have not yet shorted pins 13 and 14 .. I am rather at the limit of
> what I understand here and (while I am sure you are giving me good
> advice), I am a little nervous about doing that. I may pluck up courage
> later.
>
Following up my own post, I shorted the pins. I am seeing a consistent ~
1.5v on both the 5v and 12v pins. On that basis I will change the PSU
unless someone tells me I am wrong.
Thanks again,
Geoff
Geoff
> Also, my motherboard or PS (one of them) would show the same symptoms if
> there was a short somewhere. Checked that? Bad/loose RAM, card, CPU?
Thanks Hactar,
As you will see, I followed up my own post to say that I am getting only ~
1.5v having shorted the pins. I will try a new PSU I think.
Geoff
david
say:
Most power supplies need some minimum load on them to operate. Make sure
you have something on it (like an old disk drive) that can provide a load
when you do the test.
Geoff
< snip >
>
> Most power supplies need some minimum load on them to operate. Make
> sure you have something on it (like an old disk drive) that can provide
> a load when you do the test.
Thank-you David,
Since the PSU is still in the machine, I repeated the test with the
existing HDD as load (with and without the ribbon cable attached). I
repeated with an old HDD too. Same result as before.
Geoff