Grundig TVR 3735 FR/TOP Servicehandbuch Seite 34

Description
deemphasis stage QCY03, the luminance signal passes through a
clamping stage (CLAMP), an R/P switch and the lowpass filter (LPF)
to reach the YNR stage for noise reduction and dropout compensation.
For this, the luminance signal is fed out from Pin 42, in IY02-(5 / 7) it
is delayed by one line and following the emitter follower QCY02 it is
taken via IY01-(40) to the YNR stage. If dropouts occur in the signal,
the faulty signal is replaced by the faultless delayed signal. The noise-
reduced and dropout-compensated luminance signal passes through
the non-linear deemphasis (NL DE-EM), the noise reduction stage
(DHP NC) for high-frequency noise voltages and a high-frequency
preemphasis (PIC CON). In the following "Y/C-MIX" stage the lumi-
nance signal is added to the internally fed in chroma signal. The
regenerated CCVS signal is passed through an R/P-switch, the V-
pulse insertion stage (QH/QV INS), a video amplifier (VIDEO AMP)
and is fed out from Pin 38 of IY01. Subsequently, the CCVS signal is
taken to the TV Signal Electronics stage I501-(17).
2.5.2 Signal Chassis – Chroma
Function Overview
On record mode, the 4.43MHz chroma signal is converted to 627kHz
by means of a subsidiary carrier frequency (5.06MHz).
On playback mode, the 627kHz chroma signal is reconverted into the
original 4.43MHz chroma signal by means of a subsidiary carrier
frequency (5.06MHz). The signal is amplified, added to the luminance
signal and passed on to the TV Signal Electronics circuit stage.
Record
On record mode, the signal path is the same for PAL and MESECAM
(Secam East). The CCVS signal from Frontend 2 is supplied via Pin 30
to IY01 and, passing through a clamping stage and the input selection
switch, reaches IY01-(34 / 35). From there, it is passed on to the Video-
AGC stage, an R/P-switch, the FBC stage, another R/P-switch and an
integrated bandpass (BPF 1) where the chroma signal is separated
from the CCVS signal. The chroma signal is then taken via two R/P-
switches, a gain controlled amplifier (ACC AMP) to the main converter
(MAIN CONV). In the main converter, the chroma signal (4.43MHz) is
mixed with the subcarrier frequency (5.06MHz). The converted chroma
signal (627kHz) passes through the R/P-switch, the chroma lowpass
filter (C-LPF) where unwanted mixing products are eliminated, and the
colour killer and arrives at Pin 14 of IY01. It is then fed through
IY04-(10) to the AGC stage of the head amplifier where it is added to
the Y-signal. The sum signal is passed through the record current
amplifier (CURRENT AMP), the REC/PB-switch, Pin 17 of IY04 and
plug contact PAY01-(6) to reach the headwheel.
Playback
From IY01-(15), the signal from the tape is taken via an R/P-switch to
the chroma lowpass filter where the 627kHz chroma signal is selected.
Subsequently, the 627kHz chroma signal passes through an R/P-
switch, a gain controlled amplifier (ACC AMP), and arrives 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
to the integrated chroma bandpass filters (BPF2 / BPF1). On one path,
the signal is then taken via IY01-(48) and IY02-(3) directly to the comb
filter in IY03. On another path, it is additionally inverted and passed on
via IY01-(50) and IY02-(1) to the comb filter in IY02.
The function of the comb filter is to delay the direct signal from IY02-(3)
by 2 lines periods for the PAL system (by one line for NTSC) and to add
it to the inverted signal supplied from IY02-(1). These two paths form
the so-called "comb filter" for crosstalk compensation. The chroma
signal leaves the comb filter IY02 from Pin 13 and passes through the
emitter follower QCY01 to IY01-(52). In this IC, the signal is subjected
to an amplifier stage, a lowpass filter (LPF) and the TH/COMP switch.
On MESECAM mode, this switch is set to TH and the comb filter is
bypassed. Having passed the colour killer, the NPP-stage, the chroma
bandpass filter (BPF), IY01-(46 / 45) and the CNC-stage, the chroma
signal is added to the internally fed in luminance signal in the "Y/C-MIX"
stage. The following signal path corresponds to that of the luminance
signal.
2 - 10
2.5.3 Signal Chassis – Chroma
Recording
The CCVS signal from IY01-(34) is fed through IY03-(24) to a 4.3MHz
bandpass filter for chroma signal separation. The separated chroma
signal (4.25MHz / 4.4MHz) is subjected to internal filter, control and
limiting stages and is subsequently divided down to 1.1MHz in a 1/4-
divider. The 1.1MHz chroma signal is fed out from IY03 and supplied
via IY04-(10) to the AGC-stage of the head amplifier where it is added
to the luminance signal. The sum signal is fed via the record current
amplifier (CURRENT AMP), the REC/PB-switch, Pin 17 of IY04 and
plug contact PAY01-(6) to the headwheel.
Playback
On playback, the FM signal from the tape (FMPV) is taken to Pin 21 of
IY03, the 1.1MHz chroma signal is filtered out and converted to
4.3MHz. The chroma signal (4.25MHz / 4.4MHz) on Pin 15 of IY03 is
passed on via the emitter follower QCL05 to IY01-(45) where it is
combined again in the "Y/C-MIX" stage with the internally fed in
luminance signal. The following signal path corresponds to that of the
"PAL/SECAM-BG"
luminance signal.
Record and Playback Control
IY03 is controlled via the I
Additionally, IY03-(9) is supplied with a SYNC-pulse from IY01-(37),
and a QV-SYNC from IN01-(13) is supplied to IY03-(10).
On detection of the SECAM Standard, IY03 feeds out a HIGH level
from Pin 14 which is passed on to IN01-(57).
2.5.4 Signal Chassis – Standard Sound
Function Overview
On record mode, the AF signals fed into the Standard Sound circuit
stage are supplied to the record input of IY01 and are afterwards
prepared for longitudinal track recording.
On playback mode, the AF signal obtained from the R/P-head is
amplified and then fed to the TV Signal Electronics.
Record
The AF signal coming in from the Frontend 2 is passed on from IY01-(2)
through the input selection switch, an automatic level control (ALC), a
linear amplifier (LINE AMP) and a MUTE circuit stage. The AF signal
is taken via IY01-(77), CCY63, RCY15, RCY37 / 38, CCY27 and
IY01-(79) to the integrated record equalizing amplifier (REC AMP). It
leaves IY01 from Pin 1 and is passed through plug contact PAY03-(3)
to the R/P-head. The other end of the R/P-head is supplied with the
record bias voltage of the oscillator coil TY01-(5) via plug contact
PAY03-(4).
Erase Oscillator
The free running oscillator for the full-track and sound erase head
consists of the transistor QY04 and the resonant circuit TY01 / QCY10 /
QCY47. From this oscillator also the bias voltage (BIAS) is derived.
The oscillator is operated from a HIGH level on IY01-(6) and TQCY06.
Playback
On playback mode, the R/P-head is connected to ground potential via
QCY10 / 12 and plug contact PAY03-(4) under control of IY01-(80) and
QCY09. The AF signal picked up by the R/P-head is fed via PAY03-(3)
to IY01-(7). In IY01 the signal passes through an integrated playback
equalizer (EQ AMP) and is then fed through IY01-(10) to IY01-(11).
Afterwards it is amplified in a linear amplifier (LINE AMP). The AF
signal leaves IY01 from Pin 77. Following the amplifier circuit QYC18 /
14 with line frequency rejection filter, the audio signal is routed to the
TV Signal Electronics circuit.
On "LP" playback mode, switchover of the equalizing circuit is carried
out by the switch "EQ-SW1".
Muting Circuit
The AUDIO Mute command from the deck computer IN01-(56) is used
to mute the audio outputs of IY01 in all functions, with the exception of
playback and record, and also in the case of servo faults. For this, the
IY01 obtains the AUDIO Mute command via Pin 70 (HIGH active).
TVR 3735..., TVR 3740..., TVR 5540...
"SECAM-L"
2 C-Bus, SDA on Pin 6 and SCL on Pin 7.
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