Acom 1000 Simplified Schematic Diagram - Acom 1000 User Manual

6.4. ACOM 1000 Simplified Schematic Diagram

Please, see
Figure 6-1 ACOM 1500 Simplified Schematic Diagram
The 4CX800A (GU74B) Svetlana high performance ceramic-metal tetrode (V1) with plate dissipation of
800W is grid-driven. The input signal from the RF INPUT jack is passed through a broadband 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.
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 protects the tube 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
LP1, LP2, LL, CP1-CP3, and CL1-CL3 which form a classic Pi-L network and suppress the harmonic frequency
emissions. This tank is switched and tuned over the bands by S1A-S1C and the air variable capacitors CP1, 2
and CL1, 2. The output signal is fed through an additional VHF low-pass filter for frequencies above 55MHz
(Lf1, Lf2 and Cf). Then it is passed 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 supply
from reaching the antenna. 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.
Забележка!
Note!
Detailed electrical schematic diagrams are available from ACOM or from your dealer on
request.
Page 28 of 36 | S e c t i o n MAINTENANCE
User's Manual | ACOM 1000 | HF + 6m Linear Amplifier
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N O T E
August 2020