OM3500A - OM Power
Contents
1. By scrolling UP DWN select desired Baud Rate which must be the same as baud rate used by your transceiver please refer to your transceiver user manual To confirm your selection press SET When using Yaesu TCVR you need to configure the STOP BIT parameter correctly and confirm selection with SET The communication settings menu can be left by pressing the AUTO button The amplifier will enter AUTO mode only if all settings are correct and connection has been established with your transceiver You can verify that the correct frequency and transceiver type is shown on the LCD display 5 2 2 Connection with not supported TCVRs For communication with TCVRs that are not supported by OM3500A for example JST 245 and older types of Kenwood an external IF 232 converter is to be used You can also use devices from several companies that produce compatible Cl V output which deliver frequency information in ICOM format through the CI V output Then the PA will be connected in the following configuration JST 245 lt gt DB37 JST 245 cable lt gt or other device which has a CI V output lt gt PC OM3500A is connected to the CI V output of the CI V device MicroHam for example Confirm CHOOSE TCVR by pressing SET again and scroll UP DWN to your transceiver type Confirm the selection by pressing SET SET TUNE AUTO MAN TCVR is connected via of MKII Transceiver frequency is visible on the SET TUN2. Instruction Manual NN X 80 ar AJ 0 lt s lt 5 LOAD 90 100 OM3500A SHORTWAVE POWER AMPLIFIER OM POWER s r o 93030 B c 126 SLOVAKIA Email om power om power com TABLE OF CONTENTS OA QI 3 1 Cae 3 3 4 1 4 2 4 3 4 4 4 5 4 6 9 T Deke 5 2 1 5 2 2 3 2 3 5 2 4 5 2 5 5 2 6 3 2 2 2 8 5 2 9 2 35 6 1 6 2 6 3 6 4 GENERAL INFORMATION Introduction Specification Parameters Protection Circuits Indicators SAFETY INSTRUCTIONS GENERAL DESCRIPTION HF Part Power Supply Safety Devices INSTALLATION Grounding Coaxial Cable I O Box and Interface Mains Supply Cooling Remote Control OPERATION Operation Elements Configuration of Power Amplifier TCVR Support Settings Connection with not supported TCVRs Communication Loss Antenna Switching Menu Bandpass Filter Settings Loading Factory Default Settings Mute Option LCD Settings Menu Operation in Manual Mode Tuning of Power Amplifier MAINTENANCE Indication of Fault Conditions Fuse Replacement Tube Replacement Cleaning KR KR On 10 13 13 13 13 14 16 17 18 19 19 20 20 21 22 22 22 26 26 27 27 27 T 7 45 7 3 7 4 7 9 7 6 7 7 7 8 7 9 APPENDIX Example of connection with ICOM Example of connection with ELECRAFT Example of connection wit
3. operating condition ANT 1 which ANT is in use ANT 2 which ANT is in use ANT ANT selection Buttons UP DWN listing in menu MAN manual operating AUTO automatic operating TUNE tuning SET confirms selected parameter OSD Indicator LCD Display 2 x 16 characters 2 SAFETY INSTRUCTIONS WARNING DANGEROUS HIGH VOLTAGE INSIDE The power amplifier is using high voltage up to 3200V DC which is very dangerous for human life Read next safety instructions carefully first before you will start to install and operate power amplifier NEVER VIOLATE NEXT RULES WARNING NEVER ALLOW CHILDREN to play around or to touch power amplifier or connected cables in working condition or to push anything into the case holes WARNING The amplifier contains high voltage circuits Never turn the amplifier on without the upper lid in place DO NOT ATTEMPT TO SHORT OR BYPASS safety switch under upper lid WARNING The OM3500A amplifier can be operated ONLY if both of supply cables are connected The amplifier reaches optimal parameters in 2 phase s system if you do not have 2 phases connect both mains cords into the same phase WARNING The OM3500A amplifier is neither to be used in a WET or HUMID environment nor to be exposed to RAINFALL WARNING Do not turn the amplifier ON without having connected the ANTENNA or properly rated DUMMY LOAD A hazardous HF voltage may build up on the antenna connector after turning
4. Correct baud rate is important DB9 serial port RS232 for KENWOOD YAESU and ELECRAFT TCVRs Correct baud rate and type is required for successful operation If both CI V and TCVR cables are connected then CI V disables RS232 Otherwise selection of interface is done via TCVR type DB 9 RS232 port is used for communication with your PC Please use setting you would normally use if using direct TCVR PC connection RCA Phono Automatic Level Control is used when tuning the PA to block drive level CAUTION We only recommend using ALC feature while operating RTTY FM and other 100 duty modes CONTROL The CONTROL socket is a single DB 15 connector that provides many connections to the amplifier from your transceiver Use shielded cable for all connections to this connector You will need to fabricate a cable with the proper connector for your transceiver or use individual connectors as described below 11 ANT amp BPF SW PIN OUT ALC Out NC INHIBIT Control voltage TX INHIBIT for Yaesu and Elecraft this supersedes ALC output DB 25 is used for switching of external HP BPF or external Antenna Switch Maximum switching of 30V 0 5 is possible PIN OUT CON DUR WN antenna port 1 antenna port 2 antenna port 3 antenna port 4 antenna port 5 antenna port 6 antenna port 7 antenna port 8 antenna port 9 antenna port 10 COMMON port of ANT SW NC GND BPF 160m BPF 80m BPF 40m BP
5. 60 4 6 Remote Control Control of the amplifier is possible remotely by using REMOTE BOX optional Connection is done by REMOTE socket maximum cable length should be 10 meters 9 OPERATION WARNING Before switching PA on make sure that amplifier is grounded antenna or dummy load is connected and line cord is putted to the outlet CAUTION Before switching PA on check all connections between PA and TCVR CAUTION Do not turn on for at least 2 hours after unpacking it and locating in its operating location Especially when amplifier is moved from a cold place to a warm one because not visible condensation may develop and this could result in damage to the high voltage circuits of the PA CAUTION Never try to change antenna output during a transmission to avoid warranty loss NOTE When you decide to have a short operating break place the amplifier in the standby mode rather than switch it off 5 1 Operation Elements There is couple of operational elements accessible or visible on the front panel 2 A 14 TUNE LOAD OFF ON OPR STBY RF OUTPUT REFLECTED POWER 02 Anode capacitor for tuning tuning of higher frequencies to 0 lower frequencies to 100 Output capacitor tunes antenna load resistance to amplifier Capacity is low at 100 and high at 0 on the scale You switch off the amplifier by pressing this button You switc
6. The amplifier will be turned to STBY mode After approx 2 sec the control circuits will switch the amplifier back to OPR CAUTION If the fault will repeat 3 times after each other the control circuits will turn the amplifier to STBY mode Bringing the amplifier back to OPR mode is enabled by using the OPR STBY switch only After reaction of safety circuits the FAULT LED will be lit up for approx 5 sec depending on the nature of the fault Flashing LED signalizes IP anode currency exceeded HV low anode voltage FAULT reflected output exceeded GRID MAX first currency exceeded screen grid currency exceeded GRID MAX HV maximum load power exceeded GRID MAX IP zero output power during tuning HV IP tuning fault incorrect tuning of the Pi L output circuit 26 In case your OM3500A amplifier is not working correctly please contact the manufacturer or your dealer Manufacturer s contacts OM POWER s r o 930 30 B c 126 SLOVAKIA Email om power om power com 6 2 Fuse Replacemeent The user is allowed to change mains fuses 6 3 x 32mm accesible from the rear panel only In the case of interrupted fuse fuses inside the power amplifier contact your dealer please 6 3 Tube Replacement In the case of vacuum tube damaging contact the manufacturer or your dealer for ordering new one You will get instructuions how to change tube and how to preset proper parameters too Be very careful you will
7. tuned in such a way that the current is between 20 mA to 50 mA At currents beyond these values the operating point will be shifted and IM products will be rapidly increased If a value of 70mA is exceeded the safety devices will switch the amplifier to STBY mode 5 3 1 AUTO or MANUAL There are two possibilities of operation mode in OM3500A AUTO or MANUAL Normally when you are using CAT interface connection between TCVR and PA in AUTO mode PA will tune automatically to the TCVR frequency If you do not have or use CAT connection you will use MANUAL mode You must manually select proper band and segment corresponding to TCVR s band and frequency Then OM3500A will tune automatically to this manually selected band segment 5 3 2 Manual tuning instructions OM2500A has been design to deliver maximum output power at 50 Ohms load Parameters for PA auto tuning using real 50 Ohm loads are stored in the memory factory default To deliver maximum output power to a real load you need to adjust the tuning according to your real antenna impedance This has to be done manually in TUNE mode see 5 3 3 for details First off all PA must be switched on 1 Set the multimeter switch to the HV position 2 Set the OPR STBY switch to the STBY position 3 Pressthe ON button 23 The amplifier is prepared for operation with the following automatic steps Toroidal transformers are switched on step by step The cooling blower for the final
8. you will be able to work for long time with this amplifier 5 3 3 Tuning Adjustment Entering the TUNE mode is done by pressing the TUNE button The OM3500A then switches the transceiver to RTTY and sets the frequency to corresponding segment By changing the values of TUNE and LOAD capacitors we tune the PA as per manual tuning instructions see 5 3 2 The optimally tuned amplifier will deliver full output without approaching the maximum Screen Current of 50mA After tuning the amplifier save the settings by pressing SET and PA will automatically tune frequency of your transceiver to next band segment Follow the same procedure for all bands and segments if needed By pressing MAN or AUTO buttons PA and TCVR will return to standard operating mode SE TUNE AUTO MAN LJ Dividing of bands into segments Width of the segments kHz 15 gt 07 70 25 6 MAINTENANCE 6 1 Indication of fault conditions OM3500A has the following indication LED on the front panel GRID MIN indication of first gird current GRID MAX max First grid current exceeded HV measuring of anode voltage by bar graph IP measuring of anode currency by bar graph FAULT fault OPR amplifier in operation mode STBY amplifier in standby mode WAIT heating of tube after switching on the amplifier NOTE Should a fault condition appear during the tuning or operation of the amplifier the safety circuits of OM3500A will react
9. E AUTO MAN display a 5 2 3 Communication loss If TCVR is not connected or communication settings are incorrect the message COMMUNICATION LOST will be displayed You can still use PA by entering MANUAL mode MAN Button or by correcting the transceiver connection problem Example of Communication loss message SET TUNE AUTO MAN 5 2 4 Antenna Switching Menu If you have 3 party external antenna switch connected to your amplifier i e MicroHAM TEN SWITCH you need to configure the assignment of each port to a specific band or antenna By pressing SET and scrolling to ANTENNA SETTINGS and confirming by SET you get current band and its antenna selection By scrolling UP DWN you can select BAND which you want to assign to current ANTENNA selected Then select how many antennas you want per current band 1 or 2 and always confirm your selection by pressing SET AUTO MAN By scrolling UP DWN you assign which PORT is used on your external antennas switch for this particular antenna ANT 1 ON PORT 01 TUNE AUTO MAN DWN UP Shall you decide to use 2 antennas for this band then after confirming that with SET configuration continue to the other antenna selection port selection To finish Antenna switch configuration you can either press AUTO or MAN 5 2 5 Bandpass filter switching Switching of external band pass filters is automatic and needs to follow pin out of BPF connector For m
10. F 30m BPF 20m BPF 17m BPF 15m BPF 12m BPF 10m COMMON BPF port NC GND 4 4 Mains Supply WARNING The power Amplifier OM3500 HF has to be connected TO THE MAINS WITH BOTH CABLES The amplifier reaches optimal parameters in the system with 2 phases Every phase has to be able to deliver 2 5kVA If you do not have 2 phases system connect both mains cords into the same phase In such a case the amplifier can t deliver full power output CAUTION Be sure you got PA with properly terminated line cable corresponding with your power system s outlet If not contact your dealer In such a case you should make the necessary changes using a licensed electrician CAUTION Be sure that your power system is correctly wired and properly rated To use adequately sized and connected grounding system is also very important 4 5 Cooling CAUTION The amplifier must be installed in such a way that free flow of hot air from the tube is allowed Do not obstruct air intake and exhaust areas of the PA The centrifugal blowers provide the necessary cooling of the amplifier even during long contests The main blower is activated by switching the PA on and it is turned off when cooling is finished approx 1 5 min after switching off the PA depending on the temperature of the tube The supplemental fan is turned on depending on the temperature of the air exiting from the amplifier It is switched on at 70 C and switched off at
11. Safety Devices Control and monitoring circuits ensure control and safety during malfunctions of the PA These are on the Control board which is located on the chassis subpanel 4 INSTALLATION NOTE Read this chapter carefully prior you will start installation Before unpacking inspect shipping woody container first if it is not damaged Keep all of packing parts for possible future shipment Check unpacked power amplifier If you find some damaging contact your dealer immediately to keep full warranty During installation go step by step according to next parts 4 1 Grounding CAUTION The amplifier has to be grounded properly Connect the screw on the rear panel of the amplifier to your local grounding system with a copper cable use a cross section of 4 mm at least Connect your transceiver to the same grounding system of your shack carefully Use minimum length cables and make certain that the connections are both physically and electrically sound With poor grounding you may risk damaging your equipment having problems with or your transmitted signal may be distorted 4 2 Coaxial Cable The output of the transceiver is to be connected to the input of the amplifier via RG58 or similar cable For the connection between the power amplifier and the antenna RG213 or similar coaxial cable suited for high power is recommended Both the INPUT and OUTPUT SO 239 sockets with Teflon insulation is used Rear view of
12. WARC 3500W in SSB and CW 3000W in RTTY AM and FM Usually 60 to 80W for full Output Power 50 Ohm VSWR lt 1 2 1 17 dB 50 Ohm unbalanced 2 1 Automatic switching to STBY when reflected power is 350W or higher 32dB below nominal output 50 dBc Manual or AUTO Less than 0 5 sec within the same band Less than 3 sec if out of the band GU78b Ceramic tetrode Centrifugal blower Axial blower 2 x 230V 50 Hz one or two phases 2 pcs of toroidal transformer 2 5 kVA 485 x 200 x 455mm width x height x depth 43 kg 1 2 2 Protection Circuits There are 8 special protection circuits used in the amplifier They are activated when one or more of next parameters exceed defined values or some unwanted occasion occurs e VSWR too high e Anode current too high e Screen current too high e Grid current too high e Mistuning of PA e Hot switching protection e Soft start for protecting your fuses e switch on blocking at opened amplifier 1 2 3 Indicators There are couples of LED and bar graph indicators visible on the front panel to inform you about value of some parameters or operation status Bar graph indicators Power output 50 LED Reflected power 20 LED 192 current 10 LED Anode voltage anode current tuning 30 LED LED Indicators Current at control erid Ig1 2 LED WAIT preheating of tube 150 sec STBY standby OPR operation mode FAULT failure switching off for abt 2 sec INHIBIT
13. do it only on your own risk If you are not comfortable to replace vacuum tube itself contact your Service Center please 6 4 Cleaning To prevent damage of amplifier surfaces and plastic components do not use aggressive chemicals for cleaning Do not open the amplifier for cleaning Outer surface may be safely accomplished by using piece of soft cotton cloth moistured with clean water or window cleaner 27 APPENDIX f Example of connection for Icom 399 9 INY 109105 d VOOStINO 1ndino 1 93 006000 wo LLNV ZLNV 28 Example of connection for ELECRAFT 7 2 222 58 Woo LISIHNI 3989 INY TONLNOD JW MIIA VOOSENO Andino INV 9 00000 yeJl 9 3 XYL 29 Example of connection with Yeasu 7 3 900550 9 I NY OHINOO INV 93 viva dINOOOLLA 30 Example of connection with antenna switch and BPF 7 4 8 LNY OHINOO MIIA VOOStINO yms INV VLVO Ld 31 Example of connection USB micro II with 1C7800 or 1C7700 7 5 uod asn NIO 310N3H 26258 eRe ORC dll 3989 INY JOHINOO DTV YADL AID LNO NI 3LOWSY A39 008221 002221 031 VOOS INO INV 9 32 Example of c
14. ely 2 seconds Meanwhile reduce the input power 10 11 12 13 Set TUNE knob in such a way that the TUNE LED lights up maximum left multimeter in TUNE position Set LOAD knob in such a way that the TUNE LED on the TUNE scale lights up under the sign If it is possible to obtain the LOAD in 2 positions set the position that is further to the right Repeat tuning several times according to 8 and 9 output power should be abt 500W Increase the input power to about 60W until an output power of approximately 3500W will be reached Repeat steps 8 and 9 Set TUNE knob to maximum output power RF POWER LED lights up max right 24 After this procedure the amplifier is tuned correctly and ready to give 3500W output power in all operation modes At optimal tuning and full output power a positive max 50 current goes through the second grid On 24 and 28 MHz bands optimal tuning can be achieved when one or two LEDs are lit up to the left from the position V If less output is desired you can simply decrease the load of the transceiver CAUTION Should the amplifier demonstrate any malfunctions during tuning or should it not behave in accordance witch the description interrupt the tuning procedure immediately and check the amplifier Be sure to have not done any mistakes in choosing bands or TUNE LOAD values Be sure that VSWR is not higher than 2 1 and input power is LOW After excluding possible human mistakes
15. h YEASU Example of connection with Antenna Switch and BPF of connection USB Micro KEYER with IC7800 or 1C7700 Example of connection USB Micro KEYER II with another ICOM Example of connection USB Micro KEYER with YAESU or ELECRAFT Example of connection PA with MicroHAM MK2R etc CI V output Block Diagram of OM3500A power Amplifier 28 28 29 30 31 32 33 34 35 36 1 GENERAL INFORMATION 1 1 Introduction all short wave amateur bands from 1 8 to 29 7 MHz including WARC bands and all modes he OM Power model OM2500A is a fully automatic power amplifier designed for use on It is equipped with one GU78b ceramic tetrode THE ADVANTAGES OF OM3500A Full compatibility with ICOM ELECRAFT KENWOOD TEN TEC ORION YAESU and Icom transceive protocol using by MicroHAM devices CI V output Automatic switching between bands Automatic tuning within the band according to segments Automatic switching of band pass filter Automatic switching of antenna switches The possibility to use 2 different antennas within one band or segment 1 2 Specification 1 2 1 Parameters Frequency Coverage Power Output Input Power Input Impedance Power Gain Output Impedance Maximum Output SWR SWR protection Intermodulation distortion Suppression of harmonics Tuning Response speed of Auto Tube Cooler Power supply Transformers Dimensions Weight Amateur Bands 1 8 29 7 MHz including
16. h on the amplifier by pressing this button After 3 min of warm up delay amplifier will be ready for operation OPERATE sets the amplifier ready for transmit operation In STBY if WAIT LED is on or the amplifier is OFF the amplifier is in bypass mode and your transceiver is directly connected to the antenna Maximum allowed power in bypass mode is 400W Bar graph shows output power Bar graph shows reflected power from the antenna Maximum level is 350W otherwise amplifier switches to STANDBY mode Bar graph measures the current of the second grid from 20mA to 80mA Bar graph measure the anode voltage anode currency or tuning of the amplifier INHIBIT ANT 1 Pd ANT 2 SET AUTO INHIBIT ANT ANT1 ANT2 SET TUNE AUTO DWN UP Indicates interruption of transmission during the tuning process of the PA If indicated by RED LED then PA is in STBY mode during a retune operations within the same BAND then the PA will retune according to the frequency of the transceiver When changing the BAND INHIBIT will stay lit until the KEY IN is released and the tuning process will start After that PA is automatically ready for operation The amplifier is capable of automatic antenna switching ie 80m CW and 80m SSB can be split between two antennas The amplifier will automatically select desired antenna by selecting last used antenna on a given frequency button f
17. llent linearity by the voltage stabilization of the control grid bias and the screen voltage The power input is given to the control grid using a broadband input circuit with an input impedance of 50 Ohms This adaptable input circuitry ensures a good input SWR better than 1 2 1 on all amateur bands this amplifier a tetrode GU 78b is used in grounded cathode circuit input into control The output of the amplifier is a Pi L circuit The ceramic capacitor for TUNE and LOAD are divided This enables the amplifier to be tuned exactly and makes it possible to easily return to the previously set positions after band changes Top view on the opened OM3500A Tetrode GU78b PWR Meter Blower ee SaaS ae ME M Switch ON Board ped em fi L En i Output Pi L Circuit Tuning Capacitor Subpanel Power Supply Board 3 2 Power Supply ower supply of the amplifier is comprised of two of 2 5 kVA toroidal transformers A soft D is provided using relays and resistors The high anode voltage is made by combining 8 x 420 V total 3360V 2A Each has its own rectifier and filter In the high voltage circuit safety resistors are employed to protect the amplifier against overload The source for screen grid is regulated by parallel stabilization with BU941 NPN Darlington transistors and delivers a voltage of 350V at 100mA The 120V for the control grid is regulated with Zener diodes 3 3
18. onnection USB micro with another Icom 7 6 3A3 0942 u NIO YADL AID LNO NI AJA nod gsn Ed 9 INY TONLNOD JW wos MIIA VOOSEtINO LNdLNO INV 9 33 Example for connection USB micro KEYER with Yeasu ELECRAFT 7 7 yod gsn VOOStINO 4 3989 PLINY lOHINOO LAdLNO INV 9 viva 1 NSAVA 34 Example of connection PA with MicroHAM MK2R etc with CI V output 7 8 asn ZEZ 4 HJAZ2094121ul 1indinO YADL MIO 100 NI 3103 11 399 I NY lOHINOO DIV l4voala nsavA VOOS INO Andino LNV 9 35 Block Diagram of the OM2500A Power Amplifier 7 9 VOOSE NO MS 349 LNY Ly O 1997135 GNVS JOHINOO Od AV 1dSIG G01 HAOL LNO A3 NI MS 815 MS 10M1NO2 Josues MS 13409 T 3 osnj L need 941 380d a OANT ZOQO NT Z MS qT MS SI YILIN 1 l 36
19. or MENU Confirmation of selection Saving of selected value Saving of tuning parameters Push button for selection of TUNE mode Push button for selection of AUTOmatic mode Push button for selection of MANUAL mode Push button for selection of band segment or parameter 5 2 Configuration of Power Amplifier During the warm up period the STBY and WAIT LEDs will be illuminated If a transceiver We the ON button is pressed the amplifier will start to heat the final amplifier tube is connected to the correct port and all communication settings are right the operating frequency AUTO and the type of transceiver will be indicated on the alphanumeric display After successful heating of the TUBE you can enter operating mode by pressing the OPR button Example of Automatic mode with ICOM TCVR Type of supported TCVR and working SET TUNE AUTO MAN DWN Ul frequency is visible on the display AUTO LED is ON 5 2 1 TCVR Support Settings Supported transceivers ICOM ELECRAFT KENWOOD TEN TEC ORION YAESU TUNE AUTO MAN Press SET button and scroll UP DWN to CHOOSE TCVR Confirm CHOOSE TCVR by pressing SET again and scroll UP DWN to your transceiver type Confirm the selection by pressing SET SEI TUNE AUTO MAN Continue by selecting Baud Rate Press SET button and scroll using UP DWN to BAUD RATE Press SET again SET TUNE AUTO MAN Baud rate for TCVR PA communication is shown on the display
20. ore details see Example of connection with antenna switch and BPF in the Appendix 5 2 6 Loading factory default settings In the rare case of needing to restore factory default settings press SET and scroll using UP DWN to LOAD DEF VALUES and confirm by SET In the rare case of needing to restore factory default settings press SET and scroll using UP DWN to LOAD DEF VALUES and confirm by SET SET TUNE AUTO MAN Ld 20 LOAD DEF DALJET LO AES RUSH SET SET TUNE AUTO MAN TO ALL PUSH TU PUSH SET SET TUNE AUTO MAN 5 2 7 MUTE option Then select if you want to erase all settings pressing TUNE or just one setting value SET button In the case of resetting a single parameter use UP DWN to select which option and confirm by SET When operating the OM3500A with an Icom transceiver without TX INHIBIT for disabling TX we recommend blocking of the TX while tuning using ALC control mainly while operating FM RTTY AM The ALC Input of your transceiver should be connected to the ALC Out of OM3500A SETTINGS MUTE AUTO MAN BAHD 5 5 MHz LEW OF MUTE 288 SET TUNE AUTO MAN Using SET and scrolling UP DWN select SET MUTE and confirm it by SET Then configure MUTE LEVEL for each band so it results in no power being transmitted by TX when performing TUNE procedure 21 5 2 8 LCD Settings Menu Using SET and scrolling UP DWN selec
21. t SET LCD CONTRAST and confirm it by SET SET TUNE AUTO MAN By pressing Up or DWN you can vary contrast of the LCD display Finally press SET to confirm selected value 5 2 9 Operation in MANUAL mode To enter Manual mode of the PA press MAN By pressing MAN repeatedly you select BAND and band segment You can control the segment or band by scrolling the UP DWN buttons AUTO MAN LI 5 3 Tuning of Power Amplifier The OM3500A amplifier is operated in class AB Thus it s possible to obtain a maximum output power at excellent linearity For this purpose the amplifier has to be tuned carefully 22 WARNING Before starting tuning you have to check if the right antenna or a 50 Ohms load resistance is connected at the antenna output CAUTION The operation of a mistuned PA will cause malfunctions the increase of grid current the GRID MAX LED will light up and problems with TVI BCI CAUTION The grid current is shown with 2 LED diodes It s normal if the green LED is flashing or may be shining a little bit during peak operation If you overload the amplifier the output power increases the grid current at very small rates and the red GRID MAX LED is shining and the safety devices switch the PA to STBY You must decrease the input power CAUTION In SSB mode you will have good output power if the green LED lights up a bit The current of screen grid is measured and shown in a Bar graph Indicator The amplifier has to be
22. the amplifier OM3500A AC Sockets Fuses OUTPUT REMOTE I O Interface INPUT 4 3 1 0 Box and Interface Control of Amplifier and communication with TCVR as well as Antennas BPF switching can be done via the rear panel O Interface Control cable maintains TX RX switching of the PA TX GND The cable is shielded On the side of the power amplifier a CINCH socket is used On the side of your transceiver you have to use a socket suitable for this transceiver During transmitting the middle pin is connected to the ground The relays of the OM3500A have to be switched earlier than HF is applied cold switching Modern transceivers they have a time delay between PTT switching and power output CAUTION If you are using and older transceiver or transmitters without time delay we recommend to connect the in such a way that the transmit receive switch foot switch for example is connected with the KEY IN socket of the amplifier The KEY OUT socket is to be connected with the PTT socket at the transceiver The amplifier is equipped with two safety devices which ensure that the output relay is not switched under power mistakenly hot switching 10 KEY IN KEY OUT CI V TCVR PC ALC RCA Phono Input signal PTT switching voltage current 5V 2 mA RCA Phono Output signal PTT maximum switching of 30V 50 Mono 3 5mm Jack for connection of ICOM TCVRs or devices that provide compatible protocol
23. the amplifier on with no antenna or dummy load connected WARNING Before opening the upper lid of the amplifier make sure that power supply has been disconnected AT LEAST 5 minutes allowing the electrolytic capacitors to discharge fully Disconnect power cord from the outlet CAUTION The amplifier must be installed in such a way that free flow of hot air from the tube is allowed The amplifier must not be installed in a constrained surrounding i e tight shelves etc During long time operation ventilation grid can reach high temperature Do not touch the top cover of the in these places during operation CAUTION The amplifier must be properly grounded during operation x CAUTION During operation the amplifier must be installed in such a way that the rear side remains accessible CAUTION The amplifier is an A category product In a household it can influence other electric appliances In such cases the user is to take proper actions to mitigate this disturbance CAUTION Make sure that all screws holding the case together are properly in place and tightened before carrying the amplifier with the handles CAUTION Read this manual carefully Fallow all of instructions during installation and operation to avoid damage to the amplifier not covered by manufacturer s warranty Do not attempt to perform any change of hardware or software 3 GENERAL DESCRIPTION 3 1 HF part grid This amplifier achieves exce
24. tube is switched on The multi meter bar graph measures the high voltage the normal value is 3 4 KV The WAIT LED lights up CAUTION After switching on please confirm that the blower is operating properly Air must be flowing from the ventilating aperture above the tube If there is any concern or no air flow press the OFF button immediately Heating of the tube takes about 150 seconds After this time the WAIT LED goes out and the amplifier is ready for operation Enter TUNE mode Depending on the input power level and antenna parameters two situations can occur First when your antenna parameters are close to real 50 Ohms and input power not exceeds allowed maximum PA stay in OPR mode and you will see the output power You have to do just little adjustment steps 8 9 12 13 to get maximum output power Second if your antenna parameters are not very good and input power is higher than 15watts safety devices will switch PA automatically to STBY In such a case start with step 4 go thru all next steps E A IA A Reduce the power output of your transceiver to the minimum Switch OPR STBY to OPR position OPR LED lights up Choose the TUNE position of multimeter Transmit and increase driver power to cca 10W CAUTION If the input power is higher than 15W and the power amplifier is not correctly tuned the safety devices will switch to STBY The amplifier will automatically reset and switch back to OPR mode after approximat
Download Pdf Manuals
Related Search