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Audio Amplifier Section SRX 29-SRX 30 Receiver sections
The circuit diagram shows the complete circuit and is drawn The AM and FM tuner sections are quite separate; consider
so that the various sections are clearly identified. firstthe AM section:
P.U. signals are amplified by TR 501-504 which also provide
The two-section tuning gang tunes simultaneously the iocal
frequency response correction (RIAA) for magnetic .cart-
oscillator and selected aerial coil, aerial signal current is
ridges, the resulting signal then passes through to the Input
picked up by mutual coupling to the tuned coil and fed into a
selector switch bank (Sl, S2, S3). Signals from other sources,
RF amplifier/ AGC stage TR 401 whose output feeds the local
i.e. Tape and Radio, are also fed into these switches which
oscillator-mixer input to generate an IF of 470kHz. All IF filter-
enable the desired signal to be channeled into the tone control
ing is provided by R 419, R 420, C 427 and C 429. Audio signals
stage. This consists of two "Thick Film" units (MC 483 A & B)
are fed from the detector and filter to the amplifier input selec-
which each contain: an emitter follower, followed by a voltage
tor switch bank (S1, S2, S3).
amplifier, followed by a second emitter follower; a Baxandall
type feedback tone control circuit is connected to the voltage
amplifier which also provides a phase-shift type scratch filter. VHFjFM Section
The second emitter follower has "boot-strapping" from its
emitter to its base. This network is switchable and provides a VHF aerial signals are fed directly to the RF amplifier built into
steep-slope rumble filter giving sharp attenuation below 40Hz. the LP 1186 tuner module, which is a factory pre-aligned unit,
Volume and balance controls follow on to control signal levels providing RF amplification, local oscillator and mixer stages to
into the main amplifiers. These consist of D.C. coupled generate a 10