Epson 10020 - Manual (Page 116)

Changing the Jumper Setting
To disable the built-in diskette drive controller, you need to
change the setting of Jumper J1 on the main system board. See
the illustration above for the location of this jumper, near the
option slots. If an option card is installed in slot number five,
you may need to remove the card to reach the jumper.
A jumper is a small electrical connector that controls one of
the computer’s functions. A jumper’s setting is determined by
where the jumper is placed: either between pin A and the
middle pin (position A) or between pin B and the middle pin
(position B), as shown below.
The factory setting for Jumper J1 is position A. To disable the
internal diskette drive controller, move the jumper to position
B. Use needle-nose pliers or tweezers to lift it off the board and
gently move it to the other position. Be careful not to lose it or
leave it out of the computer.
If you have also installed an additional disk drive, remember to
adjust the appropriate DIP switches on the front panel to
match the number of drives installed.
4-12 Installing Option Cards