OM POWER OM2501A User manual

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MADE IN SLOVAKIA
WWW.OM-POWER.COM
OM Power, s.r.o. 93030 Báč126,
SLOVAKI A
Co n t a ct : + 4 2 1 905 321 410
e-mail : [e-mail]
e-mail : om-power@om-
power.com
OM2501A
( OM3501A)
SHORTWAVE
POWER AMPLIFIER

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TABLE OF CONTENTS
1. GENERAL INFORMATION .................................................................... 4
1.1. Introduction ………………………………………………………. 4
1.2. Specification ………………………………………………………. 4
1.2.1. Parameters ………………………………………………. 4
1.2.2. Protection Circuits ………………………………………………. 5
1.2.3. Features ………………………………………………………. 5
1.2.4. The Advantages of OM2501A …………………………………… 5
2. SAFETY INSTRUCTIONS ………………………………………………. 6
3. GENERAL DESCRIPTION ………………………………………………. 7
3.1. HF Compartment …………………………………………………………. 7
3.2. Power Supply …………………………………………………………. 9
3.3. Safety Devices …………………………………………………………. 9
4. INSTALLATION ………………………………………………………. 9
4.1. Grounding ……………….………………………………. 10
4.2. Coaxial Cable ………………………………………………. 10
4.3. Control Cable ………………………………………………. 11
4.4. Cooling ………………………………………………. 11
5. OPERATION ………………………………………………………. 12
5.1. OM2501A Front Panel ……………………………………………. 12
5.2. OM2501A Control ………………………………………………… 13
5.3. Preparing for operation ………………………………………… 20
5.4. Operation mode ……………………………………………………. 26
6. MAINTENANCE ……………………………………………. 30
6.1. Indication of Fault Conditions ………………………………… 30
6.2. Fuse Replacement ……………………………………………. 31
6.3. Tube Replacement ……………………………………………. 32
6.4. Cleaning ………………………………………………. 32

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7. APPENDIX ………………………………………………………. 32
7.1. Primary AC selection ……………………………………………. 32
7.2. Controlling OM2501A with FLEX Radio Series 6xxx ……………. 34
7.3. OM2501A Remote Control ………………………………..………. 36
7.4. Remote Control using own public IP Address ............................. 40
7.4.1. Changing OM2501A+ connection settings ................................. 40
7.4.2. Setting up in the Remote software ............................................... 41
7.4.3. Remote Control without own IP Address, behind a router .......... 42
7.5. OM2501A firmware upgrade …………………………..………… 43
7.6. Icom connection with OM2501A ……………………………….… 47
7.7. Yaesu plus BPF plus ANT Switch connection with OM2501A … 48
7.8. Control panel connectors pin-out …………………………….…… 49
7.9. Block Diagram of the OM2501A Power Amplifier …………..… 53
7.10. Troubleshooting ………………………………………………………. 54

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GENERAL INFORMATION
1.1. Introduction
he OM Power model OM2501A and OM3501A are designed for all short wave amateur bands
from 1.8 to 29.7 MHz (including WARC bands) and all modes. OM2501A is equipped with a FU-
728F or GU84B ceramic tetrode and OM3501A is with GU78b ceramic tetrode.
1.2. Specification
1.2.1. Parameters
Frequency Coverage Amateur Bands 1.8 – 29.7 MHz including WARC
Power Output OM2501A 2500+ W in SSB/CW on HF bands
2000 W in RTTY and DIGI modes
Power Output OM3501A 3500+ W in SSB/CW on HF bands
3000 W in RTTY and DIGI modes
Input Power Usually 40 to 60W for full Output Power
Input Impedance 50 Ohm, VSWR < 1.5 : 1
Power Gain 17 dB
Output Impedance 50 Ohm unbalanced
Maximum Output SWR 3 : 1
SWR protection Automatic switching to STBY, when reflected power
is 350W or higher
Intermodulation distortion -32dB below nominal output
Suppression of harmonics < -50 dBc
Tubes FU-728F or GU84B in OM2501A
GU78b in OM3501A
Cooler Centrifugal blower + Axial blower
Power supply switchable 2 x 220 ,230V, 240 V – 50 Hz one or two phases
Transformers 2 pcs of toroidal transformer 2 kVA ( 3 kVA for OM3501A)
Dimensions 485 x 200 x 455mm (width x height x depth)
Weight 42 kg ( OM3501A 45kg )
T

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1.2.2. Protection Circuits
There are several protection circuits used in the amplifier. They are activated when one or
more parameters exceed defined values or some unwanted condition occurs.
•VSWR too high
•Anode current too high
•Anode voltage error
•Screen current too high
•Screen voltage error
•Grid current too high
•Grid voltage error
•Heating voltage error
•Mistuning of PA
•Temperature too high
•Soft start for fuse protection
•“switch-on blocking “ at opened amplifier
1.2.3. Features
The manufacturer implemented some of the company’s newest development results with most
wanted operating and safety features into this new model:
•High level of protection
•Memory for faults and warnings, easy maintenance
•Automatic set-up anode current (BIAS) – no need to adjust manually after changing
the tube
•Three programmable working modes of the centrifugal blower ( turbine ) + axial blower
•Full QSK
•Many operational parameters to display
•Easy transport due to detachable HV transformer
1.2.4. The Advantages of OM2501A
•Full compatibility with: ICOM, ELECRAFT, KENWOOD, TEN-TEC ORION, YAESU, Icom
transceive protocol using by MicroHAM devices ( CI-V output ), FLEX Radios and Anan.
•RF sensitive Band and Frequency switching, for use with radios which do not have
CAT. We recommend using CAT and BAND DATA information due to the much
faster band changing whenever possible.
•Automatic switching between bands. Automatic tuning within the band according to segments.
•Automatic switching of Band Pass Filter – BAND DATA output compatible with YAESU radios
BCD code.
•Automatic switching of Antenna switches. The maximum number of antennas is 10, controlled
by BCD output code.
•Remote control via available PC Application. http://www.om-power.com/downloads

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2. SAFETY INSTRUCTIONS
DANGEROUS HIGH VOLTAGE INSIDE!
The power amplifier is using high voltage up to 3400V 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 THE FOLLOWING SAFETY RULES!
NEVER ALLOW CHILDREN to play around PA or to touch power amplifier or connected cables
in working condition, or to push anything into the case holes!
Never turn the amplifier on without the upper lid in place. DO NOT ATTEMPT TO SHORT OR
BYPASS safety switch under upper lid!
The OM2501A amplifier should not be used in a WET or HUMID environment or be exposed to
RAINFALL!
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
the amplifier on with no antenna or dummy load connected!
Before removing the upper lid of the amplifier make sure that power supply has been
disconnected AT LEAST 10 minutes allowing for the electrolytic capacitors to discharge fully.
Disconnect power cord from the outlet!
Any work inside the PA (internal fuses replacement, tube replacement, etc.) should be carried
out only by aprofessionally qualified person!

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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 extended operation the tube ventilation grid can reach high temperature. Do not touch
it!
The amplifier must be properly grounded during operation.
During operation the amplifier must be installed in such a way that the rear side remains
accessible.
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.
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 Compartment
his amplifier is using ceramic tetrode in a grounded-cathode circuit (input into control grids).
The OM2501A (OM3501A) amplifier achieves excellent linearity by the voltage stabilization of
the control grid bias and the screen voltage. The power input is fed to the control grids, using a
broadband input circuit with an input impedance of 50 Ohms. This adaptable input circuitry
ensures a good input SWR (better than 1,5 : 1) on all amateur bands.
T

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The output of the amplifier is a Pi-L circuit. The variable capacitors for TUNE and LOAD are separate.
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 OM2501A
Tetrode FU728F Blower Switch-ON Board
Output Pi-L Circuit Tuning Capacitor Front Subpanel Power Supply Board

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3.2. Power Supply
This Power amplifier uses two 2 kVA toroidal transformer. A soft start is provided using relays and
resistors (placed on the switch-ON board). The high voltage is made by combining 8 x 410 V (total
3280V) @ 2,0 A . Each has its own rectifier and filter. In the high voltage circuit, safety resistors are
employed to protect the amplifier against overload (placed on the power supply board).
The separate screen grid supply is regulated and stabilized with MOSFET circuits and delivers abt.
350V DC at 120mA. Control grid voltage is also stabilized (-120V DC). Change of stabilized first grid
voltage is controlled by the software (EBS for example).
The transformer primary is Tap adjustable for 220 , 230 or 240V AC.
The factory setting is 230 VAC .
If the AC voltage in your network is 220 or 240 Volts, you need to set the correct transformer
tap before first starting the PA. See part 7.1. for more information. Other primary voltage is possible
on request (for example 200V 50/60 Hz for Japan).
3.3. Safety Devices
Control and monitoring circuits ensure control and safety during malfunctions of the PA. These are
placed on the Control board, which is located on the chassis subpanel.
One of the important safety elements is a
mechanical switch for AC blocking an opened
amplifier.
4. INSTALLATION
Read this chapter carefully prior to starting installation. Before unpacking inspect shipping
carton for any damage. Keep all of packing parts for possible future shipment. Check
unpacked power amplifier. If you find any damage, contact your dealer immediately to keep
full warranty.
Type of supported TCVR and working
frequency are visible on the display.
AUTO LED is ON.

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4.1. Grounding
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
mm2 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, have problems with TVI/BCI or possible distortion
of your transmitted signal.
4.2. Coaxial Cable
The output of the transceiver is to be connected to the input of the amplifier via RG58 or similar 50
Ohm cable. For the connection between the power amplifier and the antenna, RG213 or similar
coaxial cable suited for high power is recommended. SO-239 sockets with Teflon insulation are used
for the HF INPUT and OUTPUT connectors.
Rier view of the amplifier OM2501A
Mains PlugsFuses HF Output
Grounding point Blower Control HF Input

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4.3. Control Cable
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 OM2501A have to be switched earlier than HF is applied (cold switching). Modern transceivers
they have a time delay between PTT switching and power output.
If you are using an older transceiver or transmitters without time delay, we recommend
to connect the PA 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. If there is possible to adjust TX delay
in your TCVR, set the delay to 15ms, please.
The amplifier is equipped with safety devices, which ensure that the output relay is not switched
under power mistakenly (hot switching).
KEY IN RCA Phono - Input signal PTT switching voltage / current -5V /2mA)
KEY OUT RCA Phono - Output signal PTT (maximum switching of 30V / 50mA)
See section 7.9. for Control and ANT/BPF connector PIN-OUT.
Be sure that your power system is correctly wired and properly rated! To use an
adequately sized and connected grounding system is also very important!
4.4. Cooling
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 blower provides the necessary cooling of the amplifier, even during long contests. The
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). Blower working mode is
programmable (3 modes). See page 19 for more details.

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5. OPERATION
Before switching PA on, make sure that amplifier is grounded, antenna or dummy
load is connected, and line cord is plugged into the outlet. Be sure you have selected
the proper AC input TAP (Sect 7.1)
Do not turn PA on for at least 2 hours after unpacking and located in its operating
location. Especially when amplifier is moved from a cold place to a warm one as
condensation may develop. This condition could result in damage to the high voltage
circuits.
We do not recommend changing antennas during a transmission. (Hot switching)
When you decide to have a short operating break, We recommend placing the amplifier to
the standby mode rather than switch it off.
5.1. OM2501A Front Panel
Front panel of the OM2501A (OM3501A) is almost empty…Containing only the touch TFT display
plus two control switches.
ON -Main Switch. After turning ON, a small 12V APU for logic, protection circuits and the
display will be activated. High voltage and RF circuits are still OFF.
OPR/STBY -Short press for switching betwen STBY and OPERATION mode.

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ON/OFF -Long press (1 sec.) for switching the PA ON (tube heating first), 2 seconds for PA
OFF. Always use the ON/OFF button as this allows for a predetermined (software controlled) time to
cool down the tube and inside the PA compartment.
5.2. OM2501A control
Turn ON the green Main Power switch and the home screen will lights up. Initial control touch
buttons are visible on the bottom line.
Remember that the home touch screen is active for some information and control settings , while the
PA is still OFF!
BAND
Touch the left side of BAND button to go down, touch the right site to go up. The band information is
displayed above the button.
ANTENNA
Transmitting antenna choice. Functional ONLY when the antenna switch is programmed and
antennas are defined (see page 16). This antenna feature allows switching between antennas
authorized for the current band. An external antenna switch is controlled by BCD code at the
ANT/BPF output (see Section 7.9).
INFO
Information display shows basic information about the PA: serial number, software version, time ON,
tube serial number and nominal Main voltage.

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The information screen also provides an
overview of the last 20 warnings and
faults:
Press FAULTS.
Press EXIT to go back to the home
screen.
Now press SETTINGS. This display
shows various menu settings for CAT,
NO CAT, ANTENNA, DISPLAY, EBS,
CLEAR user settings for one or all
bands, BLOWER mode and other INFO.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.

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Screen shows settings possibilities for
CAT, ANTENNA, DISPLAY, NETWORK
SETTING, EBS, BLOWER and other
INFO.
Scroll to CAT SETTINGS (up or down)
and
press SET.
Scroll to your TCVR family (up or down)
select appropriate bit rate (left or right)
then press SET.
Or select NO CAT and press SET.
We recommend using the CAT
connection whenever possible because, in such a case, the OM2501A (OM3501A) has permanent
information about the transmit frequency and is immediately ready for transmitting.
With a setting of NO CAT the OM2501A (OM3501A) detects transmit frequency from the input signal.
With the input signal frequency changing the PA automatically reacts and tunes itself to optimal
output parameters.. If NO CAT is used, we recommend using BAND DATA (BCD) information for
much faster band changing.
If you choose YAESU or ICOM NEW,
after SET pressing you will go to deeper
level which allows you to select specific
type of TCVR.ee the following picture for
ICOM NEW selection, for example.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.

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You selected IC7800 addr.6AH and
19200 Bd. Press SET to write to the
memory, then press EXIT to go back to
the SETTINGS possibilities.
“SET OTHER ADDRESS” means that
you must add here a new type of ICOM
TCVR which is not defined in the table
(its address plus bitrate in Bd) to allow
communications with it.
Press ANTENNA SETTINGS. First
select ANTENNA SWITCH (No switch,
Standard). Use left or right arrows. If you
select some switch, 10 ports for different
antennas displays. Generally all of
antennas are allowed in every band
(green squares). To disable some
square select port (up/down), touch SET
for antenna name and then select band
(left/right). Press SET.
Four types of antennas for four different
bands were disabled.
Black square means disabled
combination.
Press EXIT to go back to SETTINGS
menu
BCD code (4 bits) is used for automatic antenna and BPF switching (see Antenna/BPF
connector on the Control panel (rear side of the PA). See section 7.9 for Control and
ANT/BPF connectors pin-out.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.

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Next SETTINGS position is for display
parameters. First choose the background
color. Scroll on it and choose the color
(left/right).
Press SAVE twice, then scroll to OWN
CALL.
Press SET for your call sign edit. The
keyboard displays.
Type your call sign and press ENT.
Use next lines and set brightness and
sound volume (use up/down and left/right).
Confirm with SAVE.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and working
frequency are visible on the display.
AUTO LED is ON.

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Press NETWORK SETTING and then
press ENTER.
Here the user has the option to set IP
Address, Network mask, Default
gateway, Port number.
User can enable or disable IP
parameter setting via LAN connection.
Next lines are for EBS (Electronic Bias
Setting) ON/OFF and for EBS level
selection.
We recommend EBS ON. See next
comment for more details.
Type of supported TCVR and
working
frequency are visible on the display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the display.
AUTO LED is ON.

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Electronic Bias Settings (EBS) is a significant feature of this power amplifier. It automatically allows
lower plate current after pressing the PTT, regardless of whether operating CW or SSB mode, when
no RF signal is present at the input. At the moment an RF signal is applied, the bias will
automatically change to its working value.
EBS level means level of the Input power where EBS starts working. Default EBS value is 0.1 W. We
recommend turning EBS ON. A significant feature of using EBS is PA operating temperature
reduction.
NOTE: If you are not using compression in your TCVR, or you are not speaking loud enough, some
syllables can be cut off. In such a case you should turn OFF the EBS.
The next two settings allow deletion
of the manual user settings of the
amplifier tunings for a single band or
for all bands.
Settings in all segments will return to
the factory default values (for 50
Ohms).
In the next line you can define
working mode of the blower. In the
first mode speed depends on the PA
temperature (TEMP), In PTT mode
the speed increases to maximum,
and the ALLWAYS mode means
maximum speed all the time during
PA operation (recommended for DIGI
modes).
Press SAVE to write the mode to the
memory.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.

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The INFO settings allows viewing all
of the previous PA INFORMATION
screen plus the addition of one more
touch key to enter the UPGRADE
mode.
UPGRADE touch button should
ONLY be used if the EEPROM or
firmware files (or both) will be
upgraded. In such a case ask the
dealer or manufacturer for the exact
procedure.
5.3. Preparing for operation
In STBY the amplifier is in bypass-mode and your transceiver is directly connected to
the antenna. Maximum allowed power in bypass mode is 200 Watts! The bypass RF
power is displayed if PA is in standby mode.
To turn PA ON press ON/OFF button on the front panel (black one) and hold it abt. 1 second. PA
will start tube heating. It will take 180 seconds. Turning PA ON is possible ONLY from the home
screen! If you have other display active, press EXIT more times to go back to the home screen.
(These same functions are also available on the OM Power Remote Control PC Application)
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.
Type of supported TCVR and
working
frequency are visible on the
display.
AUTO LED is ON.