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change are covered in the THE-1 Exciter
manual.
5.7
.1. Voltmeter
and
Ammeter
Calibration
5.7.1.1 . 500 Watt PA Chassis,
250 Watt PA Chassis
This procedure assumes that the amplifier
is in proper operating condition and that
any
problems have been resolved using the
Troubleshooting section
of
the manual for
assistance. There are three controls located
on
the Regulator
board
which
can
be
reached through the top cover. These con-
trols are for the voltage regulation and me-
tering calibrations and are factory adjusted.
No
routine alignment
of
these controls is
required unless a component was replaced
in the regulator circuit.
Equipment required for Regulator board
calibration:
a.
A voltmeter calibrated to 0.5%.
b. A clamp-
on
ammeter calibrated
to
0.5%.
c. 50 Ohm dummy load.
If a clamp-on ammeter is not available, a
suitably calibrated ammeter can be placed
in series with the +50V line to the amplifier
module. Be sure the connections are short
and tight.
5.
7.
1.1
.1. Voltmeter Calibration
The power supply output voltage is set by
R36, "Voltage Adjust", which
is
accessible
through the hole in the top cover
of
the
Amplifier chassis when is pulled out about
8". It may be necessary
to
temporarily re-
move the ground strap on the rear panel to
obtain enough cable slack to move the am-
plifier forward.
a. Connect the voltmeter between the
GND and V test points on the front
panel.
b. Adjust "Voltage Adjust" control, R36,
for a voltmeter reading of 50 volts +/-
0.1 V.
5.7.1.1.2.Ammeter Calibration
a. Connect the voltmeter between the
GND and I test points on the front panel.
b. Adjust the "ZERO" control, R60, for a
voltmeter
re
a
ding
of
0.0
volts
+/
-
. 002m V when no drive is applied to the
amplifier.
c.
Attach the clamp-on ammeter to the ser-
vice loop in the positive lead connected
to
the +50V terminal on the rear
of
the
amplifier module.
d.
Apply normal drive to the amplifier and
record the clamp-on ammeter reading.
e.
Adjust the
"I
CAL" control, R6, for a
voltmeter reading corresponding the
0.1 V per amp reading
of
d. above. i.e.,
for a 12A reading, adjust R6 for 1,20V
between the I and GND test points.
5.7.2.
Controller Calibration Alarm
and
Fault Settings
This procedure assumes that the Transmit-
ter is in proper operating condition and that
any problems have been resolved using the
Troubleshooting section
of
the manual for
assistance. The controls are all located on
the top front edge
of
the Controller chassis
and can be reached through the top cover.
These controls are factory adjusted. No rou-
tine alignment
of
these controls
is
required
unless a component affecting these circuits
has been replaced.
Equipment required for calibration:
a.
AC/DC voltmeter
b. Calibrated power meter capable
of
mea-
suring the total output power
of
the
transmitter.
c. A known good 50 Ohm load
d.
A small DC power supply capable
of8V
output@ lOmA
5.7.2.1. Manual Power Control Limit Set-
ting
This adjustment sets the maximum power
available from the Exciter in the Manual
mode.
a.
Connect the EXCITER
RF
OUTPUT
through a calibrated power meter to a
known good 50 Ohm load. Connect the
power meter as close
as
possible to out-
put connector as possible to obtain the
most accurate power measurement.
b.
Depress the FWD PWR switch on the
EXCITER front panel Multimeter select
switches.
c.
Locate and switch the APC ON-OFF
switch, S5, on the Controller top to
MAN.
d.
Turn
the transmitter
ON
and run the
PWR RAISE control to the end
of
its
range
as
indicated on the APC Meter.
AdjusttheMAN GAIN
control,Rl9,for
55W output from the Exciter.
e.
Return the Exciter
RF
OUT to its normal
connection.
f. Run the PWR LOWER down to
O
as
indicated on the APC multimeter setting
on the controller before returning the
Tr
ansmitter to service to prevent over-
drive fault.
5.7.2.2. Automatic Power Control (APC)
Limit Setting
This adjustment determines the gain of the
APC loop and the amount
of
overdrive
available in a fault condition.
a.
Connect the Transmitter
RF
OUTPUT
through a calibrated power meter to a
known good
50
Ohm load. Connect the
power meter
as
close
as
possible
to
out-
888-2312-001
put connector
as
possible to obtain the
most accurate power measurement.
b. Locate and switch the APC ON-OFF
switch, S5, on the Controller top to ON.
c. Turn the Transmitter ON and raise the
output power to 100% TPO as indicated
on
either the external calibrated wattme-
ter or the Controller
FWD
PWR multim-
eter setting.
d. Switch the Multimeter
to
APC.
e. Raise the Transmitter output power to
120%TPO.
f.
Adjust the LOOP GAIN control, R20,
for maximum obtainable reading while
using the RAISE-LOWER control to
keep the power at 120% TPO.
g. Reduce the power to 100% TPO. The
APC should indicate 80
to
90%.
5.7.2.3. Forward Power Meter Calibration
a.
Using the POWER RAISE - LOWER
switch, adjust the Transmitter output
power to the rated TPO
as
indicated on
the external calibrated wattmeter.
b.
Switch the Multimeter to the
FWD
PWR position and adjust the FWD CAL
control, R28, for 100% reading
on
the
meter.
5.7.2.4. SWR Meter Calibration
a.
With the Transmitter output running at
100%TPO:
b.
Switch the Multimeter to the SWR po-
sition.
c.
From the top cover
of
the Controller,
switch the SWR cal switch, S4, to the
CAL position.
d. Adjust the SWR CAL control, R38 for
a 100% reading on the meter. The Mul-
timeter should now have the same indi-
cation in both the SWR and
FWD PWR
positions.
e.
Return the SWR - CAL switch to the
SWR position.
5.7.2.5. SWR Foldback Trip Point Setting
After checking the calibration
of
the
SWR
meter
as
above:
a.
Switch the APC ON-OFF switch, S5, to
OFF and LOWER the Transmitter out-
put power
to
50% TPO.
b. Turn the Transmitter OFF .
c.
Temporarily remove the REVERSE
power detector slug from the directional
coupler and replace it with the
FOR-
WARD
power detector slug.
d. Tum the Transmitter
ON.
e.
Adjust the SWR TRIP control, R64,
until the VSWR FAULT led on the front
panel lights.
f.
Turn the Transmitter OFF.
g.
Replace
the
FORWARD
and
RE-
VERSE power detector slugs in the di-
rectional coupler being careful to orient
5-3
WARNING: Disconnect primary power prior to servicing.
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