ViewSonic VS11770-1M, Service Manual

Page: 34 / 100

1.5. TV receiving test:
1.5.1 TV SIGNAL TEST ITEM
CENTRALISM TRANSMITTING SIGNAL CHECK CONTENT
SET CONTENT
CHANNEL
ORDER
FREQUENCY
(MHz)
PATTERN SOUND P/S(dB)
CHECK
CONTENT
CHANNEL 2
55.25 MONO SCOPE SWEEP TONE -10 ELECTRIC
ABNORMITY SOUND
CHANNEL 6
83.25 COLOR BAR 400Hz -10 SOUND ,PICTURE
CHANNEL 7
175.25 Full White (100
IRE)
STEREO -10 STERO FUNCTION
CHANNEL 13
211.25 STAIR DUAL -10 SUB FUNCTION
CHANNEL 14
471.25 MULTIBURST MONO -16 IMAGE AND SOUND
DISTURB
CHANNEL 36
603.25 MULTIBURST MONO -10 TEST Close-caption T1
FUNCTION
CHANNEL 69
801.25 MONO SCOPE MONO(1KHz) -10 NOISE LIMMITTED
SENSITIVITY
TV TEST METHOD
A.CHANNEL2 Examines sound by ear, whether the sound does have mechanical resonation and
the electrical unusual sound, and image to sound disturbance.
B.CHANNEL6: Check sound and picture.
C.CHANNEL7: Examines whether the sound does receive the image disturbance, Judgment basis:
Whether there is unusual sound, input signal LEVEL<=36dBu,and STEREO SENSITIVITY is
normal.
D.CHANNEL13: Under main/sub/main-sub mode, check sub function.
E.CHANNEL14: Examines whether the sound does receive the image disturbance, Judgment basis:
Whether there is unusual sound.
F. CHANNEL 36:Check T1 of close-caption. Input signal level<=45dBu.
G.CHANNEL 69: Adjustment attenuator, If the critical point of the change of the image signal to
noise ratio is under LEVEL<=60dBu, regards as normally.
PRODUCTS OUTPUT CHECK ITEM.
A. The same as " CENTRALISM TRANSMITTING SIGNAL CHECK CONTENT"
B. saturation TEST, inputs the TV signal, the input signal LEVEL establishment most greatly is
90dBu,check whether CONTRAST of the image is normal; Whether appears the disturbance
phenomenon.
C.AFT CHECK,
(1) The frequency of the input TV signal is 211.25MHz (CH13), after confirmed the TV set
receives this signal, closure radio station; Then set frequency of the TV signal generator to be
212.25MHz, turn on the TV set and check whether the TV set receives the signal of CH13.
(2). The frequency of the input TV signal is 211.25MHz (CH13), after confirmed the TV set
receives this signal, closure radio station; Then set frequency of the TV signal generator to be
212.00MHz, turn on the TV set and check whether the TV set receives the signal of CH13.
(3). After all of FUNCTION TEST completed, we must erase all saved changes again and
restore the factory defaults.
1.6. DTV TEST ITEM
CHANNEL
FREQUENCY SOUND dB PETTEN CHECK CONTENT
14
471.25MHz Y 50 Dynamic picture Picture
36
603.25MHz Y 50 Color bar Color
69
801.25MHz Y 75 Dynamic picture Sound and Picture
DTV CHECK METHOD
A
.
CHANNEL14: Check whether there are some pause or the mosaic phenomenon in the picture.
B.CHANNEL36: Check whether the color of the color bar is normal.
C.CHANNEL69: Turn RF attenuator and check the critical point of the change of the image’s
S/N is under LEVEL<45~85> dBu, regards as normally.
ViewSonic Corporation
Confidential - Do Not Copy
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3235
w-1M
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