UPGRADING REPAIRING PCs

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Table 2.15 Troubleshooting Power Supplies Continued
Symptom Cause(s) Tests and Solution(s)
System reboots Incorrect power level on Use DC-voltage digital multimeter
itself. Power_Good; can indicate (DMM) to test P8-1 (orange wire)
overloaded power supply on LPX and older power supplies
or otherwise bad unit or Pin 8 (gray wire) on ATX and
newer power supplies; rated voltage
is +5v; acceptable is +3.0v to
+6.0v.
Replace failed power supply with
higher rated unit.
Fan turns for Wrong voltage (PS set to Turn off system; reset PS to
only a moment 220/230v in U.S.) correct voltage (110/115v in
and then stops. U.S.) and restart. Using 220/230v
power on a PS set for 110/115v
will destroy it!
Dead short in system Short can be caused by loose
screws, failed hard drives, or addon
cards.
Turn off and unplug system; disconnect
hard drive and see
whether system starts. If system
still fails, plug in drive and remove
add-on card; repeat until each
card and drive has been checked;
also check Y-adapter cables
because bad cables can cause
shorts.
Note
Chapter 2—System Components and Configuration
Replace faulty component(s).
For more information on power supplies, wattage ratings, and
testing, see Chapter 21 of Upgrading and Repairing PCs, 12th
Edition, published by Que.
Memory Types
RAM (random access memory) provides the work area that processors
use to create and modify data. While RAM was sometimes
found on expansion boards on old XT-class and early AT-class systems,
all standard 486-based and Pentium-class systems have their
memory modules attached to the motherboard.
Memory modules come in two major forms: SIMMs and DIMMs.
SIMM stands for single-sided inline memory module, and DIMM
stands for dual-sided inline memory module. These terms refer to
the pin configurations used on the module, rather than the location
of the memory chips on the module.