I've noticed a disturbing trend with computers cases not being properly grounded.
This appears to especially be a problem with the cheaper cases.
It is critically important that the metal panels of the case to all be connected
to the earth ground. This is provided on a properly built case via the ground
pin of the power supply cord. Improper grounding can cause anything from
intermitent failure to outright catastrophic destruction due to static discharge.
An unground case can also cause interference with cell phones, Bluetooth, Wifi
and other equipment that use RF signals to communicate as the lack of a proper
ground significantly reduces the ability of the case to divert the RF signals
generated by the electronics to the earth ground.
The problem occurs especially in the cheaper cases where the various panels
in the case are all separately painted then riveted together. The paint prevents
the panels from being electrically attached to each other.
With out a proper ground a static discharge has no place to go except through
your expensive electronics inside that improperly designed case. If you're
lucky it will only cause a glitch or a crash. If you are unlucky it will
destroy your electronics.
A quick way to check if the case is properly designed is first do a visual.
Do you see paint under the area where the panels meet? That is a potential
indicatin of a problem. A better check is to use a VOM to test the conductivity
of the case. The most critical is between the power supply ground and the
motherboard mount screws. With the power supply mounted in the case, but not
the motherboard, measure the resistance between the power supply ground and
the motherboard mounting jack screws. The resistence should be under one ohm
(preferably less than 0.2 ohms).
Note: You should do this without the motherboard in the case as it can
interfer with the measurement via the power and signal cabling. You also want
to make sure each jack screw is properly grounded.
Less important, but still an important issue is making sure the vaious panels
are properly grounded. This make required scratching some of the paint off
to gain access to the metal underneath. Each panel should show one ohm or
less resistance to the power supply earth ground.
A new case "enhancement" these days is screwless drive mounts. That makes it
easy to replace the drives, but it also prevents proper earth grounding of
the drives. Most are well enough designed these days that you can get away
without a proper earth ground, but it can potentially cause to problems.
Note: Cases that are not properly grounded will not pass UL, FCC, IEC, ISO
or any other electronics regulatory agency tests.
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