OPERATING MANUAL EMTRON DX-3 HF LINEAR AMPLIFIER April 2005 Emtron DIVISION OF EMONA ELECTRONICS PTY. LTD. 92-94 Wentworth Avenue, Sydney 2010, Australia Tel. +612 92110988 Fax +612 92811508 www.emtron.com.
DX-3, Serial No………… INITIAL SETTINGS FOR PLATE AND LOAD CAPACITORS TEST BAND FREQUENCY FACTORY SETTINGS USER SETTINGS 50 OHM LOAD ANTENNA PLATE 28.600 MHz 10m 24.900 MHz 12m 21.200 MHz 15m 18.100 MHz 17m 14.200 MHz 20m 10.125 MHz 30m 7.070 MHz 40m 3.600 MHz 80m 1.800MHz 160m 1.850 MHz 160m 1.
TABLE OF CONTENTS 1 GENERAL DESCRIPTION..................................................................................................................................................... 5 1.1 DX-3 – INTERNAL VIEW ...................................................................................................................................................... 6 2 TECHNICAL SPECIFICATIONS ................................................................................................................
12.4 12.5 12.6 12.7 12.8 12.9 12.10 OVER-TEMPERATURE CUT-OFF ........................................................................................................................................... 20 OVER-CURRENT CUT-OFF ................................................................................................................................................... 21 IG2 BLINKS FAST - NO PLATE VOLTAGE ....................................................................................................
DX-3 LINEAR AMPLIFIER Serial No ………… OPERATING MANUAL April 2005 CAUTION The DX-3 has been designed for 100% safe operation and long life. Interlocking sensing circuitry constantly monitors conditions inside the amplifier. It must be noted however, that the high voltages present inside the DX-3 are EXTREMELY DANGEROUS. Do not remove the top cover under any circumstances if any leads are still plugged into the rear of the amplifier - especially if the AC lead is plugged in the power outlet.
1.1 DX-3 – Internal View The main components of a DX-3 amplifier are shown in the picture below.
2 TECHNICAL SPECIFICATIONS FREQUENCY COVERAGE: Complete (manually tuned) coverage of the nine HF amateur bands: 1.800 – 1.900 MHz 3.500 – 4.000 MHz 7.000 – 7.500 MHz 10.000 – 10.300 MHz 14.000 – 14.350 MHz 18.000 – 18.500 MHz 21.000 – 21.500 MHz 24.000 – 24.500 MHz 28.500 – 29.990 MHz TRANSMITTING MODES: Both continuous and low duty cycle modes are supported. That is, the DX-3 supports SSB, CW, AM, FM, RTTY and SSTV.
Five single LED’s: • on air • ready • fault • overdrive warning • SWR cut-off indicator ALC: Negative going, adjustable output level. EBS: Electronic Bias Switch - automatically switches the standing current (about 0.75 A) to a lower ("prebias") value - when there is no input drive. PRE-BIAS: A small current will flow in the tube when the amplifier is keyed on, but there is no modulation.
the 12-pin connector towards the front of the amplifier. Put the transformer in at a slight angle (about 10 degrees), so that it does not touch the section of the wire loom between the control board and the front panel display. Mind also the micro-switch, the front panel switches and the control board at the back. See picture on page 6. Move the transformer close to the front panel (do not slide it on the base plate – lift it and move).
5.2 RF connections RF INPUT The RF input is an SO-239 female connector. A 50 ohm coaxial cable line of good quality terminated with a PL-259 coaxial connector is required to connect the transceiver or exciter output to the input connector of your DX-3 amplifier. RF OUTPUT The RF output is also a female SO-239 connector. The use of a high quality RG-8A/U, RG-213 or similar 50 ohm coaxial cable line terminated with a ‘VHF’ type PL-259 connector is essential. Similarly, a VSWR of 2.6: 1 or better is mandatory.
6.2 Displays All the DX-3 indicators are concentrated in a single, solid state, “moving LEDs” display (See drawing). The following values are displayed (top to bottom): Output Power - Scale up to 4 kW, non linear. Yellow LED’s with red indicating power over 3kW. Reflected Power - Scale up to 500W, non linear. The colour is green, yellow and red, indicating progressively higher reflected power and possibly problems with your antenna. Ig2 - Zero-centred display.
7 ELECTRICAL CONNECTIONS 7.1 Connections to Transceiver / Exciter Signal connections Before making any connections, ensure that DX-3 is not connected to AC power, and the transceiver is not transmitting. Connect the antenna first to the DX-3 output. Then connect the transceiver output to the DX-3 RF input. Plug the PTT lead into the RCA socket marked PTT on the rear panel. If required, connect the ALC. (In most cases there is no need for ALC – see 10.
240 0 240V: 0 200 FAN 220 230 240 230 230V: 0 200 FAN 240 220 220 220V: FAN 0 200 220 230 240 200V: 200 FAN 0 220 230 240 Figure 3: TRANSFORMER AC INPUT CONNECTIONS 8 DX-3 DESCRIPTION 8.1 RF Section The RF section occupies the right hand side of the DX-3 (looking from the top - front). See picture in 1.1. RF Switch and tuned circuits At the front of the amplifier are two variable capacitors, for plate and load tuning.
The plate is connected to the RF network and to the choke supplying the 3400VDC voltage to the plate of the GU78B tube. 8.2 Mains transformer The transformer is the heart of the amplifier, a high performance type, designed to reduce the size and weight. It is built with a generous reserve of power, handling easily the DX-3 requirements in continuous operation. The primary can be wired for 200VAC, 220VAC, 230VAC or 240VAC operation. See Figure 3.
• Screen voltage regulator, with adjustable voltage and adjustable current limiting, for tube protection. • Overdrive protection and timer - based on detecting grid current, it initially gives visual warning and, at higher level of overdrive, it cuts off the amplifier for 2 seconds. It ensures a clean signal, making it virtually impossible to overdrive the DX-3 • SWR detector and timer - switches the amplifier to bypass mode for about 3 seconds when high SWR is detected. Adjustable SWR level.
9 POWERING UP Before switching the power on, check all the necessary connections: Earth, Antenna, Transceiver, PTT, ALC. Make sure the 2 switches on the front panel are in the positions: OFF, STBY. Switch now the mains power ON (The power switch to ON position). The "soft start" system will take about 5 seconds to fully turn the power on. SWR light will turn on briefly, then off. Wait for the DX-3 to warm up, until the READY light turns on. This takes about 2 - 3 minutes. This warm up time is a minimum.
• Repeat the above steps, while gradually increasing the input drive power, until the overdrive indicator just starts turning on. Now the DX-3 is tuned for operation at full power on that particular operating frequency. NOTES: 1. The maximum power is obtained from a DX-3 when: onset of the overdrive indication PLATE is tuned for maximum output power, maximum screen current Ig2 and minimum plate current, Ip Ig2 indicator shows 2 to 4 red LEDs. 2.
NOTE: If the output is low (say, less than about 1500W), Ig2 will never show any screen current at all. Ig2 might even indicate a negative current, in green - this is normal and is no cause for concern). However, if there (green) negative current indication, usually this will go away with better tuning of the PLATE control.
10.3 USING YOUR DX-3 While tuning and adjusting the amplifier, a CW mode is normally used. When these operations are finished, you can change to the operating mode you wish to use and start operating. 10.3.1 CW / RTTY and all digital modes In CW, the setting up of the amplifier is similar to that of the tuning mode.
The Ig2 indicator should have three to four LED's flashing on at peak of modulation. This (combined with a correct plate tuning), indicates an optimum loading, good efficiency and good linearity. A lower screen current, due to excessive loading, will reduce the output power, with an equal amount of extra power dissipated by the tube. A higher screen current, making all four LED's in the Ig2 flashing, will increase the distortion.
full power for extended periods of time, with the fan not even going to high speed. The temperature cut-off happens when the tube reaches 150º Celsius, with ample safety margin to the specified limit of 200º for the GU78B tube. 12.5 Over-current cut-off If the plate current exceeds even for a brief time a pre-set safe limit, an over-current detector will activate the power up timer, disabling the amplifier for about 2 minutes.
14 GLOSSARY AC Alternating Current ALC Automatic Level Control AM Amplitude Modulation BALUN Balanced to Unbalanced Transformer BNC Bayonet Neil-Concelman Connector dB decibel CW Continuous Wave DC Direct Current EBS Electronic Bias Switch FM Frequency Modulation HF High Frequency HV High Voltage IEC International Electro-technical Comission IMD Inter-Modulation Distortion LED Light Emitting Diode PEP Peak Envelope Power RF Radio Frequency RTTY Radio Tele Type SSB Single
15 APPENDIX 1: SCHEMATIC DIAGRAMS 15.1 DX-3 Block Diagram Vp POWER SUPPLY MODULE (See Schematic) DISPLAY MODULE & METERS Ip (See Schematic) +5V FAULT O’DRIVE ON AIR Pf H.V. DC H.V.
15.
15.3 Control Board and Adjustment Points COMPONENT SIDE VIEW The drawing below shows all the connections to the control board and the adjustment points.
Blue NEUTRAL 1 EARTH 25A 25A Yellow/Green Brown 30A 1 1 ACTIVE Blue 4.7nF/250V/Y2 4.
NEUTRAL Blue EARTH 1 25A 4.7nF/250Vac/Y2 25A 4.7nF/250Vac/Y2 Yellow/Green Brown 30A 1 1 ACTIVE 30A COVER INTERLOCK S1 K1 RELAY DPST Front Panel ON / OFF S2 Blue Brown Blue MT1 SW Yellow MT2 TRIAC Bottom View G Soft Start Module G MT2 A MT1 Brown Yellow Date: Size A4 Title MT2 1 2 3 MALE 0V Monday , January 07, 2002 Sof tStartWiring US Document Number Sheet 1 SOFT START WIRING U.S.
SWITCH 100k R10 C10 100nF C11 2.2nF 5 R8 470k/2W SS R7 470k/2W U1 R6 270k TPA C9 100nF + C8 3.3uF C12 100nF 4 SWITCH AS 1 LS 16 CS R GT 7 3 GN D 8 CL RC 6 15 PC 11 10 SSC 12 SR D SS 10k 2 VS 9 VC C SC AP 14 R9 C7 47nF 13 R4 150/2W C6 2.2nF + C5 220uF/25V 220/2W R3 C4 220uF/25V 28 1N4007 GATE 100/2W 100/2W D2 R1 R1 C1 Date: Size A4 Title Monday , January 07, 2002 Document Number SOFTSTART240V SOFT START E M T R O N Sheet For 110VAC, replace C1 by 3.
15.7 Circuit Diagram – QSK JP1 1 2 D5 + 1N4004 D3 D1 1N4004 1N4004 + R2 2.
15.8 Circuit Diagram – RF MODULE NOTE: R1 changed to 680 ohm R.F. OUT MODULE (Simplified Diagram) C14 PLATE CHOKE PLATE VOLTAGE 2200pF C1 1000pF/6kV C2 1000pF/6kV C3 1000pF/6kV RS1 PROTECTION BOARD Lp 100 D5 A106 R3 100 75k EG2 (BLUE) C5 2.2nF R2 100 MOV4 140V D4 A106 D3 D2 A106 R1 A106 100 D1 A106 V1 GU78B SCREEN C13 D1 3k 10nF/1kV 1N4148 R3 D2 10 MOV1 140V 1N4148 C8 1500p SM MOV 140V R4 3.9k/2W C9 MOV3 140V 22nF 2.2nF C10 BIAS 22nF C11 2.
X3-13 1 VR3 2 VV+ 2 3 2 V- L74 L73 L72 L71 L75 L76 L77 L78 G G G G R R R R Ig2+ 1 VR6 V- L41 L42 L43 L44 L45 L46 L47 L48 L49 L50 G G G G Y Y Y Y R R U6 LM3914 V+ 5k V+ 3 R13 2k2 SWR/FLT FAULT C7 2.2nF REFLECTED POWER TX 5k R5 2k2 31 OD/T X 3 R2 1k2 C12 VR2 1nF 50k R12 2k2 VR4 X3-6 1 C10 2.2nF L81 R X3-7 C11 2.2nF 1 L79 G 3 X3-10 1 C14 2.
5K POT4 RFIN X6. 3 X2.5 GND WO6 C34 R47 C11 100nF 2K2 GND 50K Q8 T9 GND D29 D29 WO6 1 2 3 R36 7 U1 3 + 100K C37 4.7nF LM358 - 6 + 5 220k R29 8k2 R69 GND T10 GND BC557 Q9 4 3 Q7 MPSA92 (4=GND, 8=12V) U14 U12 OUT 10uF SW1 1 OUT R73 Q18 BC557 12V GND C2 C1 400 2(4=GND, 8=12V) GND C26 BC547 1 2 3 1N4007 4.7nF C43 Q16 GND C35 T8 R27 4K7 C3 100nF R26 1K GND F2 300VAC2 POT3 BC557 GND C9 12K T7 R35 100VAC2 BR2 100VAC1 X2.6 F3 X7.
R78 R8 D14 POT5 R71 X1. R13 R12 D10 R28 R50 R49 R51 R52 R34 R30 R75 C27 SWR 1 R32 R31 R37 R33 PRE-BIAS C48 1 C39 1 R41 U1 Q18 C3 R27 R26 R73 1 C37 C30 D24 1 R29 POT7 R69 1 Q6 C50 R84 D33 R86 Q2 R87 1 1 C28 C29 D32 R83 R74 U2 R91 C26 R88 R56 R85 D15 Q7 U3 U4 C5 + + EBS SW2 SW1 R15 Q4 Q1 U8 C43 R5 U13 X8. U9 1 C31 U10 1 C18 D27 D28 D3 D2 C32 BR1 1 AMPC v.3D X2.
Control Board – Solder Side Track work AMPC V.
16 APPENDIX 2: WAVEFORMS 16.1 QSK (Optional module) Switching Fig. 4 No “Hot switching”: The output relay (Top trace) switches first, then the RF drive is applied (Bottom trace) 16.2 Linearity V a=-1674mV,b=1958mV V 21Apr2003 18:36 Fig. 5 Sample of linearity curve obtained on a DX-3 at 4000 W PEP output, by using a two-tone generator and a PC oscilloscope in XY mode.
17 APPENDIX 3: ADJUSTMENTS ADJUSTMENTS TO EMTRON “DX” AMPLIFIERS CAUTION Most of the following adjustments require the amplifier to be open and powered up. This also implies defeating the mains interlock safety switch, which is extremely dangerous since high voltage / high power DC and AC and RF voltages are exposed. We do not recommend anyone to do this, since extreme precaution and safety measures are required.
With the amplifier running, wait the warm-up time. When READY, put OPR switch on and key the amplifier with NO INPUT DRIVE. Read the voltage at TP2. Adjust POT3 (BIAS) to obtain the desired bias current. CAUTION: With a new tube, start at a low plate current. Rotate POT3 for minimum current before keying the amplifier. With the adjustment in the wrong position, the plate current could reach very high values. During this adjustment there is no output power.
threshold (higher sensitivity) can be used. A low threshold can make the EBS activate erratically, for example due to the ambient noise of in the room, or even due to the noise generated by the fan. This is not a problem in itself, except that the tube will dissipate extra power during the times when you hold the key down but do not speak (eg between the words, while speaking). However, these moment are usually brief and it won’t make much difference.
SWR BIAS SCREEN VOLTAGE EBS SENSITIVITY SCREEN CURRENT LIMIT EBS OFF EBS ON Ip PROTECTION Figure 6 39
PLATE CURRENT PROTECTION EBS OFF EBS ON SCREEN CURRENT LIMIT EBS SENSITIVITY SWR1 SWR4 SCREEN VOLTAGE PRE-BIAS SWR BIAS (Ip0) Figure 7 17.2 DISPLAY BOARD ADJUSTMENTS The display board is pre-adjusted during testing. However, when installed in the amplifier, most adjustments need to be fine-tuned. Remove the front panel glass to gain access to adjustments. 17.2.
17.2.4 FORWARD POWER (Adjustment: VR1, marked: RF F) On 20m, operate the amplifier at the full nominal power, as indicated by an external power meter: 750W for DX-1 1500W for DX-2 2000W for DX-2SP 3000W for DX-3 Adjust potentiometer “RF F” for correct display indication 17.2.5 SCREEN CURRENT (Adjustment: VR6, marked IG2+, VR5, marked IG2-) ig2-: put VR5 in the middle position ig2+: connect a mA meter in series with the screen supply, between the control board pin EG2 and the blue screen wire.
17.3 RF SENSOR ADJUSTMENT The amplifier is switched off for this adjustment. Check if adjustment is required as per following procedure, before opening the sensor. Unsolder and remove the metal cover. Connect a transceiver to the input and a dummy load to the output of the amplifier. Connect a voltmeter to pin SW1 or SW2 on the control board (with yellow/black wires). Apply 30-50W RF on 20m (14.2MHz) and read the voltage. Move the voltmeter on pin SW3 or SW4 (red/black wires) and read the voltage.
