Hardware Reference
In-Depth Information
Power Supply Troubleshooting
Troubleshooting the power supply basically means isolating the supply as the cause of
problems within a system and, if necessary, replacing it.
Caution
It is rarely recommended that an inexperienced user open a power supply to make repairs
because of the dangerous high voltages present. Even when unplugged, power supplies can
retaindangerousvoltageandmustbedischarged(likeamonitor)beforeservice.Suchintern-
al repairs are beyond the scope of this topic and are specifically not recommended unless the
technician knows what she is doing.
Many symptoms lead me to suspect that the power supply in a system is failing. This can
sometimes be difficult for an inexperienced technician to see because at times little con-
nection seems to exist between the symptom and the cause: the power supply.
For example, in many cases a parity check error message can indicate a problem with
the power supply. This might seem strange because the parity check message specifically
refers to memory that has failed. The connection is that the power supply powers the
memory, and memory with inadequate power fails.
Ittakessomeexperiencetoknowwhenthistypeoffailureispowerrelatedandnotcaused
by the memory. One clue is the repeatability of the problem. If the parity check message
(or other problem) appears frequently and identifies the same memory location each time,
I would suspect that defective memory is the problem. However, if the problem seems
random, orifthe memory location the errormessage cites ashaving failed seems random,
I would suspect improper power as the culprit. The following is a list of PC problems that
often are related to the power supply:
• Any power-on or system startup failures or lockups
• Spontaneous rebooting or intermittent lockups during normal operation
• Intermittent parity check or other memory-type errors
• Hard disk and fan simultaneously failing to spin (no +12V)
• Overheating due to fan failure
• Small brownouts that cause the system to reset
• Electric shocks felt on the system case or connectors
• Slight static discharges that disrupt system operation
• Erratic recognition of bus-powered USB peripherals
