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  4. HF-2500DX
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QRO Technologies HF-2500DX Instruction Manual

Summary of HF-2500DX

  • Page 1

    Qro hf-2500dx linear amplifier qro hf-2500dx linear amplifier instruction manual qro technologies, inc qro technologies, inc 1117 west high street p.O. Box 939 bryan, oh 43506 usa tel & fax: (419) 636-2721 e-mail: sales@qrotec.Com internet: http://www.Qrotec.Com publication date: october 1996 copyri...

  • Page 2: Specifications

    2 specifications band coverage: 160, 80, 40, 20, 17, and 15 (12 & 10 export only) meter amateur bands. 12 & 10 meter also useable in usa with proof of license and user modification. Drive power required: 50 to 60 watts nominal for rated output maximum output power: 1,500 watts peak all modes includi...

  • Page 3: Table Of Contents

    3 table of contents warranty 4 proprietary notice 4 safety notification 5 unpacking & inspection 6 reshipment instructions 6 top cover removal 6 transformer & tube installation 6, 7 line voltage selection power block wiring 7 introduction 7, 8 location 8 ac power line considerations 8, 9 antenna 9 g...

  • Page 4: Warranty

    4 warranty _____________________________________ the hf-2500dx is warranted against defects in material and workmanship for a period of two years for the original date of sale. This warranty does not cover the gu-74b (4cx800a) tetrodes which carry a separate one year warranty. During the warranty pe...

  • Page 5: Always Think

    5 always think safety __________________________________________________ this linear amplifier described in this manual contains voltage hazardous to human life and safety which is capable of inflicting personal injury. Never operate the amplifier with the top cover removed and the top cover safety ...

  • Page 6

    6 unpacking and inspection the amplifier is shipped in three cartons: amplifier, plate transformer, tubes/control transformer. Before unpacking each carton, check the exterior of the shipping carton for any sign of damage. All irregularities should be noted. Unpack and remove each component carefull...

  • Page 7

    7 viewed from the front of the amplifier. Carefully place the plate transformer into the power supply compartment cavity between the blower and the circuit board stack located behind the front panel meters. Align the transformer with the chassis mounting holes and secure it to the chassis with at le...

  • Page 8

    8 which can deliver adjustable output power from 0 to 100 watts. A grid driven input circuit using a 50 ohm 100 watt non-inductive shunt resistor feeds each 4cx800a tetrode tube which are connected in a grounded cathode configuration. An alc circuit develops negative voltage that can be fed back to ...

  • Page 9

    9 house wiring circuit, as the ratings of the wire will almost certainly be exceeded. Avoid excessively long runs of wire between your service entrance and the amplifier. A heavy flow of current in such a line results in a voltage drop which can affect the performance of your equipment. No plug is s...

  • Page 10

    10 rf out connect this socket to the cable coming from your antenna. Note: use shielded cable, such as audio-type cable, for the following connections. Key xmt connect this socket to the t/r relay socket on your transceiver. This connector requires contacts that are normally open in the receive mode...

  • Page 11

    11 fan will cool the tubes before you turn the amplifier off. Reading the meters r efer to front panel pictorial while you read the following information: multimeter: the multimeter switch on the front panel of the amplifier directly below the two panel meters selects the right-hand meter functions....

  • Page 12

    12 fault light/switch: if you amplifier is operated in such a manner to produce excessive screen grid current, a protection circuit will place the amplifier in a standby mode. A red light will light in the fault switch. The amplifier can be reset into a transmit mode by pushing the red switch. A suc...

  • Page 13

    13 tune up procedure before making any tune up procedures, make sure your amplifier is connected to an appropriate load capable of handing at least 1,500 watts of power. Failure to do so may result is serious damage to your amplifier. When the two minute warmup cycle has been completed, the red powe...

  • Page 14

    14 5. Turn the load control counterclockwise, and the screen current should start to fall. Continue to turn the load control counterclockwise until the screen current reads 25 ma. 6. Turn the tune control clockwise until the screen current reads between 50 - 100 ma. Again, turn the load control coun...

  • Page 15

    15 18.10* 21.30 24.90* 28.50 *transceiver's tuner used a word about wattmeters: the most reliable and accurate wattmeters are either the bird or coaxial dynamics thru feed. Wattmeters which use a ferrite core for r.F. Sampling can be unreliable at high power levels. If you are using such a wattmeter...

  • Page 16

    16 feature after your amplifier has been properly tuned. Periodic maintenance make sure the amplifier has been disconnected for the ac power source and the high voltage filter capacitors have bleed down to zero. Remove the top cover from the amplifier at least once a year and remove the dust. Dust a...

  • Page 17

    17 multimeter inoperative in plate current function 1. Resistors r311 lv & bias pcb 2. Switch sw401a&b meter switch pcb 3. M-1 multimeter 4. F303 2 ampere fuse multimeter inoperative in screen voltage function 1. Components on screen supply pcb a. Capacitors c401 or c402 b. Diodes d401, d402 c. Resi...

  • Page 18

    18 amplifier will not key when transceiver is keyed to transmit 1. Components on lv & bias pcb-260 a. Fuse f301 b. Bridge rectifier d301 c. Capacitor c301 2. Resistors r305, r306 3. Operate/standby sw4 front panel 4. Components on rf i/o switch pcb a. R601, r603, r604, r606, r607 b. Relay ry1 c. C60...

  • Page 19: Circuit Descriptions

    19 two minute warmup cycle not functioning components on lv & bias pcb 1. U3 555 timer and related components 2. Transistor q1 3. K3 relay circuit descriptions refer to the appropriate schematic diagrams and pcb layouts while you read the following paragraphs. Power supply power transformer t1 suppl...

  • Page 20

    20 resistor r209 is a protection resistor connected in series with the plate voltage circuit. If a short develops, this resistor prevents the b- from rising to the b+ potential. Thus providing protection for all the components within the b+ circuit including the 4cx800a tetrodes. Resistors r110 - r1...

  • Page 21

    21 (transmit mode). Ry2 closes and the rf energy supplied by the transceiver passes though ry2's closed contacts to relay ry3. If you have selected 160, 80, or 40 meters on the band selector switch sw3, the signal passes through normally open contacts and to r607 the 50 ohm 100 watts input swamping ...

  • Page 22

    22 your transceiver. Capacitors c608 & c609 form a voltage divider that couples some of the rf driving voltage to diodes d604 & d605. When the rf driving voltage exceeds the alc threshold, the diodes rectify the negative half cycles. Capacitor c610 filters and bypasses this voltage, while resistor r...

  • Page 23

    23 across r602 and ry1. 12 vdc is then dropped across ry2 and r603. The remaining +62 vdc is dropped across resistor r604. Capacitor c601 and resistors r601 & r602 plus diode d602 form a break make delay circuit for ry1 & ry2. This helps to make the proper latching and unlatching sequence for relays...