Troubleshooting - Acom 03AT Operating Manual

The input SWR of the AATU is being ensured below 1,67:1 during a tuning procedure by the swamping resistor R4
when the MOS FET Q1 is saturated. When it is cut off, the SWR could not exceed 1.6:1 too since at a very low
matching-circuit input impedance the SWR-situation is same as with a saturated transistor (50/30 = 1,67). Should the
input impedance be very high, the maximum SWR is limited by the reference load R10a,b (50
parallel to the matching-circuit input, i.e. the maximum SWR in this case could be (R4+R10)/50 = (30+50)/50 = 1,6.
So, the SWR presented to the transceiver is guaranteed below 1.67:1 regardless of the current position of the
matching circuit and for all possible tries during a tuning procedure. It is clear that after de-energizing both relays
KAT1 and KAT2 (after a tuning is finished), the AATU will present the tuned circuit input impedance directly to the
AATU RF input connector. Normally the tuned-circuit SWR will be below 1.5:1 (1.2:1 typically) for the tuning
frequency.
The RCU and remote unit control is made up by two separate control systems built based on micro-controllers from
ATMEL. In the RCU, the АТ90С8515 is employed at an 8MHz clock frequency while the remote unit utilizes the
AT89C4051 micro-controller at a clock frequency of 24MHz. They both make the most of standard solutions that are
clear from their schematic diagrams (see the Technical Supplement or contact your dealer for details).

5-4. Troubleshooting

The schematic diagrams as well as the PCB component layouts for all units in the RCU and remote unit of ACOM
03AT are shown in the Technical Supplement.
Should the RCU display indicate a problem, look up the message in the list below and before your contact the
service of your dealer (see S.1-2), try the recommendations about this message. The messages are listed in an
alphabetic order. After having performed the recommendations, try the function again.
In case of necessity of transportation, see S.6-3.
MESSAGE
* Action cancelled *
Stop RF & Press Esc
Ant.Voltage too High
ATU Disconnected
(the AATU RF input has been disconnected
in an emergency due to damage risk for
the RF Sensor)
ATU Not Responding
Cannot Disable RF
RECOMMENDATION
A tuning change has been rejected because of RF presence
at the AATU input. Stop transmitting BEFORE giving either
BYPASS, OPERATE or memory recall command that would
need switching of relays in the remote unit.
Check antenna presence at the AATU output.
Check the antenna condition and its SWR with no AATU
(BYPASS). Use another antenna. Reduce the RF power
fed to the AATU input.
Stop RF power for at least one second after each tuning,
prior to begin transmission. Reduce tuning power below 100W.
Prior to start tuning be sure the amplifier is bypassed (STBY).
Check whether the optic and power-supply cables between the
RCU and the remote unit are intact and if properly connected
(see connection instructions in S.2-3 & 2-4).
Check whether the 24VAC-supply voltage is present in the remote
runit. Check both fuses F1 & F2 (3.15A each – see S.5-2,b).
Reduce the tuning power below 100W. Any problem in the remote
unit is probable. Turn OFF the power supply for five minutes and
try again. If the problem would not disappear, the ribbon cable
between "ATU Control" and "RF Sensor" PCBs should be
examined. It is probable that the *RFON сигнал could not saturate
the MOS FET Q1 on the "RF Sensor" PCB. Such a repair should
be performed by a trained service technician.
Ω)
that is connected in
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