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6-4. The ACOM1500 Simplified Schematic Diagram
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See Fig.6-I ACOM1500 Simplified Schematic Diagram. * The 4CX1000A/8168 ceramic
and metal radial beam tetrode (V1) with plate dissipation of 1000W is grid-driven. It can
dissipate up to 1000W when forced air cooled and is specifically designed for class AB1 RF
linear amplifiers.
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
tube input capacitance. The swamping resistor Rsw is a termination load for this circuit
and can dissipate up to I00W of RF drive power.
Cathode resistors Rc create 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
and the screen grid voltage regulator in the events of
an internal tube flashover.
The combination LpI-RpI in the plate circuit is a VHF/UHF parasitic suppressor. DC plate
voltage is fed through chokes RFCI-RFC2 and the capacitor Cb3 blocks it from the output.
The output circuit comprises LPI, LP2, LL, CPI-CP3, and CLI-CL3 which form a classic Pi-L
network and suppress the harmonic frequency emissions. This tank is switched and tuned
over the bands by SIA-SIC and the air variable capacitors CPI, 2 and CLI, 2. The output signal
is fed through an additional VHF low-pass filter for frequencies above 55MHz (LfI, Lf2 and
Cf). Then it is passed through the vacuum antenna relay KI, wattmeter current transformer
TAI, and a high-pass filter RFCasw-Casw for frequencies below I00kHz, to the
antenna
switch and the three outputs. The chokes RFC3 and RFCasw keep track of the antenna relay
contact conditions and together with Casw prevent the plate supply from reaching the
antenna. RFCasw shunts the high voltage to ground should the DC blocking capacitor Cb3
fail. The resistor Rasw 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 suupply 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 are available from ACOM or from your dealer on
request.
6-5. Troubleshooting
See S.5-4 for the method of reading the auto-protection signatures. You can decode them
using the information below. *
The signatures are structured in two lines, three groups by six symbols for every one event of
auto- protection. The last event is numbered as IA-IB pair of lines, and the oldest one is
7A-7B.
The meaning of the first group is as follows:
a)
nA - the number of the trip;
b)
Next three symbols mean the following:
PN0 - tests made during Power-On procedure, before HV is ON;
PN2 - tests made during Power-On procedure, after HV is ON and
one second after
step-start is closed;
Содержание 1500
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