Acom 1006, Руководство по эксплуатации

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complicated and potentially dangerous operation. Should one of these fuses be blown, it may be indicative of
other failures. For this reason, we recommend this work be carried out by a trained service technician.
6-3. Tube Replacement
A single 4CX800A (GU74B) high-performance ceramic-metal tetrode manufactured by Svetlana is employed
in the amplifier. Replacement is a complicated and potentially dangerous operation. The idling plate current
must be adjusted after a replacement. For this reason, we recommend this work be carried out by a trained
service technician.
6-4. The ACOM1006 Simplified Schematic Diagram
See Fig.6-1 ACOM1006 Simplified Schematic Diagram.* The high-performance ceramic-metal tetrode
4CX800A (GU74B) from Svetlana (V1), with a plate dissipation of 800W, is grid-driven. The input signal from
the RF INPUT jack is fed through an input matching circuit, which comprises some components in the INPUT
PCB and Rsw. This circuit tunes out the input capacitance of the tube. The swamping resistor Rsw is a
termination load for this circuit and can dissipate up to 100W of RF drive power.
The cathode resistor Rc creates DC and RF negative feedback, thus stabilizing the gain and equalizing the
frequency response. The varistor VSsg in the screen grid circuit stabilizes the tube regime against dynatron
effects and protects its screen grid, and voltage regulator in the events of a flashover.
The combination Lp1-Rp1 in the plate circuit is a VHF/UHF parasitic suppressor. DC plate voltage is fed
through chokes RFC1-RFC2 and the capacitor Cb3 blocks it from the output. The output circuit comprises LP,
LL, CP, and CL1-CL2 which form a classic Pi-L network and suppress the harmonic frequency emissions.
This tank is tuned over the band by the air variable capacitors CP and CL1. The output signal is fed through
an additional VHF low-pass filter for frequencies above 55MHz (Lf1, Lf2 and Cf) that minimizes the second
harmonic in the region of 100-108MHz and increases higher harmonics suppression. Then the output signal
is fed through the vacuum antenna relay K1, wattmeter current transformer TA1, and a high-pass filter RFC4-
Ca for frequencies below 100kHz, to the antenna output.
The chokes RFC3 and RFC4 keep track of the antenna relay contact conditions and together with Ca prevent
the plate DC high voltage from reaching the antenna. The choke RFC4 shunts it to ground if the DC blocking
capacitor Cb3 fails. The resistor Ra protects the amplifier from charging Electro-static energy fed by the
antenna.
The PLATE CAPACITIVE DIVIDER and RF WATTMETER are the main sources of information for the control
circuit of the amplifier during the antenna impedance matching process. The control circuit is based on the
80C552 micro-controller from Philips.
All voltages are delivered from the MAINS&LOW VOLTAGE and HIGH VOLTAGE SUPPLY PCBs. The
control grid, screen grid and plate currents, plate cooling airflow temperature, reflected power etc. are
permanently monitored. Many software-derived protections are based on this information.
* Detailed electrical schematic diagrams and PCB layouts are available on CD-ROM from ACOM or from your
dealer on request.