Daewoo 2898ST Service Manual page 23

No Name
43 PHI-1 FILTER
44 GROUND
45 EAST-WEST DRIVE
46 VERT DRIVE +
47 VERT DRIVE -
48 IF INPUT
49
50 EHT/OVERVOLTAGE
PROTECT INPUT
51 VERT
SAWTOOTH
CAPACITOR
52 REFERENCE
CURRENT INPUT
53 AGC
DECOUPLING
CAPACITOR
54 TUNER AGC
OUTPUT
55 AUDIO
DEEMPHASSIS
56 DECOUPLING
SOUND
DEMODULATOR
Description
The loopfilter connected to pin 43 is suitable for various signal conditions as
strong/weak and VCR signal.
This is achieved by switching of the loopfilter time constant by changing the
PHI-1 output current.
Via I2C bus FOA/B, different time constants can be chosen, including an
automatic mode which gives optimal performance under varying conditions.
To this pin are connected the IC-substrate and horizontal output.
The EW drive is a current output.
The output is single-ended and is fed directly to the EW-input terminal
The vertical drive has a current output. The output is balanced which ensures
a good common mode behavior with temperature and makes the output signal
less sensitive for disturbances.
The PLL frequency range is 32-60MHz with corresponding VCO frequency
64-120MHz.
The IF input impedances is 2
load for commonly used SAW filters.
A DC coupling is allowed, so no series capacitors between SAW filter and IF
input are necessary.
The input range for EHT tracking is 1.2 ~ 2.8V, for a compensation of +/- 5%
on vertical and/or EW.
The tracking on EW can be switched on/off by HCO.
The overvoltage protection is activated when the voltage on pin 50 exceeds
3.9V typical.
This pin requires a capacitor to ground of l00nF +/- 5%.
The optimal sawtooth amplitude is 3.5V and is determined by the external
capacitor and charge current.
The sawtooth bottom-level is 2V.
This pin requires a resistor to ground.
The optimal reference current is 100 . which is determined by this resistor.
The AGC capacitor value is 2.2
compromise between AGC speed and tilt for all AGC modes
(negative/positive modulation).
This output is used to control (reduce) the tuner gain for strong RF signals.
The tuner AGC is an open collector output which is acting as a variable
current source to ground.
not used.
This pin requires a capacitor of 10
The pin acts as a low pass filter needed for the DC feedback loop.
23
in parallel with 3pF and matches the required
and has been defined for an optimal
connected to ground.