RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-4
15 September 2003
(e)
Record difference between
TEST
meter M1
reading obtained in step (d) and digital
voltmeter reading obtained in step (b) as
TEST
meter M1's correction factor for
+
15 VOLTS
in
Established References
section of table 5-2.
5.3.2.6
-12V Check
: Check the output voltage of
modulator driver A4's -12V power supply, as
follows:
NOTE
A4TP5 is on modulator driver PWB (see figure
MD-3 to locate mod driver A4 and to MD-9 to
locate TP5).
(a)
Connect a digital voltmeter between test point
A4TP5 (-) and ground.
(b)
Digital voltmeter indication should be between -
11.0 and -13.0V.
5.3.2.7
ATU Control Check
: Check the outputs
for the associated antenna tuning unit, as follows:
NOTE
A11TB1 is located on the remote interface PWB
(A11) at the rear of the transmitter (see figure MD-
5).
(a)
Connect a digital voltmeter between A11TB1-6
(+) and ground.
(b)
Digital voltmeter indication shall be between
14.0 and 16.0V.
(c)
Connect a digital voltmeter between A11TB1-7
(+) and ground.
(d)
Digital voltmeter indication shall be between
14.0 and 16.0V.
(e)
Connect a digital voltmeter between A11TB1-8
(+) and ground.
(f)
Digital voltmeter indication shall be near 0.0V.
(g)
Connect a digital voltmeter between A11TB1-9
(+) and ground.
(f)
Digital voltmeter indication shall be near 0.0V.
5.3.3
CARRIER FREQUENCY/RF DRIVE
LEVEL AND ALARM CHECKS
: Verify the
frequency of the frequency synthesizer is the assigned
carrier frequency, confirm the RF drive level is
satisfactory and the RF drive-alarm is functioning, as
follows:
NOTE
Components with an A2 prefix on their reference
designation are located on the oscillator/RF driver
PWB (see figure MD-3 to locate oscillator/RF driver
A2 and figure MD-7 to locate specific components).
(a)
Verify the requirements of paragraph 5.3.2
have been completed, paying particular
attention to the requirements of paragraph
5.3.2.2.
(b)
Set switches or verify they are set as tabulated
for
Initial Setting
in table 4-1.
(c)
Temporarily remove the shunt post from
position ‘A’ of header E5 on the RF synthesizer
PWB A9.
(d)
Connect a variable (0 to 30 volts) DC power
supply, that has been pre-set to 30.0 volts,
between the cathode of diode A2CR3 (+) and
ground.
(e)
Set
POWER
switch S3 to
ON
.
(f)
MONITOR BYPASS
lamp DS2,
RF DRIVE
ALARM
lamp DS4,
SHUTDOWN ALARM
lamp
DS7 and
AC POWER
lamp DS10 should turn
on.
(g)
All remaining lamps should be off.
(h)
After approximately five seconds,
RF DRIVE
ALARM
lamp DS4 should turn off.
(i)
Slowly decrease output voltage of variable DC
power supply until
RF DRIVE ALARM
lamp DS4
just turns on.
(j)
RF drive alarm threshold (output voltage of
variable DC power supply) shall be between
21.0 and 25.0V.
(k)
Set
POWER
switch S3 to
OFF
.
