The black current stabilisation system checks the output level of the 3 channels and indicates whether
the black level of the highest output is in a certain window (WBC-bit) or below or above this window
(HBC-bit). This indication can be read from the I
2
C-bus and can be used for automatic adjustment of
the Vg2 voltage during the production of the TV receiver.
The control circuit contains a beam current limiting circuit and a peak white limiting circuit. The peak
white level is adjustable via the I
2
C-bus. To prevent that the peak white limiting circuit reacts on the
high frequency content of the video signal a low-pass filter is inserted in front of the peak detector. The
circuit also contains a soft-clipper, which prevents that the high frequency peaks in the output signal
become too high. The difference between the peak white limiting level and the soft clipping level is
adjustable via the I
2
C-bus in a few steps.
During switch-off of the TV receiver, the black current control circuit generates a fixed beam current.
This current ensures that the picture tube capacitance is discharged. During the switch-off period the
vertical deflection can be placed in an overseen position so that the discharge is not visible on the
screen.
2.9.
EAST – WEST OUTPUT STAGE
In order to obtain correct tracking of the vertical and horizontal EHT-correction, the EW output stage
should be dimensioned as illustrated in Figure. Resistor REW determines the gain of the EW output
stage. Resistor Rc determines the reference current for both the vertical sawtooth generator and the
geometry processor. The preferred value of Rc is 39 kW which results in a reference current of 100 mA
(Vref = 3.9 V).
The value of REW must be:
R
EW
= R
C
* ( V
scan
/ (18* V
ref
) )
Example: With Vref = 3.9 V; Rc =39 kohm and Vscan = 120 V then REW =68 kohm
3.
TUNER
PLL tuner is used as a tuner.
UV1316 (VHF/UHF) is used as a PLL tuner. For only PALM/N, NTSC M applications UV 1336 are used as the
PLL tuner.
Channel coverage of UV1316:
OFF-AIR CHANNELS CABLE CHANNELS
BAND
CHANNELS
FREQUENCY
CHANNELS
FREQUENCY
RANGE (MHz)
RANGE (MHz)
Low Band
E2 to C
48.25 to 82.25
(1)
S01 to S08
69.25 to 154.25
