Sharp VC-780E - Page 39

VC-780E
VC-790ET
Probable causes and countermeasures
* Check if there is chroma signal at pin 30 of !C501.
* APC is misadjusted (R506). It is not allowed 10
readjust them, this means that !C501 is detective.
* Check if 1C501 is normally functioning.
[
No colour appears. (PAL / MESECAM)
Make sure “NTSC 3.58 H” signal at pin 11 of K502
is at “H” level.
* Put the unit in playback mode and check if the
chroma signal is given out at pin 30 of IC5701.
* Check if APC (R5812) has been properly adjusted.
(If no adjustment is effective, the IC itself is
defective.)
* Check if the “ROTATION” pulse is put in to pin 5
of 1€5701. (If the output from the system
controller does not reach this ie the 1C5701 or
1€501 is defective.)
*
Put
the
unit
in
record
mode
and
see
if
the
chroma
signal
is
given
out
at
pin
16
of
1C5701.
* Be sure that the voltage at each pin of 1C5701 is as
specified.
No colour appears in NTSC 3.58
*
Make
sure
“SECAM
5V”
signal
at
pin
22
of
K503
is
at
"H"
level.
* Check if the chroma signal is applied at TP5702.
* Check if the gate (R5814 and R5815) has been
properly adjusted.
*
Check
also
if
the
bell
filter
(T5701,
T5702
and
T5703)
has
been
properly
adjusted.
* Be sure that the voltage at each pin of 1C5702 is as
specified.
No colour appears in SECAM mode.
* Put the unit in playback mode in NTSC mode and
make sure pins 6 and 10 of K401 are at 9V level.
Readjust the flicker control (R440).
With the unit in playback mode in NTSC mode,
check if the video signal is given out to the
emitter of Q4405.
* Then make sure the video signal is given out to
pin 12 of 1C4401.
* Finally make sure the 17-MHz clock waveform
signal is put in to pin 9 of 1C4401.
No picture appears over the screen in
still/slow mode or no lateral stripes
in SP search mode in NTSC 3.58/4.43
mode.
—
Excessive skew is found in SP search
mode in NTSC 3.58/4.43 mode.
*
Make
sure
the
pulse
signal
is
put
in
to
pin
3
of
K401.
The image above and
below the noise bars is
seen skew as sketched
here.
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