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FM NOISE
If FM noise exists the audio stages can be quickly eliminated
by pulling V117 froh its socket.
Noise in the audio stage can
be caused by a heater to cathode leak or a filament wire lying
near a grid connection.
Hum from the power supply or improper
regulation of the power supply can cause noise in the audio
stages.
o
If the noise is not located in the audio stages,
the next most
probable suspect is the pulse stages of V101 thru V106.
An
amplitude variation in«these stages will cause a frequency mod-
ulated noise component.
This could be caused by a heater to
cathode leak or failure of a stage to properly lirhit.
Hum from
the power supply could also cause this efficulty.
Modulation
at a 60 cycle rate can also be caused in the crystal circuit by
induction from the crystal heater.
.24 NOISE
AM noise is one fault that will not usually ,be traced to the
audio stags because an amplitude variation in the audio stages
causes an FM noise component to appear.
While this type of
.
dif-
ficulty can occur in most any stage except the audio stages, it
is most apt to prevail inme of the frequency multiplier stages
and usually near the higher frequency end of the multiplier
chain.
Hum in B/ coming from the power supply,
heater to cath-
ode leakage or an intermittent connection can cause this defect.
Hum from heater to cathode leakage will show itself as a 60
cycle component and power supply hum as a 120 cycle component.
-25—
M6095 Excitcr
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