OM POWER OM4001HF User manual

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MADE IN SLOVAKIA
e-mail : [e-mail]
WWW.OM-POWER.COM
OM Power, s.r.o. 93030 Báč 126,
SLOVAKIA
Contact : [phone]
e-mail : om-po[email protected]
OM4001HF
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
2. SAFETY INSTRUCTIONS ................………………………………………………. 6
3. GENERAL DESCRIPTION ...............………………………………………………. 7
3.1. HF Compartment …………………………………………………………………. 7
3.2. Power Supply …………………………………………………………………. 8
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. OM4001HF Front Panel ……………….……………………………………………. 12
5.2. OM400HF Control ……………………………………………………………… 13
5.3. Preparing for operation ……………………………………………………………… 14
5.4. Operation mode …………….………………………………………………. 20
6. MAINTENANCE ...................……………………………………………. 22
6.1. Indication of Fault Conditions …………………………..………………………………… 22
6.2. Fuse Replacement ………………..……………………………………………. 24
6.3. Tube Replacement ………………..……………………………………………. 24

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6.4. Cleaning ……………..………………………………………………. 24
7. APPENDIX ………………………………………………………………. 25
7.1. Primary AC selection ……………….……………………………………………. 25
7.2. OM4001HF firmware upgrade ……………………..…………………………..………… 26
7.3. Control panel connectors pin-out ………………..…………………………….…… 29
7.4. Block Diagram of the OM4001HF Power Amplifier ………….…………..… 30
7.5. Troubleshooting ………………………………………………………………. 31
7.6. Factory reset ….………………………………………………………….. 33

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GENERAL INFORMATION
1.1. Introduction
he OM Power model OM4001HF is designed for all short wave amateur bands from 1.8 to 29.7 MHz
(including WARC bands) and all modes. It is equipped with a two ceramic tetrodes FU-728F.
1.2. Specification
1.2.1. Parameters
Frequency Coverage Amateur Bands 1.8 – 29.7 MHz including WARC
Power Output 4000+ 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 2 x FU-728F Ceramic tetrode
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 3kVA
Dimensions 485 x 200 x 455mm (width x height x depth)
Weight 46 kg
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
• The smallest and lightest 4000 W Power Amplifier on the market

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2. SAFETY INSTRUCTIONS
DANGEROUS HIGH VOLTAGE INSIDE!
The power amplifier is using high voltage up to 3300 V 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 OM4001HF 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 a professionally 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 a par of ceramic tetrode FU-728F in a grounded-cathode circuit (input into
control grids). The OM4001HF 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.
The output of the amplifier is a Pi-L circuit. The variable capacitors for TUNE and LOAD are seperate. This
enables the amplifier to be tuned exactly and makes it possible to easily return to the previously set
positions after band changes.
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Top view on the opened OM4001HF
Tetrode FU728F Blower Switch-ON Board
Output Pi-L Circuit Tuning Capacitor Front Subpanel Power Supply Board
3.2. Power Supply
This Power amplifier uses two 3 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 420 V (total

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3360V) @ 2.5A . 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 200mA. 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 OM4001HF
Mains Plugs Fuses 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 OM4001HF 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)
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 20-21 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. OM4001HF Front Panel
Front panel of the OM4001HF containing the touch TFT display , two control switches and three kmobs
for output circuit adjustment.
ON - Main Switch. After turning ON, a small 12V power supply 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. OM4001HF 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 touch screen is active for
some information, while the PA is still OFF!
INFO
Information display shows basic information about the PA: serial number, software version, time ON,
tube serial number and nominal Main voltage.
The information screen also provides an
overview of the last 20 warnings and faults:
UPGRADE touch button should ONLY be used
if the EEPROM or firmware files (or both) will
be upgraded. (sect. 7.2)
Press FAULTS.
Press EXIT to go back to the home screen.
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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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 to go back to the home screen.
The “Tube Heating Timer” is visible on the
display. Wait until the required 180 seconds
is complete before placing the amplifier in
OPERATE Mode.
After heating is completed, the PA will light
the STBY mode indicator and this Main
display will appear.
The LAST EV button allows the user to see
last faults.
Press BACK button for returning to Main
display
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 INFO button
A new button is visible – SET Umain. Press it.
Type in the actual setting of the primary
voltage tap and press ENT.
Press EXIT twice to go back to the Menu
display.
This is the actual physical setting of the primary voltage tap. It is just information for the
processor, which protects the permitted limits ( up or down) for a given value of the primary
voltage (protection circuit).
Pressing SETTING displays this screen.
Scrol by UP / DOWN to DISPLAY SETTING
and press SET
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.
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 SET for your callsign edit. The keyboard
displays.
Type your callsign and press ENT.
Use next lines and set brightness and sound
volume (use up/down and left/right).
Confirm with SAVE.
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.
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.
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.
Press MEAS button.
Pressing MEAS displays this screen.
Instantaneous values of the basic amplifier
parameters are displayed.
NOTE: You can FREEZE the screen and/or
allow constant monitoring.
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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By pressing the SERVICE button we are in
the SERVICE settings mode.
Scroll to selected line and press SHOW or
SET (depending on the line).
We selected last 20 FAULTS to show.
Press EXIT
Go to SET EBS1 AUTO and press SET.
PA will automatically set 20mA on the front
and back tube separately. When finished
successfully, you will see SET EBS1 AUTO OK
on the screen
You can try to do this manually, too.
Scroll to SET EBS1 MANUAL and press SET.
Use up/down buttons to set 20mA or as
close as possible value and press SAVE.
Similar ways EBS2 can be preprogrammed
(300mA by AUTO set).
Or another value of EBS2 by MANUAL Set.
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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Scroll to CALIBRATION Ip, Is and press SET.
Calibration will be done automatically.
Scroll to SWR PROTECT and press SET.
This feature allows user to switch OFF the SWR
This feature allows the user to switch OFF the
SWR protection.
We recommend to set it ON (SWR protection circuit will stay active, max. allowed SWR is 3:1). If OFF is
selected, higher SWR is allowed, but reflected power is measured. If it exceeds 350W, transmit will be
blocked.
Press EXIT.
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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5.4.Operation mode
Before switching to operation mode, check all connections between PA and TCVR.
We are now back in the Main display. We are
ready to go to the operation mode.
Press the black STBY/OPER button on the
front panel or button OPERATE on touch
screen display
We are now in OPERATE mode.
Note the light indicator on the touch Screen
has changed to OPERATE .
Press MENU.
Now try to press PTT (foot switch for
example).
We are now in TRANSMIT mode (without RF).
Note the new TRANSMIT light indicator on
the touch screen.
NOTE: The OM4001HF is tested at factory at a maximum output power of 4000W into a 50 Ohm load.
A unique Tuning table, with TUNE and LOAD values for every band, is supplied with each PA.
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.