Octagon Systems X-COM-2 Reference Manual page 3

Please read the following section before installing your product:
Octagon's products are designed to be high in performance while consuming
very little power. In order to maintain this advantage, CMOS circuitry is
used.
CMOS chips have specific needs and some special requirements that the user
must be aware of. Read the following to help avoid damage to your card from
the use of CMOS chips.
Using CMOS circuitry in industrial control
Industrial computers originally used LSTTL circuits. Because many PC
components are used in laptop computers, IC manufacturers are exclusively
using CMOS technology. Both TTL and CMOS have failure mechanisms, but
they are different. Described below are some of the failures that are common
to all manufacturers of CMOS equipment.
The most common failures on CPU control cards are over voltage of the power
supply, static discharge, and damage to the serial and parallel ports. On
expansion cards, the most common failures are static discharge, over voltage
of inputs, over current of outputs, and misuse of the CMOS circuitry with
regards to power supply sequencing. In the case of the video cards, the most
common failure is to miswire the card to the flat panel display. Miswiring can
damage both the card and an expensive display.
Testing "dead" cards: For a card that is "completely nonfunctional",
there is a simple test to determine accidental over voltage, reverse
voltage or other "forced" current situations. Unplug the card from the bus
and remove all cables. Using an ordinary digital ohmmeter on the 2,000
ohm scale, measure the resistance between power and ground. Record
this number. Reverse the ohmmeter leads and measure the resistance
again. If the ratio of the resistances is 2:1 or greater, fault conditions
most likely have occurred. A common cause is miswiring the power
supply.
Improper power causes catastrophic failure: If a card has had
reverse polarity or high voltage applied, replacing a failed component is
not an adequate fix. Other components probably have been partially
damaged or a failure mechanism has been induced. Therefore, a failure
will probably occur in the future. For such cards, Octagon highly
recommends that these cards be replaced.
Other over–voltage symptoms: In over–voltage situations, the
programmable logic devices, EPROMs and CPU chips, usually fail in this
order. The failed device may be hot to the touch. It is usually the case
that only one IC will be overheated at a time.
Power sequencing: The major failure of I/O chips is caused by the
external application of input voltage while the Micro PC power is off. If
IMPORTANT!
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