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TVR 3710 …, TVR 5100 …,TVR 5500 …
Descriptions
signal is added to the Y-signal. The sum signal (FMRV) is passed
through the amplifier stage T7018 / T7019 and plug contact 1902-(2)
to the head amplifier.
Playback
Via plug contact 1902-(9) the signal from the tape (FMPV) arrives at
IC7051-(38) in the chroma circuit stage. The signal is then fed through
two R/P switches to the chroma lowpass filter where the 627kHz
chroma signal is selected. Subsequently, the 627kHz chroma signal
passes through a 6dB amplifier, a gain controlled amplifier (ACC
AMP), and arrives via a burst emphasis stage (not active) at the main
converter (MAIN CONV) where it is mixed with the subcarrier fre-
quency (5.06MHz). The reconverted chroma signal (4.43MHz) is fed
through an R/P-switch to the integrated chroma bandpass (FSC BPF).
On one path, the signal is then taken via IC7051-(24) and IC7060-(2)
directly to the comb filter in IC7060. On another path, it is additionally
inverted for PAL/NTSC and passed on via the MESECAM switch,
IC7051-(23) and IC7060-(4), to the comb filter in IC7060.
The function of the comb filter is to delay the inverted signal from
IC7060-(4) by 2 lines periods for the PAL system (by one line for NTSC)
and to add it to the direct signal coming from IC7060-(2). These two
paths form the so-called "comb filter" for crosstalk compensation. On
MESECAM mode, only the direct signal is taken to the comb filter.
Consequently, there is no other signal available for the comb filter to
add so that it is out of operation. At Pin 23, the comb filter IC7060 feeds
out the chroma signal and passes it on via pin 26 to IC7051. In this IC,
the signal is fed through a MESECAM selection switch, a lowpass filter
(LPF), an R/P switch and an amplifier stage with colour killer. Having
passed the chroma bandpass filter (FSC BPF), IC7051-(29/28), and
the chroma noise reduction (CHROMA N.C.), the signal is added in the
"Y/C-MIX" stage with the internally supplied luminance signal. The
following signal path corresponds to that of the luminance signal.
Carrier Preparation (PAL/NTSC)
– Record (PAL)
For carrier preparation use is made of a voltage-controlled quartz
oscillator (VXO) in IC7051 the oscillating frequency (4.433619MHz) of
which is determined by the quartz (Q1000) connected to pins 32 and
31. The REC-APC detector compares the phase of the transmitted
burst with that of the VXO and controls the latter accordingly. The
control voltage provided on IC7051-(33) is smoothed by C2008, R3001
and C2009. In addition, an oscillator (321FH VCO) is used which is
integrated in IC7051 and controlled by the synchronising frequency.
The VCO oscillates at a multiple of the line frequency (321f
H
) which
corresponds to a frequency of 5.015625MHz. This frequency is divided
by 8 in a 4-phase shifter. Subsequently, it is fed to the sub-converter
(SUB CONV) where it is mixed with the VXO oscillator frequency
(4.433619MHz). The result is the subcarrier frequency of 5.06MHz.
The subcarrier passes through an internal 5.06MHz bandpass (SUB
BPF) and is then fed to the main converter (MAIN CONV).
– Playback (NTSC/PAL)
On playback use is made of the quartz frequency (Q1000 –
4.433619MHz) of the free running XO quartz oscillator as a reference,
and the VCO oscillator. After reconversion of the chroma signal from
627kHz (PAL) or 629kHz (NTSC) to the 4.43MHz subcarrier frequency
the VCO is now synchronised by the burst of the played back chroma
signal. The PB-APC stage generates the control voltage for the VCO
comparing the phase of the quartz oscillator with the phase of the
reconverted 4.43MHz burst. The time constant of the filter circuit which
is connected to IC7051-(37) is determined by C2003, R3000 and
C2004. In the 4-phase shifter, the frequency is divided by 8 and fed to
the sub-converter (SUB CONV) where it is mixed with the XO oscillator
frequency. The result is, among others, the subcarrier frequency of
5.06MHz. The subcarrier is supplied via an internal bandpass filter
(SUB BPF) to the main converter (MAIN CONV).
3.6.3 Signal Chassis – Chroma
"SECAM-L"
Recording
The CCVS signal (VR) from the "IN/OUT" circuit stage is fed through
the emitter follower T7101 to a stage for chroma selection (Q5103 /
T7100). The selected chroma signal then passes through the trap
circuit (L5102 / C2102 / L5101 / C2101 / R3102) to arrive at IC7151-(29).
The trap circuit increases the selective effect of the "gaussian filter
circuit" (Q5103). Subsequently, the signal passes through a 15dB
amplifier and is then taken via pins 25 and 24 to a limiting amplifier with
a following frequency divider. Dividing the chroma signal in a ratio of
1:4 this divider generates the necessary 1.1MHz signal for recording
which is applied to pin 21 of IC7151. The bandpass which follows then
reduces the harmonics resulting from the frequency division and the
signal is routed to pin 19 of IC7151. Afterwards, it is subjected to a 10dB
amplifier and switched to pin 15. Between pins 15 and 14, the 1.1MHz
signal is fed through an "anti-gaussian filter circuit" (Q5108). The signal
is limited then in IC7151 and passed via pin 17 to the adjustment control
for the SECAM chroma recording current, R3027 (SECAM-CURR.), to
the junction R3027 / R3023 where the signal is added to the Y-signal.
The sum signal (FMRV) is taken via the amplifier stage T7018 / T7019
and plug contact 1902-(2) to the head amplifier.
Control of the switches in IC7151
On recording, a LOW level (0.7V) is present at the collector of the
transistor T7105. This transistor works like a diode, turns on and
applies approximately 1.3V to IC7151-(23). From this level, the follow-
ing detection stage can identify the recording mode and switches all in-
circuit switches to record position.
Playback
On playback, the "uncontrolled FM signal from the tape" (FMPV) is
taken to pin 23 of the IC7151 and is then amplified by 6dB. From pin 21,
the signal is fed via a bandpass to IC7151-(19). Between pins 19 and
18, the obtained 1.1MHz signal passes through a 10dB amplifier; via
pin 16, it is fed to another amplifier in IC7151 whose feedback path
contains an "anti-gaussian filter circuit (Q5108)" which is connected
between pin 14 and pin 16. In the AGC stage following the amplifier,
the signal undergoes an automatic gain control (AGC) and its fre-
quency is doubled (2.2MHz) in the full-wave rectifier "RECTIFIER f x2.
From IC7151-(10), the 2.2MHz signal is fed to the bandpass
(R3126…R3127) which removes disturbing harmonics from the wanted
signal. In another doubling stage which obtains the 2.2MHz signal from
IC7151-(8), a 4.4 MHz signal is generated. This signal is subsequently
amplified by 10dB and is fed to the colour killer via pin 31, the anti-
gaussian filter circuit (Q5100) and pin 32. From IC7151-(1) the 4.4MHz
signal is fed into the bandpass (R3122…C2121) which separates
disturbing harmonics from the wanted signal. The resulting SECAM
chroma signal is taken via the impedance converter T7106 to
IC7051-(28) where it is added to the CVS-signal.
3.7 Signal Chassis – 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 TV Signal Electronics and the EURO-AV socket.
3.7.1 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 C2611,
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 1901-(1) to the R/P-head. The other end of the R/P-
head is connected to chassis via 1901-(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.
3.7.2 Erase Oscillator
The free running oscillator for the full-track and sound erase heads
consists of the transistor T7603 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 "IREC" (active
at LOW level) from the deck computer IC7410-(9) and the transistors
T7606 / T7605 / T7604 which follow.
3.7.3 Playback
On playback the R/P-head is connected to ground potential via
IC7601-(1) and the plug contact 1901-(1). The AF signal picked up by
the R/P-head is fed via 1901-(3) to IC7601-(2). The signal passes in
IC7601 through an integrated playback equalizer (EQ) and is then fed
via IC7601-(8) and the level control for playback, R3606 (PB-LEVEL),
to IC7601-(9). Afterwards it is amplified in a linear amplifier (AMP). The
AF signal leaves the IC7601 from pin 13. After the amplifier circuit
IC7608 with line frequency rejection filter, the signal (AMLP) is fed via
