volts depending on the particular needs of
the transmitter and frequency.
TheprimaryoftheLowVoltagetrans-
former should be tapped correctly in order
toproducethedesiredoutputfromthe+/-20
volt section.
A convenient place to measure both volt-
ages is at the fuses on the PDM Generator.
Use a suitable voltmeter to measure the
+/-20 volt supply. Measure each voltage
with respect to ground. If the voltages are
under 19 Vdc, disconnect AC power and
re-tap A20T1 to the next lower primary
voltage (taps 240, 0).
It is desired that the low voltage supply be
between 19 and 23Vdc both plus and minus.
Use a procedure of removing AC power, tem-
porarily safety grounding transformer taps,
moving the primary wiring to the next lower
increment, then measuring +/-20 volt sup-
plies, to achieve the desired supply voltages.
Note: The transformer tap connections
are provided on TB3, terminals 15 through
19. Refer to Figure 2-3 for instructions on
using the Wago block terminals. Move the
AC connection as deemed appropriate to
achieve the desired output voltage.
3.3.5. High Voltage Supply Adjustment
TheHighVoltageSupplyreadingonthe
multimeter should be in the range of 250 to
265 volts for normal full power operation.
Significantly less than this will sacrifice
positive peak modulation if operating at or
near the transmitter’sratedpower.Signifi-
cantly higher than 265 volts will result in
Supply Voltage overloads.
WARNING
ENSURE ALL VOLTAGE IS REMOVED
FROM TRANSMITTER AND ALL POINTS
WHERE VOLTAGE HAS BEEN APPLIED
ARE GROUNDED BEFORE CHANGING
ANY TAPS ON THE TRANSFORMER.
Ifthe HighVoltagereading istoo high,the
transformer primary needs to be changed to
a higher setting.
If the High Voltage reading is too low, the
transformer primary needs to be changed to
a lower setting.
The Supply Voltage can be changed in
approximately 5% increments by changing
to the next tap position.
3.3.6. RF Drive Measurement
WARNING
ENSURE THE HIGH VOLTAGE IS TURNED
OFF BEFORE PROCEEDING WITH THE
FOLLOWING STEPS.
Measure the actual RF drive level with a
scope connected to a PA module. Place the
oscilloscope probe across R13 or the
equivalent terminal of any module.
Attach the probe ground lead to the RF
drive ground plane. Do not use the cabinet
or chassis ground as this will give an incor-
rect waveform. Proper drive level should be
26-32 volts peak to peak on all eight inputs
ofeachPAmoduleA1,A2,A3,andA4,with
high voltage OFF.
If the RF Drive exceeds 32 volts peak to
peak, the tap settings on the low voltage
transformer will have to be changed.
WARNING
ENSURE ALL VOLTAGE IS REMOVED
FROM TRANSMITTER AND ALL POINTS
WHERE VOLTAGE HAS BEEN APPLIED
ARE GROUNDED BEFORE CHANGING
ANY TAPS IN THE FOLLOWING STEP.
To checkifthe primary isproperlytapped,
it is advisable to measure the +/-20 volt
supply on the PDM Generator. Measured at
the fuses, it should be in the range of 19 to
23 volts. If too high, change the primary
setting of A20T1 to a higher position (for
example, from 240/0 to 240+11).
If the primary setting is proper, but the RF
drive level produced by the IPA is too high,
the secondary taps on A20T1 will have to be
changed to a lower number to reduce the IPA
Figure 3-3. Cabinet Top with Output Network Removed
3-4 888-2314-001 Rev. AD
WARNING: Disconnect primary power prior to servicing.
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