CCE HPS-2007, Руководство по обслуживанию

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HPS-2007
20
2.6 Video
2.6.1 Sensibility and Signal /Noise Rate
a) Adjust the TV to a “PP” condition.
b) Apply to the antenna input a 60dB
µ
V signal with 60% AM modulation, 1kHz sine wave
(Frequency and channel factory defined).
c) Connect at the output video detector na AC voltmeter and read the voltage V
AC.
d) Turn off the AM modulation and read the noise level “Vr” (AC voltmeter)
.
e) Calculate the signal-noise rate as following:
S/N=20 log (V
AC
/ V
R
).
f) Reduce the output level signal generator till the rate S/N reach 20 dB. In this condition the
output level signal generator is the sensibility in dBuV.
Minimum Nominal Maximum Unit
Sensibility - 37,00 46,00
dB
µ
V
S/N 40,00 50,00 - dB
2.6.2 AGC circuit :
a) Apply to the antenna input a 60dB
µ
V signal with 88% AM modulation with “WHITE” pattern
(Frequency and channel factory defined), and FM sine wave 400 Hz audio modu-25
kHz deviation.
b) Adjust the TV to “PP” condition
c) Read the DC voltage at the tuner AGC terminal. Utilize a DC electronic voltmeter with
minimum 10 M
Ω
impedance.
Minimum Nominal Maximum Unit
3,00 4,00 5,00 V
DC
2.6.3 AFT circuit.
a) Apply to the antenna input a 60dB
µ
V signal with 88% AM modulation with PAL-M COLOR
BAR pattern (Frequency and channel factory defined), and FM sine wave 400 Hz audio
modu-25 kHz deviation
b) Connect a oscilloscope in the output video detector and read the peak to peak burst level
signal “Vb”
c) Increment the generator frequency by 500 kHz and read the new value peak to peak burst
signal “Vh” and calculate the percentage as following:
E
H
= V
H
/V
B
d) Decrement the generator frequency by 500 kHz and repeat the procedure(c) reading the
peak-to-peak burst signal V
L
and calculate the percentage as following:
E
L
= V
L
/V
B
Minimum Nominal Maximum Unit
E
H
0,85 1 1,15
E
L
0,85 1 1,15