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To quickly isolate the trouble to a single general area the
following procedure could be followed. .
1.
Check to see if B
I
Z voltage exists at TP121.
2.
Check the negative voltage at TP106,
a reading of about
-35
volts here indicates
V101 thru V106 are operating properly.
3.
Check negative voltage at
TP108.
A negative reading
here from - 2 to
- 3
volts indicates that the grid of V108 is
receiving drive from previous stages.
4.
Check RF voltage at TP113 and/or TP114.
An RF voltage
here of about . 5 volts RMS indicates that there is sufficinnt
drive up to this point.
5.
Check negative grid voltage of V115 at TP118.
A read-
ing of at least - 5 volts here indictes plenty of drive and
that the grid circuit of V115 is operating.
Should all of the suggested methods fail to locate the trouble
a more thorough check will have to be made.
Reference to volt-
ages listed on the schematic diaram 852
5774
001 and to wave-
form measurements on diagrams
826
g
7991
001 and 826
7990
001 in
the back of the book may help.
Approximate RF voltage measure-
ments are also included at the end of this section.
LOW CARRIER
The same general routine used to track down the stage causing
a carrier failure can be used to check for a low carrier.
Tracing down the fault for a low carrier cnn be more elusive
though because voltages will not deviate as much from normal.
Low carrier levels are usually caused by a tube with low emis-
sion.
A slight mis - tuning somewhere along the frequency multi-
plier chain can cause low output.
Reference to the RF voltage
chart at the end of this section may be of additional help.
INTERMITTENT CARRIER
An intermittent carrier can be very difficult to track down
because about the time test equipment is set up to find the
trouble,
it disappears.
A recommended mthod finding this
is to start at the final stage ( V115)
and place a meter probe
into TP119.
Then tap on the chassis or whatever else it takes
to cause the intermittent condition.
Working back toward the
-21-
M6095
Exciter
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