NEC PX-50XM4, Service Manual

Page: 266 / 535

5. The closed caption (CC) is displayed incorrectly. (PX-*****A only)
Waveform at Point B/D/E
Check point: Check voltage and see whether a change in H/L is present.
Waveform at Point C
CC is displayed incorrectly.
(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.
The MAIN PWB
is fault.
The CCD PWB is fault.
NO
Is there a digital waveform output
(3.3Vp-p) of H/L at Point D of Fig. 1?
NO
YES
NO
YES
The CCD PWB is fault.
The MAIN PWB is fault.
YES
YES
The MAIN PWB is fault.
NO
3.3Vp-p
NTSC video signal (with gray scale input)
1Vp-p
In the state that the CCD PWB is
dislodged, are there a voltage output
of 6.0Vdc at Pin 3 of the PV
connector and 3.3Vdc at Pin 1 of the
PN connector in the MAIN PWB?
NO
YES
The CCD PWB is fault.
Is there a digital waveform output
(3.3Vp-p) at Point E (in 4 places) of Fig.
1?
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?
Are there voltage outputs of
3.3Vdc and 6.0Vdc as specified
in Fig. 1 on next page?
CONFIDENTIAL
5-19