Function Overview - Grundig TVR 3735 FR/TOP Servicehandbuch

TVR 3735..., TVR 3740..., TVR 5540...
The vertical deflection current flows from one half of the bridge output
stage within I501-(7) through the vertical deflection coils and the
measuring resistor R304 to the other half I501-(4). For attenuating and
suppressing the horizontal deflection signals resulting from crosstalk
from the horizontal to the vertical deflection coils, C310 and R306 are
connected in parallel with the vertical deflection coils.
The picture height, picture position and the linearity are adjusted by the
software.
2. Signal Chassis
2.1 Signal Chassis – TV Control (CO)
The microcomputer I701 is the heart of the TV control and takes over
the following functions together with the corresponding function groups:
– Evaluation of the keyboard matrix via I701-(33 / 34)
– Decoding of the remote control commands from the infrared
receiver IQ01 via I701-(36)
– Bidirectional serial interface (SYS Dout - Pin 40, SYS DLK - Pin 41
and SYS Din - Pin 44) for data communication between the keyboard
control computer and the deck computer.
– I C-bus (SDA - Pin 3, SCL - Pin 4) connecting the following func-
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tion groups:
TV Tuner – U101
VCR Tuner – U102
TV Signal Processor – I501
– ROM I C-bus (ROM SCL - Pin 7, ROM SDA - Pin 8) connecting
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the EEPROM I703.
In the EEPROM the keyboard control computer (I701) stores special
data of the customer and the machine (eg. station tuning data/
channels, software/adjustment values). The data is transferred via
the I C-bus (SDA / SCL).
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– Chroma standards switching (optional) for tuner U101 is effected
via the following pins:
Pin 1 (SECAM-L´1) – SECAM-L - Band I
Pin 17 (TV/AV AM/FM) – AM/FM/Video Sound
For tuner U102 (optional) the switching of chroma standards is effected via
the following pins:
Pin 2 (SECAM-L´1) – SECAM-L - Band I
Pin 18 (TV AM/FM) – AM/FM Sound / PAL-BG/SECAM-L
– The drifting of tuner U101 or of the aerial signal produces the AGC
control voltage in the Frontend circuit of the TV-Signal Electronics at
I501-(53). This voltage is supplied through QC701 to Pin 32 and the
≤ P readjusts the tuner tuning voltage via the I
– The drifting of tuner U102 or of the aerial signal produces the AFT
control voltage in Frontend 2 at I201-(15). This voltage is supplied
to Pin 31 and the ≤ C readjusts the tuner tuning voltage via the I
bus.
– The PAY-TV signal path is enabled via Pin 16 according to the
selected programmes.
– The EHT section is activated first via Pin 9 with a HIGH level and
second with a LOW level at Pin 43. The beam spot suppression is
enabled by means of a HIGH level applied to Pin 43 when switching
off.
– Muting of the loudspeakers is realised by means of a HIGH level
supplied through QC601 to Pin 20.
– For on-screen-display of information and in teletext mode, the
keyboard control computer feeds out the blanking signals (Pin 47 -
RED, Pin 48 - GREEN, Pin 49 - BLUE and Pin 50 - BK OUT). The
oscillator circuit for the internal column counter is located between
Pin 38 and Pin 39. For synchronising the inserted display, for
determining the appropriate position of the individual pixels on the
screen, the horizontal and vertical synchronising pulses are fed
through Pins 45 and 46 to the character generator within the
keyboard control computer.
For teletext operation and for VPS/PDC programme scanning, the
CCVS signal is supplied to Pin 30 of the ≤ P. The corresponding data
is selected from this signal and processed for RGB output or for VPS/
PDC programme scanning.
For line interlace suppression in full page teletext mode, the
vertical deflection is modulated with 25Hz via Pin 52.
– For VPS/PDC programme scanning the keyboard control computer
takes up a scanning mode if two and more VPS/PDC transmissions
have been preprogrammed. For this, the computer tunes the tuner
at certain intervals and for a short time to the respective TV stations
to read out the current VPS data. This is to ensure that the computer
detects also transmissions for which the TV stations have fixed an
earlier broadcasting time than originally planned, and that the video
recorder is controlled accordingly.
GRUNDIG Service
2.2 Signal Chassis – Deck Control (DE)

Function Overview

Deck control is effected by the deck computer IN01 together with the
microcomputer I701. Data communication between the two microcom-
puters takes place via the bidirectional serial interface SYS Dout /
SYS Din / SYS CLK (Pins 68, 69, 71). Additionally, the deck computer
is provided with a I
Chroma/Standard Sound) and IY03 (SECAM L).
The deck computer is a microcomputer especially developed for video
recorders. The operating system is stored in the integrated mask-
programmed ROM of the ≤ C. The computing speed is determined by
quartz XNC02. Quartz XNC01 determines the clock frequency of the
integrated clock.
In the case of a power failure the capacitor CN59 provides the supply
for the clock and the RAM (for timer data) at Pin 37. The diode DN02
prevents the capacitor from discharging. During the time of the power
failure, a LOW level exists at Pin 5 (POWERFAIL) so that further
functions of the IC are switched off by the system quartz XN02 at Pins
38 / 39.
The deck computer is responsible for driving and checking the tape
deck including the servo systems for the tape transport and headwheel
control. It also controls the power supply stage, the light emitting
diodes, record/playback switching process, audio mute, and the re-
lease of the recording currents.
Via Pin 14, the deck computer receives the remote control commands
from the infrared receiver IQ01 for controlling the video functions.
The deck control consists of the following function groups:
– Reset and Activation of the Power Supply Stage
– Loading Motor Control (loading / threading mechanism)
– Winding Tachopulse Processing
– Beginning of Tape / End of Tape Detection
– Head Servo Control
– Tape Servo Control
– Tracking / Autotracking
Reset and Activation of the Power Supply Stage
When connecting the TVR to the mains, IN02 generates the low-active
switch-on reset pulse. This pulse is applied once to the deck computer
IN01-(43).
Via Pin 55 on the Power Chassis, the deck computer controls Q803
and the RLY01 relay. The switching contacts of the relay are used to
supply the mains power supply stage with voltage.
Loading Motor Control (loading / threading mechanism)
2 C bus.
The loading and threading mechanism is driven by the threading
motor. For driving the loading motor, the deck computer IN01 feeds out
the control signals LM LOAD (Pin 44) and LM UNLOAD (Pin 45).
C
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These signals drive the loading motor via the loading motor driver
IN03-(5 / 6, 2 / 10) and plug contacts PAN01-(1 / 2).
The ≤ C detects the position of the tape deck by the function selection
switch and the start of tape/end of tape sensors. The function selection
switch is connected with the deck computer IN02-(30...33) via the
plug-in connection PAN01-(4...7).
Winding Tachopulse Processing
The optocouplers (SN01 / SN02) on the left and right reel produce
pulses when the reels are turning. These pulses are directly routed to
IN01-(82 / 81).
Beginning of Tape / End of Tape Detection
To identify the beginning of tape and end of tape, the VHS cassette has
a clear foil, 13 -19cm long, on each end of the tape. The beginning and
end of tape is identified by two optocouplers. For this purpose, the
transmitting diode is inserted into a hole in the middle of the cassette.
The phototransistors are located at the outside, left and right, of the
cassette. The phototransistors SN03 (beginning of tape) or SN04 (end
C-bus (Pins 59, 60) for controlling IY01 (Video/
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MODE CAM A CAM B CAM C CAM D
EJECT L H H H
STAND BY L H L H
REV H H L H
STOP H H L L
PLAY H H H L
SLOW H L L L
BRAKE H L H H
FF/REW H L H L
CAM OFF H H H H
Description
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