Service manual
14
Remote Volume Options [Diagrams XL310_A4.DGM & XL310_B4.DGM].
The remote volume control is based around IC10a, IC11 and IC12b in the audio path and IC10b
in the control path. The control voltage from the external level control enters the module via
connector B pin 5 (pin 6 on ch B).
No internal clamping or range adjustments are provided.
MASTER MODULE
This module is constructed from two identical printed circuit boards, each of which contains
the circuitry for one master output, one matrix output, one auxiliary to masters summing
stage, and one half of the solo-to-masters facility [both halves are controlled by S10, however].
The following description applies equally to each half of the module, except where specific
exception is made. Each function of the module will be considered separately.
Master Output [Diagram XL320_1.DGM].
Master signals arrive via connector 'B' pins 8 and 9 [signal] and 7 [ground] at the virtual earth
summing stage IC2b, and are reinverted by IC2a before arriving at the master/solo changeover
relay RLY1, which is activated by the solo-to-masters switch S10 [which operates only if there
is a voltage on the solo gate derived from any solo/PFL switch being switched on]; this
transposes the signals from the solo and master summing stages. IC4 is the balancing network
for the insert send which appears at connector 'A' (STA) pins 19 [hot] and 20 [cold], it is
protected from excess voltage by the diode bridge D1-4, and set for maximum common mode
rejection at 100Hz by VR1 [typically 85dB]. The insert return appears at connector 'A' pins
21 [hot] and 22 [cold]; it is protected from R.F. contamination by R21/C18 and R26/C21,
and from over-voltage by diode bridge D5-8. IC5 is a differential amplifier whose common
mode rejection is factory set by VR2 to maximum at 100Hz, typically 85dB. Block b of the
insert switch S2 selects pre-insert signal from RLY1 or post-insert signal from C24 and feeds
it to block b of the master output PFL switch S3 [change to diagram XL320_3.DGM], and
via JPA to the master output fader RV1. The non-inverting buffer IC12a feeds both the meter
[via the meter changeover switch S8] and the mute switch S4. The inverting input of IC12a
is fed via connector 'B' pin 12s [solder side only] with talk signals from the communications
module. The mute switch [S4] wiper feeds the output stage IC6, which is protected from
excess voltage by the diode bridge D9-12, and set for maximum common mode rejection at
100Hz by VR3 [typically 85dB].
Matrix Output [Diagram XL320_2.DGM].
Matrix signals arrive via connector 'B' pins 10 and 11 [signal] and 7 [ground] at the virtual
earth summing stage IC7b, and are reinverted by IC7a. IC8 is the balancing network for the
insert send which appears at connector 'A' pins 6 [hot] and 7 [cold], it is protected from excess
voltage by the diode bridge D13-16, and set for maximum common mode rejection at 100Hz by
VR4 [typically 85dB].
The insert return appears at connector 'A' pins 8 [hot] and 9 [cold]; it is protected from
R.F. contamination by R50/C47 and R55/C50, and from over-voltage by diode bridge D17-20.
IC9 is a differential amplifier whose common mode rejection is factory set by VR5 to maximum
at 100Hz, typically 85dB. Block b of the insert switch S5 selects pre-insert signal from C37
or post-insert signal from C53 and feeds it to block b of the matrix output PFL switch S6