Temperature Coefficient
Within 0.02% per
°
C.
Maintenance
No routine maintenance is required
or recommended. In case of failure,
a replacement control amplifier
should be ordered.
10.3 50 V A.C. Supply
This is provided by a step-down transformer T1, the primary of which is fed
from the a.c. stabiliser. The centre tap of the secondary winding is linked to the
chassis which is also connected to the earth pin of the mains input plug.
The 50V supply is fed through SK1 and an extension lead to the Mixer power
cableform and through SK2 to the cue Power Units and any other units which may
be mounted in the rack which houses the cue units.
10.4 Relay Power Supply
D1 and D2 provide bi-phase rectification from the 50V a.c. supply and
together with R6 for peak current limiting and C6 for smoothing constitute the relay
power supply.
10.5 Buzzer Operation
Pressing the buzzer button on the Control Room Monitor Cassette connects
together sockets 1 and 2 of Sk6 thereby operating RL1, which applies mains supply
to Sk3 for operating a mains buzzer plugged therein.
10.6 Red Light Operation
Pressing the red light button on the Control Room Monitor Cassette connects
together; sockets 2 and 3 of Sk6 thereby operating RL2 and RL3, RL2 applies
mains to SK4 for operating a mains red light circuit. RL3 short circuits the contacts
of SK5 which can be used to operate a separate relay operated, or other self
powered, system. C1 to C5 and R1 to R5 provide interference suppression.
10.7 Microphone Powering
Provision is made for powering Neumann Transistor Condenser Microphones
series f.e.t. 80 or microphones requiring a similar supply. The supply is adequate
for up to 24 of these microphones. T.2 is a transformer of the type used in the
Cassette Power Units. Here it is used to provide an earth-free 50V supply for half
wave rectification in the Microphone Power unit the circuit of which is described in
12.29. The output of this power unit is routed through SK6 and the corresponding
connecting lead to the Control Room Monitor Cassette from which it passes through
the main cableform to all the Microphone Cassettes.
10.8 Metering
Three meters are provided. A 300V moving iron meter is connected to a
switch whereby it can be connected either to the mains input or to the output of the
a.c. stabiliser. The scale has a mark at 240V and a black band extending from
210V to 250V (On early model 195V to 255V).
