SUBSTITUTION OF THE PALLETS ON TV AMPLIFIERS

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Damon Glenn
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SUBSTITUTION OF THE PALLETS ON TV AMPLIFIERS 1.

1 SUBSTITUTION OF THE PALLETS ON TV AMPLIFIERS 1. Remove the amplifier module from the rack. 2. Open the cover of the amplifier module. Open the cover of the RF module (see the figure below). FINAL PALLET DRIVER FINAL PALLET CASE 1: SUBSTITUTION OF A FINAL PALLET 1. Unsolder the IN - OUT connections

pallet. Remember to rise the small parts that fix the board to the box before remove it.

2 2. Unsolder the power supply cable 3. Remove the 9 screws that fix the pallet to the box of the amplifier and remove the pallet. Remember to rise the small parts that fix the board to the box before remove it. REMEMBER TO RAISE IT ON BOTH SIDES BEFORE REMOVING THE BOARD! 4. Smear the thermal silicon paste on the rear of the new pallet you have to insert.

5. Insert the new pallet in the same position where the old pallet was

Verify the position of the resistors as indicated in the figure below.

please change the position of the two discharge resistors for the hybrids.

the board and unsolder the resistor from its position.

3 5. Insert the new pallet in the same position where the old pallet was present. Be careful to mantain the same position IN-OUT of the pallet. Verify the position of the resistors as indicated in the figure below. CORRECT POSITION OF THE MODULES OLD MODEL NEW MODEL If necessary, please change the position of the two discharge resistors for the hybrids. To make this change, you have to remove the screw that fix the resistor on the board and unsolder the resistor from its position. Remove the resistor, position it on the correct place, solder it and fix it on the board with the screw.

Connect the power supply wire and the IN - OUT

4 6. Fix the board with the screws. Be careful to fix the board lower the parts indicated in the figure below before fixing the screws. 7. Connect the power supply wire and the IN - OUT connections. Be careful not to creat short circuits in the input and output connections and to maintain enough isolation.

8. Set the trimmers indicated in the figure below to reach the minimum polarization (turn the trimmers counterclockwise completely). TRIMMERS YOU HAVE TO TURN 9.

Connect a wattmeter in series between the amplifier module and the dummy load (or the antenna). Don t connect the cable to the RF input connector (the module don t have RF power input). 11.

5 8. Set the trimmers indicated in the figure below to reach the minimum polarization (turn the trimmers counterclockwise completely). TRIMMERS YOU HAVE TO TURN 9. Connect in series to the power supply cable an analogic amperometer. 10. Connect the amplifier module to a dummy load or, if you have not it, directly to the antenna. Connect a wattmeter in series between the amplifier module and the dummy load (or the antenna). Don t connect the cable to the RF input connector (the module don t have RF power input). 11. Switch on the amplifier module and polarize the pallet at 2.2 Ampères as indicated in the figure below. To do this, turn the first trimmer clockwise until you will read 1.1 Ampères on the amperometer. After that, turn the second trimmer clockwise until you will read 2.2 Ampères on the amperometer.

12. Disconnect the amperometer and connect again the wire directly to the power connector. 13. Fix the covers on their original position and insert the amplifier on the rack. 14.

6 12. Disconnect the amperometer and connect again the wire directly to the power connector. 13. Fix the covers on their original position and insert the amplifier on the rack. 14. Connect the transmitter to a dummy load or, if you have not it, directly to the antenna and insert in series between them a wattmeter. 15. Connect a video generator to the VAM video input connector: a cable between the VIDEO OUT connector of the generator and the VIDEO INPUT connector on the rear of the VAM; a cable between CH1 connector of the generator and AUDIO 1 connector on the rear of the VAM. Use a PAL 0% field signal (black signal) to test the equipment. 16. Turn the RF OUT ADJ trimmer counterclockwise until the end. 17. Disconnect the IF IN IF OUT cable on the front panel. Connect the spectrum analyzer on the RF MONITOR output on the front panel of the amplifier unit. WATTMETER DUMMY LOAD CONNECT THE SPECTRUM ANALYZER TO THE RF MONITOR CONNECTOR

18. Switch ON the whole equipment (VAM modulator, IFC module and the amplifier). 19. Connect the cable between IF IN and IF OUT and wait about 60 seconds (soft-start time). 20.

Verify the values on the display of the transmitter, on the wattmeter and on the spectrum analyzer. 21.

7 18. Switch ON the whole equipment (VAM modulator, IFC module and the amplifier). 19. Connect the cable between IF IN and IF OUT and wait about 60 seconds (soft-start time). 20. Adjust the RF OUT ADJ trimmer to allow the transmitter to have the correct output power level (the example in the photos is related to a 1000 Wps transmitter). Verify the values on the display of the transmitter, on the wattmeter and on the spectrum analyzer. 21. Verify the voltages and the currents of the amplifier module on the display: the voltages must be about 32 V and the two currents must be one at about 34 Ampères and the other (relative at the supply unit that feed also the driver) about 38 Ampères in the case of a transmitter of 1000 Wps. ( in general we will have 17 Ampères for each pallet, 3 Ampères for the driver board of a 1000 Wps transmitter and 8 Ampères for the driver board of a 1500 Wps transmitter). DETAIL OF THE DISPLAY OF THE 1000 W TRANSMITTER

MEASURE ON THE SPECTRUM ANALYZER MEASURE OF THE OUTPUT POWER LEVEL OF A 1000 W TRANSMITTER (THE WATTMETER HAS A HEAD OF 1000 Wps) NOTE: you can read the value of the output

of the transmitter): the value will be more precise and without eventual instruments errors.

8 MEASURE ON THE SPECTRUM ANALYZER MEASURE OF THE OUTPUT POWER LEVEL OF A 1000 W TRANSMITTER (THE WATTMETER HAS A HEAD OF 1000 Wps) NOTE: you can read the value of the output power on the display on the front panel of the equipment but it would be better to make the measure with the wattmeter (with a right head adapted to the output power level of the transmitter): the value will be more precise and without eventual instruments errors. Be careful you have to made the measure of the output power level using the PAL 0% field signal and that the wattmeter always indicate the power value in Wrms that is about half of the value of the power indicated in Wps in the case of PAL 0% field signal!!!

9 CASE 2: SUBSTITUTION OF THE DRIVER PALLET 1. The procedure is the same of the substitution of a final pallet but in this case you will have to connect also the protection wires. OLD CONFIGURATION NEW CONFIGURATION

FM1-HD/FM2-HD RF Amplifier Installation and Biasing

FM1-HD/FM2-HD RF Amplifier Installation and Biasing IS05010 Original Issue 07 October 2005 Nautel Limited 10089 Peggy's Cove Road, Hackett's Cove, NS, Canada B3Z 3J4 T.+1.902.823.2233 F.+1.902.823.3183