IBM 6648 Personal Computer User Manual


 
Undetermined problems
Check the power supply voltages. See Power supply on page 108. If the
voltages are correct, return here and continue with the following steps.
1. Power-off the computer.
2. Remove or disconnect the following components (if installed) one at a
time.
a. Non-IBM devices
b. External devices (modem, printer, or mouse)
c. Any adapters
d. Memory modules
Before removing or replacing memory modules, see System board
memory on page 135.
e. Extended video memory
f. External Cache
g. External Cache RAM
h. Hard disk drive
i. Diskette drive
3. Power-on the computer to re-test the system.
4. Repeat steps 1 through 3 until you find the failing device or adapter.
If all devices and adapters have been removed, and the problem continues,
replace the system board. See Replacing a system board on page 125.
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