Mechanics & Electronics ME750-FD User manual
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C O N T E N T
1.0 General overview .........................................................3
2.0 Specifications............. .................................................5
3./a Front Panel... ................................................................6
3./b Rear Panel ....................................................................8
4.0 Installation....................................................................9
5.0 Troubleshooting ........................................................10
6.0 Drawings......................................................................12
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ATTENTION!
Please read this manual carefully before operating the equipment!
The Linear Amplifier is easy to use, and damages can be avoided by following the
instructions stated below. Incorrect use may cause the loss of warranty.
1.0 G E N E R A L O V E R W I E W
The Linear Amplifier is produced by M+E Mechanics & Electronics Inc.
During the design of the ME series, the main point was to construct Linear Amplifiers for HF, VHF,
and UHF amateur bands with similar mechanical measures and appearance, using ceramic valves
easily available on the market.
The ME500-1500 series utilises the advantages of the ceramic valve, and considering the power
output and price, is a worthy competitor of similar equipment on the market.
The Amplifiers are protected by modern circuits,- specially designed and used only by our
company,- providing a very high level of protection. With their low input power and high efficiency
they fulfil the requirement of an improved amateur station.
To use the Amplifier with satisfaction and utilising all it’s advantages, please read the following
general instructions carefully:
1.1 Do not use higher driving power as given in the instruction manual. During SSB transmission
the ‘MIC GAIN’ control of the TCVR is not fit for the TCVR is regularly activating the protection
of the Linear.
In case of lately designed equipment the output power of the TCVR is control of the radio.
1.2 The SWR protection of the Linear is inactive during STBY mode.
In case the SWR > 1:3 in QRO mode, the protection is active, the PA can be use only with
Antenna Tuner.
1.3 The required power supply is 230V 50Hz according to the EU standard. Verify that the rating of the
line fuses located in the rear panel fuse holders is suitable for the AC line voltage you will be using.
The fuse should be the glass cartridge slo-blow type. The rating should be 10-12 Ampere by 230V AC.
1.4 The Amplifier is constructed with a forced air cooling. Free air movement has to be provided
and considered during positioning.
Do not operate the Amplifier in excessively warm locations or near heating vents or radiators. Be sure
air can circulate freely around and through the Amplifier cabinet, and can provide an unobstructed air
inlet for the internal cooling fan. Do not place any books, magazines, manuals, or equipment that will
impede the free flow of air near the sides and the hot air exhaust holes located on the top of the
cabinet. The internal fan allows an air flow of approximately 100-150m3/hours. The exhaust air
becomes quite warm at high power levels. Do not position any heat-sensitive objects in the exhaust
airflow path.
1.5 The PA is constructed with the following protection circuits and useful features:
-Heat up time checking circuit
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-Protection circuits (Ia, Ig1, temp, SWR>3)
-Temperature dependent ventilating speed control
-Cooling fans (2 pcs)
-Function and status indicator LEDs (6 pcs)
-1.8KVA transformer
-3-way PIC controlled sequencer
-4LED bargraph on new front page version (PWR out, VSWR, Ig, Ia)
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2.0 S P E C I F I C A T I O N S
ME750-FD 4/6m DUOBANDER
Frequency coverage 50-52 MHz, 70-72MHz switchable
Operating modes ALL mode
Output Power 1000 W pep on both bands, common outp
Driving Power 0-50W max. on both bands.
Input WSVR max 1:1.5 on both bands.
In/Out impedance 50 Ohm, separate input/bands
Valve(s) 2XGI7BT
T/R System SEQUENCER OPEN COLL. OK
Harmonic supression >50dB at 700W RF out
Intermodulation >35dB at 700W RF out
Protection Ia >1.0A
Ig1 > 250mA
VSWR > 3
Temp 75Co
Dimension 410X185X300 mm
Weight 25kg
Mains 220-230V/10A 50/60 Hz
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3/a FRONT PANEL
1. POWER ON
Main switch of the equipment.
2. ON LED
The LED indicator glows when the Linear is switched on. Doesn’t lit in case the 15V DC – supply
for the protection circuits and antenna switch - is missing.
3. OVR LED
The blinking LED indicates the active stage of the protection circuit. The protection might be
active due to overdrive, IG1 higher as specified, SWR > 3, or any other case. (See
specifications)
If the protection is active, the TCVR power by-pass the PA. To reset the protection release the
STBY SWITCH, than push it again. The reason of the trouble has to be cleared first.
4.AIR LED
The indicator glows while transmitting and the T/R relay is switched on. Without driving power
the PLATE meter indicates the idle current of the PA.
5. OPR LED
Glows when the PA is ready for transmission. During heating up period, when the LED doesn’t
lit, the driving is blocked. The stby time is about 180 sec.
6.WAIT LED
Blinking during the heating up period, indicating that the heating is in progress. Required time
is abt. 180 sec, when the light goes out and the OPR led lit up.
7. QRO LED
Indicates the high power mode of the PA. Can be activated by the push-button below. In case
the mode is not active, only the TCVR power is on the aerial. (Small PWR STBY mode)
8. STBY SWITCH
The PA can be driven only if switch is ON, otherwise the TCVR power by-passes the PA (STBY).
In case the overload protection is active, switch to STBY, and switch ON again.
9. RF FORWARD POWER BARGRAPH
Indicate RF output power in KW.
10. REFLECTED POWER BARGRAPH
Indicate the reflected power in Watts.
11. Ig1/TEMP BARGRAPH
Indicate grid 1 current, when you push the TMP pushbutton indicate outlet air temperature in
Celsius.
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12. Ip/Ua BARGRAPH
Indicate the Ia current. When you push the HV pushbutton indicate the Ua voltage in KV.
13. Plate and Load knobs
Tuning knobs of the anode and antenna side capacitor. Used for tuning the PA for max output.
The position of the capacitors is different on 4m an 6m!
14. 4/6m SWITCH Switching the input/ output of the PA to 4m/6m. For QRP mode must switch to
real band. ( If you use bypass mode on 4m switch it to 4m, if on 6m switch it to 6m.)
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3/b REAR PANEL
1. 230V
Power cord fit for standard 230V-50/60Hz mains. The colour of the protective earth is
green/yellow.
2. FUSE1-2
Main fuses, 230V max. 10A.
3.FUSE3
HV fuse. 1A.
4.FUSE4
Fuse for the 18V AC. Value range 1.6A.
5. FAN 1
Cooling fan for the main transformer. 12V - 0.2A DC.
6.FAN 2
Cooling fan for the power valves. 12 - 18V/ 0.3A DC, or 230V AC 18W.
7. PTT
Connection for PTT RCA. The relays are closed by earth connection. Low voltage, low current
entry. Fit for open collector control as well.
8.INPUT
Input connection for the driver TCVR. 50 Ohm (“N” connectors on both bands,the 6m input is
on the center position.
9. OUTPUT
Aerial connection. 50 Ohm Common ant connector on both bands.(4&6m)
10. GND
Ground connection.
11. ALC
Option.
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4.0 INSTALLATION
4.1 Connect your TCVR’s to the Linear using a short, 50 Ohm coaxial cables.(different 4 and 6m
different inputs, 6m in middle position.
4.2 Connect your TCVR ground giving socket or better foot-switch to the PTT RCA socket on the
rear panel of the Linear, using a screened cable.
In case your TCVR has an open collector PA controller output, you can use it without
difficulties. The input of the PA PTT is low voltage low current input.
4.3 Connect your aerial to the OUT socket of the Linear.(6m ant if you working on 6m, 4m if you
choose the 4m band operation. VSWR must be better than 1:2 on both bands.
4.4 Using a flexible cable at least 6mm2,connect your PA to a suitable grounding point and to the
grounding point of the transceiver.
4.5 Connect the power cord to the mains and switch on the equipment. The ON led glows and the
WAIT led start blinking for a period of abt. 180 sec, during the heating period.
The readiness of the Linear is indicated by the OPR LED. If the PA was out of use for a longer
period (2- 3 month), it would be advisable to keep the PA heated without driving for a few
hours.
4.6 When the OPR LED is light push on the OPR switch. The PA is ready to work.Don’t forget
choose the wanted band with the 4/6m bandswitch!
4.7 Using the tuning mode of the TCVR (CW) give driving power to reach 200-400 mA indication on
the Ip bargraph. Tune for maximal output power with Plate and Load knobs. (position: Plate “
”, Load “ ” on case 50.1 MHz and 50 Ohm antenna, set about to the knob position
” “ plate, and “ “ position load on case 4m band. Tune fine to max output with the knobs
on case full drv input.
4.8 “ Increase the driving power until maximum anode current, than carry out fine tuning using
knobs. You can indicate the reflected power on RFL LED bargraph.
REMEMBER THIS AMPLIFIER DOES NOT REQUIRE MUCH DRIVE POWER. SO START WITH
LOW DRIVE POWER, AND THEN TUNE TO RESONANCE AS OUTLINED ABOVE.
4.9 Check the grid current. Reduce the driving power or make fine tuning in case the grid current
would exceed THE SPECIFIED VALUE!
4.10 During SSB transmission the peak power of the TCVR may exceed the allowed maximum
driving power of the transceiver! Use The POWER knob on the TCVR in this case.
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5.0 TROUBLESHOOTING
Malfunctions are mostly due to improper handling, overload or similar reason.
5.1 Do not use higher input power as stated in the specification. The grid protector circuit will
usually safe the power valves, but OVERLOAD alarm will appear regularly. This may happening
often in SSB mode, especially in case of old transceivers, when the output power in SSB mode
is not adjustable. The ‘MIC GAIN’ knob is not fit for power reduction!
5.2 INPUT SWR
The input SWR of the Linear is lower than 1:1,5.
A well adjusted TCVR will tolerate these values without any trouble.
5.3 OUTPUT SWR
The protection of the Linear will block the transmission in case the SWR of the aerial exceed
1:2.
5.4 FAILURES
The PA not turn on, nothing happens ON switch is pushed.
External AC wiring, fuse or circuit breaker may be open.
Amplifier power cord not in place - cover safety interlock open.
Fuse F1, F2, F4 open or missing - check fuses with an ohmmeter.
The PA turns on but no HV is indicated on the Ip bargraph.
Possible HV circuit fault. (check the F3 fuse ( 1A on rear panel.)
HV sampling resistor in power supply damaged. (HV panel R23,0.47 Ohm).
No idle current when you push the PTT (about 120 mA on the Ip bargraph).
Not Ua voltage.(Push the red HV knob.If anode voltage is missing, check F3 HV fuse
(1 A fuse on rear panel.)
The idle current is too low or too high.
you can set the needed value with P6 poti on UCU-01 panel if necessary).
You can indicate normal Ip current on LED bargraph when drive PA,(6-750Ma) but no output
power.
Check the output coaxial relay.
5.5 LIMITED WARRANTY
The M+E Mechanics & Electronics will warrant that the equipment will perform substantially in
accordance with the written materials for a period of 12 month from the date of receipt and will
be free from defects in material and workmanship under normal use. This Limited Warranty is
void if failure of the equipment has resulted from accident or misapplication, any kind of
modification done, overvoltage, shipping, and in case the damage of the power valves.
Warranty repairs done only on the base of the M+E Mechanics & Electronics.Return cost will
be covered by the owner.
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5.6 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
SWITCH DEFEATED. BEFORE REMOVING THE TOP COVER MAKE SURE THE AC LINE POWER
CORD HAS BEEN DISCONNECTED FROM THE AC POWER SOURCE. ALLOW A MINIMUM OF 5
MINUTES TO ELAPSE BEFORE REMOVING THE TOP COVER AFTER POWER HAS BEEN
REMOVED. THIS IS NECESSARY TO ALLOW THE PLATE VOLTAGE FILTER CAPACITORS TO
BLEED DOWN TO A SAFE LEVEL.
Before operating this unit ensure that the protection conductor (green/yellow wire) is
connected to the ground (earth) protective conductor of the power outlet. Do not defeat the
protective features of the third protective conductor in the power cord by using a two
conductor extension cord or a three-prong/two-prong adapter.
Before operating this unit:
1. Ensure that the instrument is configured to operate on the voltage available at the power
source. (See Installation Section)
2. Ensure that the proper fuses are in place in the amplifier's AC line fuse holders located
on the rear panel.
3. Ensure that all other devices connected to or in proximity to this amplifier are properly
grounded or connected to the protective third-wire earth ground.
If at any time the amplifier shows visible damage, has sustained stress, emits a foul smell,
fails to operate satisfactorily, it should not be used until its performance has been checked
by qualified service personnel.
Connect a good earth or water pipe ground to the ground post on the rear of the Amplifier. Use
the heaviest and shortest connection possible. Before you use a water pipe ground, inspect the
connections around your water meter and make sure that no plastic or rubber hose
connections are used. These connections interrupt the continuity to the water supply line.
Install a jumper around any insulating water connectors you may find. Use heavy copper wire
and pipe clamps.
It is best to ground all equipment to one point at the operating position and then ground this
point as described above.
5.7 SAFETY INTERLOCK SWITCH
While the Amplifier's top cover is in place, the interlock switch closes to allow AC line voltage to reach
the power transformer. When the top cover is removed, the interlock switch opens and disconnects the
line voltage. This does not discharge the bank of power supply filter capacitors. Be sure to allow the
filter capacitors to discharge before you touch anything inside the Amplifier. You can select the High
Voltage function of the Multimeter to check the high voltage potential.
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