HardwareBanter - View Single Post - PSU died. Has it killed my motherboard too?

Paul · February 25th 06, 11:30 PM posted to alt.comp.hardware.pc-homebuilt

In article ,
lid (Wandy) wrote:

Hi, newbie here...I dont know a lot about P.Cs and really need help.

My 8 week old P.C, custom built from a (supposedly) reputable Ebay
store has died on me and I am distraught.

The PSU has died on the machine. I know this because I have made
'progress' by fitting a new PSU. When the original PSU failed the
machine would not power up at all, but would momentarily stutter in
to life as I pressed the case power switch but would then die as I
let go of the switch.

By fitting a new PSU I can get the machine to power on. The processor
fan starts to run but nothing else happens. There is no 'beep' sound
that is normally heard as the machine boots up. The large LED light
on the front of the case that used to illuminate green when the
machine was switched on now illuminates red.

My friend says that the PSU has probably blown my motherboard and told
me to check the capacitors to see if they look swollen. I have done
this but they look ok.

My machine spec is as follows:- Pentium 4 3GHz, 2GB RAM, ASRock 775
VM800 motherboard, 80Gb HD, 450W 'Win Power'??? PSU, X-Blade case.

To be honest I have had my doubts about the machine since I got it
because when I think about it now there has always been a strange
smell eminating from it. Also whenever I was using the machine and
running programs the tone of the fan running inside the machine used
to dip up and down. Is this normal?

The machine is under warranty but I am livid about the prospect of
sending it back after only 8 weeks, espacially when I have to cover
the courier costs. If I send it back I am concerned they will simply
replace the damaged PSU with one of exactly the same type, because my
hunch is that the PSU is a poor quality one.

So what do you think? Has the PSU ruined my machine or is there
something that I have missed?

Your help would be very much appreciated!!!!

A new motherboard of the same type, would be about $50.
How much would the shipping costs be, to get warranty service ?

What you could do, is send it back, have them repair it. When it
returns, immediately pull the cheap PSU and put something better in
its place.

Fan speeds on equipment can go "up and down", if the voltage
fed to the fan is temperature controlled, or if the voltage
being used is not regulated very well. The human ear is pretty
sensitive to pitch, and in fact it doesn't take a lot of
voltage change, for the fan pitch to change enough for your
ear to detect it. The computer I'm typing this on, one of
the cooling fan slows down when the CPU is at 100%, and in
fact that is an easy way for me to tell if some task has the
machine running flat out.

ATX power supplies are not tightly regulated, because on at
least some of them, there is only one control loop controlling
all the outputs simultaneously. Some of the voltage relationships
are established by the turns ratio of the output transformer.
Other power supplies have independent regulation. So, in fact,
not all ATX power supplies are designed the same way. It is
fair to say, that the cheapest supplies use one control loop.
And it is not possible to tell how it is designed, by reading
the advert for the PSU.

Smelly PSU ? The last three I bought smelled, and they were not
the cheapest ones you could buy. One smelled like an organic
solvent was still in the box. The odor in the others, lingers
for years afterwards. Smelly product seems to be a side effect
of offshore manufacturing. And the funny thing is, the majority
of users seem to be oblivious to these smells.

Paul