Power problems

[James Halen]

I got a new case a few weeks ago. Black, sidepanel window, 400 watt
power supply. My problem is this, at random occasions, it shuts down
for no reason.
Also, every now and then, if I touch the case, like when inserting a
cd rom, it immediately turns off. Sometimes I can touch the case and
it doesn't happen, other times, I barely tap it and zap, off it goes.

In my old case, this didn't happen, the parts are the same and I don't
know what's going on. My only guess is that the power supply is bad or
its not grounded, but I know my motherboard, cpu, video card, etc.
work fine.

[Charles Howse]

Previously James Halen <Deatharcher@hotmail.com> wrote: I got a new case a few weeks ago. Black, sidepanel window, 400 watt power supply. My problem is this, at random occasions, it shuts down for no reason. Also, every now and then, if I touch the case, like when inserting a cd rom, it immediately turns off. Sometimes I can touch the case and it doesn't happen, other times, I barely tap it and zap, off it goes.
In my old case, this didn't happen, the parts are the same and I don't know what's going on. My only guess is that the power supply is bad or its not grounded, but I know my motherboard, cpu, video card, etc. work fine.

Yes, likely impoper gounding. What it does in your case is
(careful, I am speculating) is building up some voltage on the case.
Then when you tap it or the charge arcs away, it flows close
by the power switch line or the power-on line from the mainboard
in some place and induces a signal there. This then tells the PSU
to switch off.

There is at least two problems here:
1. The improper grounding
2a.Improper filtering on the power-switch/power-on lines in the PSU.
These lines should onlu react to a longer, solid signal change
(e.g. > 10ms), which a short arcing/charge drain should not produce.
In addition they should require a significant driving force
(e.g. 1TTL load) to activate, again which charge drain like this
should not be sufficient to induce.
2b.Alternatively the power-swicth/power-on lines are fine
and some part of the mainboard power circuitry panics when
you tap the case. This still requires improper grounding.

Speculating futher, I would say the PSU is badly designed or broken.

One thing you can do to verify is measure the resistance between
the case and ground. It should be << 1 Ohm.

Another thing you can try is taping the case with a good isolator
(plastic, glass) and see whether you can get it to swicth of that
way. Very seldomly you get contact errors that are extremely sensitive
to mechanical shock.

Solution: If improper grounding is involved (see the two tests I propose)
you should get rid of the PSU. If it develops other problems (and if
it has one design/manufacturing problem it may have more) it could
cause a fire or kill people. Destroy it, do not sell it, do not give
it away.

Arno
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