Continental Electronics 816R - Overload and Recycle Circuits; Power Failure Recycle

A5R7 produces a voltage that is applied to relay
A11K6 through resistor A11R66. When SCR
A2A2Q5 is gated on, a ground is applied and relay
A11K9 is energized. Each relay is adjusted to trip
at a factory preset current level. The relay contacts
are in series with plate control relay A8K3. If an
overload occurs, the corresponding relay trips and
de-energizes relay A8K3, removing plate power
from the transmitter.
Overload and Recycle Board, A2A5.
Overload and recycle board A2A5 contains circuits
that provide overload indication and memory,
automatic power on recycling, and filament control
circuit interlock status (Refer to Schematic
180167).
When an overload occurs in the PA plate, PA
screen, or VSWR circuits, a 28 V de pulse is
supplied to the appropriate SCR Q4, Q7, or Q8.
The SCR latches and lights its associated LED
indicator on the Al panel to indicate which
overload has occurred. All indicators that have
been lighted by an overload function remain lighted
until FAULT RESET switch A1S11 on the main
control panel is pressed. Plate voltage is removed
by overload relays Al 1K6, Al 1K7, or Al 1K9. The
28 V de pulse that triggers the SCR is
simultaneously routed to the recycle circuit via
diodes CR9, CR11, or CR12 to be used to
automatically restart the transminer.
The automatic recycle circuit provides a timed
restart pulse for up to four overload occurrences
within a 30-second period. The card as shipped will
allow only two restart pulses in a 30-second period.
However, it may be reconfigured to allow four
restart pulses in a 30-second period by removing
the jumper between terminals A and B on the card
and replacing it between A and C.
The auto recycle begins when the 28 V de pulse is
applied to the base of transistor Q2 causing it to
conduct. The output of Q2 is fed to timers U1 and
U4. Timer U1 provides a 0.5-second delay, then
triggers timer U3 which generates a 0.5-second
output pulse. This pulse is fed through gate U2A to
inverter Q3 which causes Q6 to conduct and charge
capacitor C22. The charging current of capacitor
C22 momentarily energizes relay KI which closes
the PLATE ON circuit through switch S2. The
charging current of capacitor C22 also flows
through RECYCLE PULSE indicator LED CR6
giving an indication of the recycle circuit operation.
Gate U2D conducts the output pulse from timer U1
to counter U5. Counter U5 counts the number of
recycle pulses and provides a logic 1 output at
terminal C when four pulses have been received.
Depending on which terminal has been strapped to
terminal A, two or four recycle attempts in a
30-second period will close gates U2A, U2B, U2C
and U2D and prevent any further attempts by the
card to restart the transmitter. RECYCLE
LOCKOUT indicator LED CR2 will light to
indicate this condition. When the 30-second period
of time has elapsed, a pulse is generated, inverted
by transistor QI, and applied to U5 to reset it to
zero. This clears the memory and allows another
sequence to begin. If the maximum count of two or
four pulses has not been received in the 30-second
period, the timer will also reset the counter
automatically.
AUTO-RECYCLE switch S2 may be used to
disable the auto recycle card when desired. This is
usually done during tune-up or maintenance
procedures. RECYCLE TEST switch SI may be
used to test the automatic recycle circuit during
maintenance procedures by simulating an overload
pulse at the input to the recycle circuit.
Power Failure Recycle Board, A8A1.
In the event of momentary loss of primary power,
the power failure recycle circuit restores the
transmitter to operational status. Capacitor C3
maintains current flow through time delay relay
A8K4 keeping the time delay circuit active for
short term power outages and a separate circuit
provides a momentary ground at pin 10 when
power is restored. The momentary ground is
applied to capacitor A2A5C22 and the charging
current of this capacitor pulls relay A2A5K8 in and
initiates the power ON command.
The latching relay permits local or remote selection
of manual or automatic power control. The latching
relay is connected to the remote control panel
through terminal board A10A2. A 28 V de signal
applied by local control switch A1S5 or through
remote control interface board will latch relay K2
in one of two stable states. AUTO PWR
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