Sanyo ACI-A Training Manual page 13

2-6 AFT
This chassis employs two kinds of the AFT circuit, it's called the Digital AFT and the Trace
AFT.
The digital AFT operates as the hardware AFT in the tuner circuit. Every channel selection,
the CPU reads out the tuning data from the memory and then changes tuning voltage output
from pin 8 to obtain the best tuned picture.
The trace AFT is to prevent the drifting of receiving condition caused by the temperature
etc. The CPU monitors the AFT S-curve signal input to pin 13 and maintains the correct
tuned picture by controlling the output tuning voltage.
.
Digital An
(1)
'w
(2)
(3)
(4)
The CPU outputs tuning voltage(Start value) which is subtracted with the step as table-1
from the stored tuning voltage data in the memory and waits for 240ms.
II*
When the AFT voltage is less than 1.5V, go to step (4).
III*
Other than the above, go to step (2).
Increase the tuning voltage along with table-2a until the AFT voltage reaches less than
1.5V. Go to next step.
Decrease the tuning voltage along with table-2b until the AFT voltage reaches more than
2.OV. Go to next step.
The CPU judges that the sync. signal is existing or not by detecting the voltage on pin
46,
If the CPU detects a low voltage on pin 46, go to step (2).
If the CPU detects a high(5V) voltage on pin 46, complete the digital AFT operation and
go to the Trace AFT stage.
Trace Am
After completing the digital AFT operation, the CPU switches to the trace AFT mode.
(1)
(2)
'L
(3)
If the AFT v;ltage ii more than 3.OV and the IF ident. signal is detected, the CPU
increases the tuning voltage along with table-3.
If the AFT voltage is less than 2.OV and the IF ident. signal is detected, the CPU
decreases the tuning voltage along with table-3.
In the preset mode and fine tuning mode, this function does not operate.
'"L
Tablel Substructed steps
Table-3 Tuning spesd of Trace AFT
~=
Table-2 Tuning apeed of digital AFT
(a) High spead (steps/10msec.)
~
(b) Mid spead (steps/10msec.)
~
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Training Manual AC I Chassis