structions which are a part of the B-147071
Set of Accessories for Battery operation.
If
batteries only are to be used, the battery ca
ble plug should be plugged into the power
supply receptacle at the right hand end of
the amplifier.
AC and Battery Operation
If both a-c and battery supplies are to
be
used, the five-wire a-c supply cable should be
plugged into the receptacle at the right hand
end of the amplifier unit, and the battery
supply cable plugged into Jack J2 of the a-c
unit. Selection of either a-c or battery opera
tion of the filaments and plates is then made
by operating switch D3 (plate) and switch
D2 (filament), both of which are mounted
on the a-c power unit.
To turn on the equipment, connect the
power cord to the a-c line and operate the
power switches on both the amplifier and
the power unit. The equipment is now ready
for operation.
When using batteries, the drain on the
batteries due to the volume indicator lights
is 0.3 ampere. To prolong battery life, it is
recommended that the \IOlume indicator lamp
switch be left OFF as much as possible. This
is particularly important when dry batteries
are used, since the continuous use of the
lamps will greatly reduce battery life. Fila
ment and plate batteries should be changed
when the meter indicates voltages below
"O vu" or "100" on the scale.
OPERATION
Goin Settin9s
As a general rule, the master gain control
should be operated as low as practicable
since this will result in the minimum amount
of noise. Enough latitude should be permit
ted, however, to allow for variations in sound
levels of the program.
Output Level
Normally an output level of +8 vu is ade
quate. In some cases, jt may be necessary to
transmit programs at a higher level. The
22E Speech Input Equipment will deliver
levels at +18 vu without serious distortion.
(See Figure 2.)
Precautions
The plate and filament voltages can be
checked while the equipment is in operation.
It is recommended that a close check be kept
on the condition of the batteries.
The output line keys are so connected that
when in the mid-position the program line
is short circuited. The purpose of this is to
enable master control to make loop tests
when the remote location is unattended. In
the event that more than one pickup is made
from a location where multiple extensions
of the program line are used, the line keys
"hould not be left in the mid-position since
this will disable all
of
the line extensions.
MAINTENANCE
Some tubes have higher noi:;e level:; than
others. It may be desirable to select tubes for
the first amplifier stage, although the cush
ioned socket greatly reduces trouble from
microphonic noise.
While this equipment is rugged in con
struction, it should be afforded the degree of
maintenance and inspection that any high
quality equipment would ordinarily require.
Cleanliness is essential for best opera
t
ion
and therefore the equipment should be kept
free of dust and dirt. Compressed air or a
soft bristle brush is recommended for
cleaning the apparatus. Potentiometer con
tacts should occasionally be cleaned with car
bon tetrachloride and then thinly covered
with a good grade of light mineraLoil. Excess
oil should be wiped off with a lint-free cloth.
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