Harris Platinum HT EL 2000LS Technical Manual

Harris Platinum HT EL 2000LS Technical Manual Manual pdf 51 page image

c. Adjust R145 for 1.0 V at TP20.d. Set the exciter meter to EXC VIS and observe the reading.e. Using jumper JP13 and/or JP14 to set in the attenuationnecessary to bring the drive level from the exciter to 0.300watts as near as practical for 2000 watts transmitter out-put.f. Move jumper JP12 to position 1-2 to enable the AGC.g. Adjust R156 such that the transmitter output power dropsfrom 2000 watts to 1200 watts (60% of full power or -2.2dB).h. Increase the drive until the transmitter output is once again2000 watts.The exciter drive level should normally be in the range of 0.500to 0.600 watts.5.8.2 Visual Power ReductionIf one of the two power supplies in the power module should failthis circuit will adjust the drive such that the transmitter willcontinue to operate at a reduced power with the remaining powersupply.a. Preset R175 fully CW.b. Turn OFF the AC circuit breaker for one of the powersupplies.c. Adjust R175 for a visual power output of 150 watts peakof sync.d. Turn ON the AC circuit breaker and the visual powershould return to 2000 watts.5.8.3 Aural AGCa. Preset the following:1. JP3 to position 2-3 AGC out2. JP11 to positions 1-2 and 3-4 3 dB Attenuator out3. JP6 to positions 1-2 and 3-4 2 dB Attenuator outb. Turn on the transmitter ON and increase the aural drivefor 200 watts.c. Adjust R143 for 1.0 V at TP3.d. Set the exciter meter to AURAL VIS and observe thereading.e. Using jumper JP11 and/or JP6, set in the attenuationnecessary to bring the drive level from the exciter to 0.300watts as near as practical for 200 watts transmitter output.f. Move jumper JP3 to position 1-2 to enable the AGC.g. Adjust R44 such that the transmitter output power dropsfrom 200 watts to 120 watts (60% of full power or -2.2dB).h. Increase the drive until the transmitter output is once again200 watts.The exciter drive level should normally be in the range of 0.500to 0.600 watts.5.8.4 Aural Power ReductionIf one of the two power supplies in the power module should failthis circuit will adjust the drive such that the transmitter willcontinue to operate at a reduced power with the remaining powersupply.a. Preset R176 fully CW.b. Turn OFF the AC circuit breaker for one of the powersupplies.c. Adjust R176 for a AURAL power output of 15 watts peakof sync.d. Turn ON the AC circuit breaker and the aural powershould return to 200 watts.5.15.9 Component Replacement On CircuitBoardsThe circuit boards used in the VHF TV exciter are double-sidedcircuit boards with plated through-holes. Soldering on this circuitboard is possible with conventional tools if care is observed.For repair, a de-soldering station is suggested such as an Air-VacPVSG-60E De-Soldering System made by Air-Vac EngineeringCo., Inc., 100 Gulf St, Milford, CT 06460 (203-874-2541). Thisde-soldering system utilizes a venturi to develop the suction andtherefore requires an air pressure source of approximately 35 PSI.It is relatively inexpensive for such a system and works well.Techniques must be developed using the de-soldering station.Sometimes, it may be necessary to add solder to the connection toassist heat flow to the connection several times until the solder canbe removed in steps. Possibly, removing solder from both sides ofthe circuit board will assist in clearing the through-holes.The circuit board used in the VHF TV exciter utilizes plated through-holes. Because of these through-holes, solder fills the holes bycapillary action. This condition requires that defective componentsbe removed carefully to avoid damage to the circuit board.On all circuit boards, the adhesive securing the copper track tothe circuit board melts at almost the same temperature at whichsolder melts. A circuit-board track can be destroyed by excessiveheat or lateral movement during soldering. Use of a heat sourceno larger than necessary with steady pressure is required forcircuit board repair.To remove a component from a circuit board such as the typeused in the VHF TV exciter, cut the leads from the body of thedefective component while the device is still soldered to thecircuit board.Carefully grasp each component lead, one at a time with mini-ature long-nose pliers. Heat each lead independently. When thesolder begins to melt, carefully pull the lead from each hole. Theholes may then be cleared of solder with vacuum.Install the new component and solder the component in place.Section V - Maintenance888-2457-001 5-5WARNING: Disconnect primary power prior to servicing.