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lifier should then be reloaded for this now operating point.
Under no conditions should the power output, of the amplifier
be reduced
-
2 1
.
1 unloading the amplifier.
NEUTRÀLIZÀ.TION
o
DRIVER
The driver has been properly neutralized at the factory on the
customer's frequency.
Due to rough handling during shipment
neutralization may be affected.
Improper neutralization is
indicated by several abnormal condttions shewing up in the
operation as follows.
1.
When the ¿ rid current does not rise to maximum
with a dip in plate current as the amplifier plate
tank is tuned to resonance.
2.
If excitation is removed from the amplifier and
the P.a.. grid relay does not open.
This indicates
oscillation in the power amplifier.
This self
oscillation produces grid current which holds the
relay, K506
1
. closed;
thus, keeping the plate volt-
age applied allowing the amplifier to continue-
in self oscillation.
3.
If the balance control, R504 and R505, dœmot
enable tube plate currents to maintain a balance
within 10%.
4.
A radical change in grid current from the value given
on the Factory Test Data Sheet.
The neutralizing controls for the driver have
been brought out to the front panel of the driver
to a special machined bushing.
In the center of
this special bushing is a shaft for the machined
screwdriver slot.
It will be noted that on both
the special bushing and the internal screwdriver
shaft there are two black dots.
These two dots
are aligned in a vertical position and the neutra-
lizing capacitors are of maximum capacity.
It will
also be noted that on this special machined
bushing
is a red dot, which will appear directly opposite
the black dot on the moveable portion of the shaft.
This red dot on the special machined bushing
indicates the location of the neutralizing capaci-
tors as they were set at the factory.
These marks
will serve as a good starting place if complete
re- neutralization is necessary.
These neutrali-
zing capacitors are locked in place with a lock-
nut on the rear of the capacitor shaft.
If any of the aforementioned conditions are observed when the
unit is first placed in operation,
this indicates that reneu-
tralization is in order.
This is aecom,)lished as follows:
6/22/61
-13-
FM- 20 B
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