Q2 OPERATION AND MAINTENANCE MANUAL 9601 64
Further input solos can be added and the reset button can be used to
cancel them. If a solo is to be cancelled from the master reset
button then a positive voltage is fed to the base of TR9 to switch it
on causing the reset line to go low. Some means must be used to
turn off TR8 as otherwise the Vdd and Vss rails would be shorted
together and TR3 is turned on to prevent this from occurring.
In the INTERLOCK position of the switch pin 1 of IC44 is also fed
to IC45 which is configured as a virtual earth mixer. Pin 7 of IC45
will thus go high and be applied to the voltage comparator IC46.
With only one solo active this comparator will not operate and the
output will remain low. When a second solo is received then pin 1
of IC44 will rise higher in voltage causing pin 7 of IC45 to rise
which in turn will cause the voltage comparator to operate giving a
reset via TR9. Of course solos can still be cancelled on the
modules on which they are active. The same is true for output
solos which enter via IC45 and are mixed with the input solos
before reaching the voltage comparator. A reset can thus be
generated by requesting another solo or by operating the master
reset.
The solo circuits on the input and output modules are a little
complex and will be explained in the relevant sections.
The second main board is the COMMS board and as the name
suggests this board handles talkback and related functions. The Q2
is fitted with a CLEARCOM communication interface which is a
three wire system carrying DC signalling and two way audio. The
PFL meter is located on this board along with the external meter
drives and their associated trimmers.
The oscillator can generate either 1kHz or pink noise whose level
can be controlled by a pot. The talkback and oscillator can be
routed to foldback, auxiliaries, groups, matrix, L/R mix and Mono
outputs. To talk to the matrix a further switch must be pressed on
the required output module.