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o
cure that might occur in the exciter unit.
The
same
thing
may be said of any other piece of electronic gear.
However,
90 to
95% of all failures can perhaps be predicted with a
few possible clues listed that may help in locating the defect.
Failures or difficulties that may occur in the exciter unit
can be divided into two broad categories.
1.
Problems associated with carrier only.
2.
Problems associated with modulation of carrier.
o
o
Problems associated with carrier only can be sub- divided into
several groups.
Il•
No carrier ( no power output)
B.
Low Carrier ( power output low)
C.
Intermittent carrier
D.
Oscillation
E.
Carrier off frequency
Problems associated with carrier only will now be discussed
and possible remedies and trouble shooting hints suggested.
NO CARRIER
Of the many problems that can occur, thià perhaps is the most
serious and yet the easiest defect to find.
When this happens,
a tube has usually gone completely dead.
A comparison of test
point voltages with those given at the end of the complete tune-
up procedure,
test data sheet or voltages recorded when the unit
was working properly should reveal the defective stage.
The
difference in test point voltages with and without drive is in
the most cases quite pronounced.
When a tube has gone completely
sour or dead,
voltages noted at test points located in the plate
circuit of that particular tube will rise up to the full plate
vnitage of / 320 volts.
If the tube is drawing excessive cur-
rent,
the voltage noted at the test point will be extremely low.
A failure of any circuit from oscillator stage to power amplifier
stage will,
of course,
cause loss of carrier.
The power supply
itself should not be overlooked.
-20-
M6095 Exciter
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