IBM PCjr Hardware Maintenance And Service page 182

1. Set the system unit's Power switch to Off.
2. Remove the modem and set it aside. Make a note
that this is modem #1.
3. Attach a new modem to the system board. Make a
note that this is modem #2.
4. Set the system unit's Power switch to On.
5. Bring the advanced-test menu to your display
IS THE ID UNDER THE MODEM SYMBOL
BLINKING?
Replace the system board.
Reattach the original modem (modem #1).
Repeat advanced POST and the advanced
tests to ensure that the IBM PCjr is operating
correctly.
The problem has been corrected. Repeat
advanced POST and the advanced tests to
ensure that the IBM PCjr is operating
correctly.
3-830-6 Internal Modem