NEC PX-50XM4 series Service Manual page 265

(2) The wireless remote control is not effective.
(Caution) Since the detection of "wired" or "wireless" is conducted for the remote control
through the remote terminal, it is necessary to pull out the remote control cable
from the remote terminal, without fail. Troubleshooting should be carried out after
confirming that "IR REMOTE" is set at ON and that "ID NUMBER" is at ALL
according to the user's menu.
The wireless remote control is not
effective.
Is there a 0Vdc output at Pin 12 of the
RS connector?
YES
Is there a signal output specified
below at Pin 6 of the PW connector?
NO
Is there a signal output specified
below at Pin 1 of the LD connector?
NO
The LED connector or the LED PWB is fault.
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When the RS connector is disconnected,
NO
is there a 0Vdc output at Pin 12 of the RS
connector in the MAIN PWB?
NO
5Vp-p
YES
The MAIN PWB is fault.
YES
The PW connector or the
PWR PWB is fault.
5Vp-p
5-18
YES
The 232C PWB or the RS
connector is fault.
CONFIDENTIAL