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3) Take note of the position of the transformer’s wires connected to the terminal block placed on the
metal support of the transformer (U.S. version), while for the standard version the wires of the
fuse and of the switch should be unsoldered.
4) Disconnect these wires from the terminal block (only for the U.S. version).
5) Unsolder the two wires connecting the transformer with the Alarms card.
6) Disconnect the fastener of the transformer placed on the diode bridge fixed on the central chassis
of the amplifier.
7) Extract the transformer.
FAN REPLACEMENT
1) Open the top and bottom covers.
2) Remove the four screws of the front panel.
3) Slide the front panel slowly.
4) Remove the fixing screws of the fan to the two rails.
5) Break the straps of the fan’s wires.
6) Disconnect the fasteners connected to the top of the fan (some units may not be fitted with
fasteners; in this case desolder the wires).
7) Extract the fan.
INTERNAL ADJUSTMENTS
POWER SUPPLY ADJUSTMENT
No adjustments are needed after this board has been changed.
DIRECTIONAL COUPLER BALANCING (PWR MEASURE)
1) Place the DIR/REF selector (12.Fig.1) to the REF position.
2) Connect (1.Fig.2) a non inductive dummy load 50 ohm / 250W to RF output with a through
wattmeter (e.g. BIRD mod.43) in series as shown in SETUP 1.
3) Set the exciter power to obtain 250W on the through external wattmeter.
4) Now, adjust variable capacitor C2 placed on the directional coupler to obtain the minimum value
on the meter, very near to zero.
FORWARD AND REFLECTED POWER ADJUSTMENT
1) Perform SETUP 1, and increase the amplifier’s output power to 250W (on the external
wattmeter).
2) Place the DIR/REF selector (12.Fig.1) to the DIR position.
3) Adjust trimmer R9 placed on the directional coupler so that the same reading is obtained on the
PJ250 meter.
4) Switch off the amplifier.
5) Connect a dummy load 25 ohm 500W (2 dummy loads 50 ohm 250W in parallel) with a through
wattmeter (e.g.. BIRD mod.43) in series, set for the reading of reflected power (SETUP 2).
6) Adjust the drive power to minimum and switch on the amplifier again.
7) Adjust the output power of the exciter to obtain a reading of 25W of reflected power on the
external wattmeter.
8) Adjust trimmer R6 placed on the directional coupler to obtain the same reading on the PJ250
meter.
ALARMS CARD ADJUSTMENT
There are three trimmers on the Alarms card that are necessary to adjust the alarm thresholds: over-
temperature - (R4); VSWR - (R7); and overdrive - (R21).
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