Page 5 - Combined_OCR
P. 5
IF Alignment
(Using a Sweep Generator and Oscilloscope.)
RF Alignment - TM-H1
1. Couple the sweep generator into the circuit at point
using a small capacitor, (approximately 5.6pf). 1. Adjust the cores of the following coils as indicated:
2. Set the sweep marker on 13 me; it is extremely, A. The cores of L7 and L8 should be level with
important that the marker frequency be accurate.
3. Connect an AM Probe from the scope to point<^ the top of the coil form.
2. Set the RF signal generator as follows :
See Fig. 1
A. RF to the receiving frequency.
B. No modulation.
3. Connect an AC voltmeter to the speaker terminals :
TO POINT <B> A. Set the meter to the 1 volt scale.
4 Adjusting C25 and C27:
A. With no RF signal, adjust the volume control
of the receiver until the noise reaches 1 volt.
B. Increase the RF signal generator output until
TO CHASSIS the AC voltmeter decreases to 0.5 volt.
GROUND
C. Adjust C25 and C27 until the voltmeter read
ing drops to approximately 0.1 volt; then, de
crease the RF input to the receiver until the
voltmeter reads 0.5 volt again. Repeat the
4. Adjust the band pass to approximately the display process with C25 and C27 until no more quiet
ing is achieved. The RF section is now tuned
to the most sensitive point.
NOTE : There is no crystal frequency adjustment neces -
sary. Each crystal is tested at the factory for accuracy
and activity; therefore, they should be on frequency
when you install them.
RF Alignment - TM-H2
1. Adjust the cores of the following coils as indicated:
A. The cores of L7 and L8 should be level with the
top of the coil form.
2. Set the RF signal generator as follows :
A. RF to the receiving frequency of channel 1.
A. The 13 me Transformers, T4 & T5, should B. No modulation.
be adjusted for maximum gain. 3. Connect an AC voltmeter to the speaker terminals :
B. The 455KC Transformers, T6, T7, &T8, A. Set the meter to the 1 volt scale.
must be tuned to provide the band width. 4. Adjusting C19, C20, C21, C22, C23 andC24.
A. With no RF signal, adjust the volume control of
5. Repeat step 4 until maximum amplitude and proper the receiver until the noise reaches 1 volt.
band width have been achieved. B. Turn the selector switch counter -clockwise un -
til a stop is reached. This is channel 1.
6. Connect the scope (without the detector) to point C. Increase the RF signal generator output until
Adjust top slug of T9 for display as shown in the AC voltmeter decreases to 0.5 volt.
Fig. 3. (Use the innermost peak.) D. Adjust C19 until the voltmeter reading drops to
approximately 0.1 volt; then, decrease the RF
input to the receiver until the voltmeter reads
0.5 volt again. Repeat this process with C19
until no more quieting is achieved. The RF
section for channel 1 quieting is now tuned to
the most sensitive point.
E. Adjust C20 thru C24 by repeating the above
steps with the selector switch advanced to the
next position.
5. Choose the channel which comes nearest to the cen
ter frequency of the group of frequencies that you
have ordered and set the selector switch on that
channel. Repeat steps 4A thru 4D adjusting C27 for
7. Adjust the Bottom slug of T9 for maximum gain.
8. Check the curve for symmetry and amplitude as maximum quieting. C27 is on the large printed
circuit board.
shown in Fig. 3.
NOTE : There is no crystal frequency adjustment neces -
NOTE: Set generator output so "grass” is
sary. Each crystal is tested at the factory for accuracy
present on all the above patterns. and activity; therefore, they should be on frequency
DO NOT stagger tune the IF. Be sure each when you install them.
adjustment is made for maximum gain with
proper bandwidth.
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