Hammarlund FM50A - Receiver Alignment Procedures

(c) With the micro-ammeter now connected from terminal 4 of J105 to ground, adjust
L1l6 and L1I5 for maximum indication. (position 4 of recommended test meter)
(d) With the micro-ammeter now connected across terminals 5 and 7 of J105, adjust
C159 for maximum indication. The value of shunt R153 is such that a micro-
ammeter with an internal resistance of 2000 ohms will actually read 10 milliamperes
at full scale. When making this adjustment, a minimum of 2.5 milliamperes should
be obtained. (position 5 of recommended test meter)
(e) With the micro-ammeter connected across terminals 9 and 10 of J105, C154 and
C153
should be adjusted for maximum radio frequency output as indicated on the
dummy load. The value of meter shunt R149 is such that the micro-ammeter will
read 200 milliamperes full scale. When making this adjustment, the final plate
current should not exceed a value of 160 milliamperes. Excessive loading as indi-
cated by abnormally high plate current may be corrected by increasing the spacing
(decrease coupling) between L1l2 and L1I3.
(f) Neutralization should be checked by removing the crystal from its socket Y201,
With the crystal removed, the grid current of the final radio frequency stage should
be zero. Rotating the plate tuning condenser C154 should not produce any grid
current or radio frequency output. This test should be made with the final stage
shield in place.
(g) Mter making the above adjustments, the transmitter frequency should be set against
a known standard. This adjustment is C183 associated with the crystal oscillator
stage V1I3A.
(h) Mter making the previous adjustments the deviation should be adjusted by applying
a 1000 cycle tone of 1. OV rms amplitude to the microphone connector J104.
Potentiometer R172 should be adjusted for ±5 Kc deviation as indicated on a devia-
tion meter. This adjustment should always follow step (g) above.
CRYSTAL MULTIPLICATION
The following information is listed as a guide which will be helpful when retuning a
transmitter from one end of the band to the other.
Crystal Frequency, L118
2X
Crystal Frequency, L1l7
6X Crystal Frequency, L115/L1l6
12X Crystal Frequency, C159/C160
12X Crystal Frequency, (Carrier) C153/C154
NOTE - When retuning the final stage it is suggested that a lOOK, 1 watt resistor be temporarily
in series with R150 and R151 to limit the plate dissipation to a safe value. A power output of 5
to 10 watts should be achievable when C159, C154, and C153 are properly resonated.
COMPLETE RECEIVER ALIGNMENT PROCEDURE
TEST EQUIPMENT REQUIRED:
1. 0-100 micro-ammeter (2000 ohms internal resistance).
2. DB audio output meter.
3. Low frequency signal generator covering 1650 KC and 10.7 MC.
4. High frequency FM signal generator covering 1363 to 174 MCS.
1. (a) Connect a 1650KC signal to pin 9 of V104A.
(b)
Connect micro-ammeter from J105 pin 3 to ground. (position 3 of recommended
test meter)
(c) Adjust top and bottom of T104 for maximum indication.
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