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Descriptions
2.7 Family Board – Standard Sound (AL)
Function Overview
On record, the AF signals fed into the Standard Sound Circuit Stage
are supplied to the record input of IC7601 and are afterwards prepared
for longitudinal track recording.
On playback the AF signal obtained from the R/P head is amplified and
then fed to the Modulator and the EURO-AV1 socket.
Record
The AF signal (AMLR) selected in the "IN/OUT" circuit stage is fed via
IC7601-(11) and an automatic level control stage (ALC) to a linear
amplifier (AMP). The AF signal is taken from IC7601-(13) via C2631,
R3612, R3613 and IC7601-(14) to the integrated record equalizing
amplifier (AMP). It leaves the IC7601 on pin 17. The AF signal is added
to the record bias current at the junction R3617 / R3618 and passed on
via the plug contact 1961-(1) to the R/P-head. The other end of the R/P-
head is connected to chassis via 1961-(3), R3600 and IC7601-(2). The
record bias voltage is adjustable with R3618 (BIAS).
For the "LP" function, switchover of the record equalizing circuit is
carried out by the switch EP CTL in IC7601.
Erase Oscillator
The free running oscillator for the full-track and sound erase heads
consists of the transistor T7609 and the resonant circuit F5603 /
C2622. From this oscillator also the bias voltage (BIAS) is derived. The
oscillator is operated from the record switching voltage "IEO" (active at
LOW level) from the deck computer IC7400-(33) and the transistors
T7606 / T7604 which follow.
Playback
On playback the R/P-head is connected to ground potential via
IC7601-(1) and the plug contact 1961-(1). The AF signal picked up by
the R/P-head is fed via 1961-(3) to IC7601-(2). The signal passes in
IC7601 through an integrated playback equalizing stage (EQ) and is
then fed via IC7601-(8) and the level control for playback R3606 (Pb-
LEV.) to IC7601-(9). Afterwards it is amplified in a linear amplifier
(AMP). The AF signal leaves the IC7601 from pin 13. After the
capacitor C2611 the signal (AMLP) is fed via the "IN/OUT" circuit stage
to the modulator and the EURO-AV1 socket, respectively.
On "LP" mode, switchover of the equalizing circuit is carried out by the
switch EP CTL.
Muting Circuit
The mute command (MTA) from the deck computer IC7400-(2) mutes
the audio outputs of IC7601 in all functions, with the exception of
playback and record, and also in the case of servo faults. For this, the
IC7601 obtains the mute command "MTA" via pin 22 (HIGH active).
2.8 Family Board – Follow TV (OS)
For the "Follow-TV" function the video signals from the EURO-AV1
(VIN1) socket are compared with the signal from the Frontend (VFV).
The resulting signal is the so-called "FOME" signal.
In the sync separators "4-C" and "4-D" of IC7850 the sync levels of
each input signal are separated from the video signals. The transistors
T7851 / T7852 form an Exclusive-NOR gate which sends a HIGH level
to the Schmitt-Trigger "4-B" of IC7850 if the sync signals are synchro-
nous. The trigger inverts the level and passes it on as a "FOME" signal
(active at LOW level) to the deck computer IC7400-(1).
2.9 Family Board – OSD (OS)
General
The IC7800 makes it possible to display a full page with separate
background (Full Page) and to insert information into the playback or
(EE) signal (Superimpose). For this purpose IC7800 is fitted with a
programmed Character-ROM containing 128 characters. The quartz
oscillator Q1820 for the background of the full page and for generation
of the sync signals (without line interlacing) operates at a frequency
which is 4 times the PAL colour carrier frequency.
The integrated Display-RAM of IC7800 allows to display 12 lines of 24
characters each. This memory reads in the character codes supplied
via the 3-lead bus IC7800-(9/10/11). Separate registers determine the
position of the display and the background. Each character consists of
a 12x18 dot matrix the vertical size of which is determined by the line
scanning pattern. The width of the character is determined by the LC
2 - 12
GV 26 EURO, GV 6000 EURO, GV 6300 EURO
oscillator at IC7800-(6/7). This oscillator operates at a frequency of
6.59MHz (±2%) and is synchronized by the horizontal pulses (CSYNC)
from IC7800-(17) when information is superimposed, or by internally
generated horizontal pulses when a full page on blue background is
displayed. Due to this method, the character read-out rate and the
background are definitely coordinated. Counters which are triggered
by the horizontal frequency and the LC oscillator are used for address-
ing the display-RAM. The integrated character-ROM converts the
character codes to pixels.
Circuit Path
The playback or loop-through signal is fed through the impedance
converter T7821 to IC7800-(15). The insertion of information into the
signal is made in the "MIX" stage. Afterwards the signal is passed
through IC7800-(13) and the impedance matching stage T7802 to the
"IN/OUT" circuit stage.
The vertical synchronization of the superimposed display is effected
externally by the field pulse "OFP" at IC7800-(20), and the "CSYNC"
signal at IC7800-(17) takes over the horizontal synchronization of the
display.
3. Keyboard Control Units (PDC... / PKG...)
The microcomputer IC7201 is the heart of the keyboard control unit and
takes over the following functions together with the corresponding
function groups:
– Evaluation of the keyboard matrix.
– Decoding of the remote control commands from the infra-red
receiver IC7203.
– Quartz clock
– Integrated RAM for storing the timer data
– Driving the display
– Bidirectional serial interface (DATD1 - pin 21, DATD2 - pin 20 und
CLKD1 - pin 19) for data communication between the keyboard
control computer and the deck computer.
– Serial interface (ODAT - pin 24, OCLK - pin 22 and OCS - pin 16)
for controlling the "OSD" circuit stage.
– I
2
C-bus (SDA - pin 77, SCL - pin 23) connecting the following
function groups with each other:
EEPROM – IC7890
Tuner/Modulator – 1701
VPS – IC7540
Input select switch – IC7552
– The drifting of the tuner or the aerial signal generates the AFC
control voltage in the Frontend circuit on the Family Board. This
voltage is supplied to pin 78 and the keyboard control computer
readjusts the tuner tuning voltage via the I
– In the case of power failures the lithium battery 2298 or C2296 /
C2297 supplies the voltage for the clock and the RAM at pin 33. The
diode D6299 prevents the lithium battery from discharging. During
power failures, a LOW level exists at pin 2 so that further functions
of the IC are switched off by the system quartz Q1298 at pins 13 / 14.
Safety precautions for lithium batteries
Warning for lithium batteries:
Lithium batteries, if incorrectly used (excessive heat, wrong connec-
tion of terminals, short circuit) represent a danger of explosion!
Lithium batteries must be replaced only by original spare parts
(see Spare Parts List). Observe the appropriate disposal regulations
for exhausted lithium batteries.
2
C bus.
GRUNDIG Service
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