Service manual

ALIGNMENT AND TEST PROCEDURES
7-6
Month 2000
Part No. 001-2004-601
7.2.6 TRANSMIT MODULATION ADJUST
1. Connect a 10 dB pad and modulation analyzer to
J402.
2. Press the "FM" and "3 kHz LPF" switches of the
modulation analyzer.
3. Inject a 1 kHz sine wave at 400 mV RMS into P100,
pin 32 on the MAC.
4. Adjust U149 with "Up/Dn" and "PgUp/PgDn" keys
for 707 mV RMS on P100, pin 29. This waveform
should be a "clean" sine wave.
NOTE: This test changes the Tx audio deviation
limit. To correct the limit, perform adjustment per
Section
7.4.6.
5. Use the "Turn on carrier" button to key the Exciter.
6. Set R446 for ±3 kHz deviation (25 kHz channels) or
±1.5 kHz deviation (12.5 kHz channels).
7. Use the "Turn on carrier" button to unkey the
Exciter.
8. Adjust U151 with "Up/Dn" and "PgUp/PgDn" keys
for a 2V P-P square wave on P100, pin 29.
NOTE: This test changes the Tx audio deviation
limit. To correct the limit, perform adjustment per
Section
7.4.6.
9. Use the "Turn on carrier" button to key the Exciter.
10.Set R425 for "best" square wave as observed on the
modulation analyzer output to the oscilloscope.
NOTE: Ensure that the oscilloscope is "DC" coupled
and the Modulation Analyzer has the 3 kHz LPF
switch set but NOT the 300 Hz HPF or 50 Hz HPF
switches set.
11.Use the "Turn on carrier" button to unkey the
Exciter.
12.Connect a 10 dB pad and modulation analyzer to
J402.
13.Press the "FM" and 3 kHz LPF switches of the
modulation analyzer.
14.Inject a 1 kHz sine wave with a level of 400 mV
RMS into P100, pin 32.
15.Adjust U149 for 707 mV RMS on P100, pin 29.
This waveform should be a clean sine wave.
16.Press the spacebar to key the Exciter.
17.Repeat Step 6.
18.Press the spacebar to unkey the Exciter.
7.3 110W POWER AMPLIFIER ALIGNMENT
7.3.1 INTRODUCTION
Refer to Figures 7-4 and 7-5 for component loca-
tions. Refer to Figure 7-9 for equipment needed and
setup diagram. Select "PA" from the "TEST" menu in
the Repeater Software.
I M P O R T A N T N O T E
No field alignment is required. Adjustments in Sec-
tions 7.3.2 and 7.3.3 are part of a new unit production
test procedure. They should only be performed as
required on "out-of-warranty" and "field-repaired"
units. Broken seals on R76, R611 or R661 will void
the warranty! Full power control range of 25-110W is
controlled by the repeater configuration parameters
under the Edit-Setup Parameters menu selection.
The adjustments in Section 7.3.2 provide for
proper matching for the output of Q501 and set a pro-
tective limit on the drive to the final transistors. This
limit is approached only under certain unusual operat
-
ing or repair conditions. However, improper adjust-
ment may impair normal operation of the PA, espe-
cially at temperature extremes.
No other adjustments are necessary in this case.
Replacement of U501, Q801, Q502 or Q503 requires
adjustments shown in Section
Figure 7.3.3 Replace-
ment of active components within the power control
circuitry of the RF Interface Board would require Sec
-
tion 7.3.3 adjustments.
These adjustments are necessary only if repairs
are made and such repairs are likely to affect the sen
-
sitivity/calibration of the forward or reverse power
detectors (e.g. replacement of detector diodes CR601/
CR651 or of the entire forward/reverse power detector