Epson 486SX - Manual (Page 163)

9. If you installed an EGA or VGA display adapter card, or
another type of card that you want to be the primary
display adapter, you must set jumper JP4 to disable the
built-in VGA adapter. Otherwise, you will not see any
display on the screen. See “Changing the Jumper Settings”
in Chapter 6 for instructions.
If you are using one or more display adapter cards, you
may also need to change the setting of jumper JP6. This
jumper tells the computer whether you are using a color or
monochrome monitor. (JP6 is set for color at the factory.)
When this jumper is set incorrectly, you see a CRT error
message.
If you are using two different video cards, set jumper JP10
to the primary monitor type. See “Changing the Jumper
Settings” in Chapter 6 for instructions.
10. If your computer suddenly stops operating, its power
supply thermal detection circuits may have detected
excessive operating temperatures and automatically shut
down the power. This protects your system from damage
due to overheating.
When these circuits detect a high temperature, they shut off
all the DC outputs in the power supply and cause it to go
into latch-offstate. This does not damage the power supply,
but you must correct the temperature problem before you
can use your computer again. See “Restoring the Power
Supply,” below.
B - 8 Troubleshooting