2430 Super VGA Video Card – 5
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Hot insertion - Plugging cards into the card cage with the
power on will usually not cause a problem. (Octagon urges
that you do not do this!) However, the card may be damaged
if the right sequence of pins contacts as the card is pushed into
the socket. This usually damages bus driver chips and they may
become hot when the power is applied. This is one of the most
common failures of expansion cards.
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Using desktop PC power supplies - Occasionally, a customer
will use a regular desktop PC power supply when bringing up a
system. Most of these are rated at 5V at 20A or more.
Switching supplies usually require a 20% load to operate
properly. This means 4A or more. Since a typical Micro PC
system takes less than 2A, the supply does not regulate
properly. Customers have reported that the output can drift up
to 7V and/or with 7-8V voltage spikes. Unless a scope is
connected, you may not see these transients.
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Terminated backplanes - Some customers try to use Micro PC
cards in backplanes that have resistor/capacitor termination
networks. CMOS cards cannot be used with termination
networks. Generally, the cards will function erratically or the
bus drivers may fail due to excessive output currents.
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Excessive signal lead lengths - Another source of failure that
was identified years ago at Octagon was excessive lead lengths
on digital inputs. Long leads act as an antenna to pick up noise.
They can also act as unterminated transmission lines. When 5V
is switch onto a line, it creates a transient waveform. Octagon
has seen submicrosecond pulses of 8V or more. The solution is
to place a capacitor, for example 0.1 µF, across the switch
contact. This will also eliminate radio frequency and other high
frequency pickup.
