IBM 3274 User Manual page 88

Service/Replacement Procedure on page 2-6. (If you have
just replaced your 3299, and a
D
symbol is still not
displayed, then request service for your 3274.)
6. If a
D
symbol is still not displayed, you now need to
determine whether the signal cable is bad or the 3274 port
defective.
7. At the suspected 3274 device panel, connect a known
working display and a known working signal cable. At the
display station, set the Normal/Test switch to Test, then
back to Normal, or turn power off, then on, and wait up to
2 minutes, whichever is appropriate.
8. If a
D
symbol is now displayed, you have determined that
the signal cable is defective. Contact the person
responsible for cable repair or replacement. If a
D
symbol is not displayed, the 3274 port is probably defective.
Recheck customization, and request appropriate service.
9. Restore all devices and signal cables to their original
configuration. At the 3274 device panel, move the switch
to the down position, or disconnect the shorting cap,
whichever is appropriate. (See Figure 2-1
D
on page
2-51.)
10. If, after following the .above procedures, you still have all
3299 attached devices failing, request appropriate service.
Section 2. Problem Determination
2-13