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)
provide both isolation and sufficiently low ripple for
the various amplifier stages. The 6.3v heater winding
connects through a hum adjustment potentiometer to
a positive bias voltage to minimize hum due to heater
to cathode leakage. A full wave bridge type selenium
rectifier supplies d.c. power to the speaker relays. A
tap is provided on the transformer winding to com-
pensate for aging of the rectifier.
Fixed Pod,
Etched wiring techniques are employed in the con-
struction of certain fixed attenuators, the same basic
board accommodates various circuit configurations
and resistance values. The line input pad sA TIl is a
balanced, center tapped H-type having a loss of 30 db.
The line output pad SA T12 is a
balan~ed
H-type hav-
ing a loss of 6 db. The external momtor pad 5AT13
is of the balanced L-type having a loss of 30 db.
9
Speaker Muting ond Warning Light Relays 5Kl
and 5K2
Relay SKI controls the control room speaker and
control room ON AIR light. Relay 5K2 controls the
Studio speaker and Studio ON AIR
light.
In the de-
energized position, the speakers are on and the warn-
ing light circuit is open. In the energized position,
the speakers are off, a load resistance being connected
in their place and the warning light circuit is com-
pleted. The relays are controlled by the operation of
the microphone selector switches 5S1, S52, and SS3
and the respective Program-Audition switches 5S5,
S56 and
5S7.
The relays
ar~
de-energized with the
£witches in the center (off) position and energized
in the other positions. To energize SKI, 5S1 must be
in the CR MIC position. Refer to the chart, page 15.
115V
A(;
HUM ADJ
4R9
Figure I I-Power Supply SPSI
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