NEC PX-50XM4 series Service Manual page 266

5. The closed caption (CC) is displayed incorrectly. (PX-*****A only)
(Caution) Only the models for North America. The PCB-5044 (CCD PWB) is not installed in other
models. Checks are needed by applying a signal output to the video input circuit, which is
equivalent to the closed caption.
CC is displayed incorrectly.
Are there voltage outputs of
3.3Vdc and 6.0Vdc as specified
in Fig. 1 on next page?
YES
Is there a CLK waveform output
(3.3Vp-p) of 27MHz at Point A of Fig. 1,
and also a digital waveform output
(3.3Vp-p) of H/L at Point B (in 3
places)? In addition, is there an analog
video signal waveform output (1Vp-p)
at Point C?
YES
Is there a digital waveform output
(3.3Vp-p) of H/L at Point D of Fig. 1?
YES
Is there a digital waveform output
(3.3Vp-p) at Point E (in 4 places) of Fig.
1?
YES
The MAIN PWB is fault.
Waveform at Point B/D/E
Check point: Check voltage and see whether a change in H/L is present.
Waveform at Point C
NTSC video signal (with gray scale input)
In the state that the CCD PWB is
dislodged, are there a voltage output
of 6.0Vdc at Pin 3 of the PV
NO
connector and 3.3Vdc at Pin 1 of the
PN connector in the MAIN PWB?
The CCD PWB is fault.
NO
The MAIN PWB is fault.
NO
The CCD PWB is fault.
NO
The CCD PWB is fault.
3.3Vp-p
1Vp-p
5-19
CONFIDENTIAL
NO
The MAIN PWB
YES
is fault.