Crown k1 Supplementary Manual
K Series Service Manual
Rev A.
3-4 Theory
©1999 Crown International, Inc.
plifiers are incorporated with a current limiting pro-
tection circuit. The output current is sense by the cur-
rent sense resistors found in series with the BCA filter
inductors. The voltage dropped across these two re-
sistors is sent back to U106A and U106B. The volt-
age windows for U106A and U106B are set by the
dropping resistors R303/R310 and the zener diodes
D113/D114. The window voltage is ±0.7V. The out-
puts of the window comparator are normally +0.6V.
This positive voltage is sent to U107A, an optically
coupled gate. Pin 2 of U107A is tied to B1-7 and as
long as pin 1 is positive the device conducts. The
output is an inverting stage so when its input is posi-
tive its output will be negative. If the current limit de-
tector switches states (becomes negative) pin 1 is
negative and pin 7 becomes positive.
tection circuit. The output current is sense by the cur-
rent sense resistors found in series with the BCA filter
inductors. The voltage dropped across these two re-
sistors is sent back to U106A and U106B. The volt-
age windows for U106A and U106B are set by the
dropping resistors R303/R310 and the zener diodes
D113/D114. The window voltage is ±0.7V. The out-
puts of the window comparator are normally +0.6V.
This positive voltage is sent to U107A, an optically
coupled gate. Pin 2 of U107A is tied to B1-7 and as
long as pin 1 is positive the device conducts. The
output is an inverting stage so when its input is posi-
tive its output will be negative. If the current limit de-
tector switches states (becomes negative) pin 1 is
negative and pin 7 becomes positive.
The output of U107A is routed to U6A (exclusive NOR)
and as long its inputs are negative the output of U6A
will be positive allowing the modulating network (U101
and U103) to output signal. If the output of U107A
goes positive the output of U6A goes negative thus
disabling the modulating circuit.
and as long its inputs are negative the output of U6A
will be positive allowing the modulating network (U101
and U103) to output signal. If the output of U107A
goes positive the output of U6A goes negative thus
disabling the modulating circuit.
3.13 Overlap Correction and Adjustment
The Overlap adjustment corrects for DC shift in the
Triangle waveform. In order to track thermal variations
the Overlap adjustment potentiometer (R25) is located
on each of the Output assemblies. A positive DC volt-
age is routed from the wiper arm of R26 to the Tri-
angle wave gain stage. This DC voltage varies the
DC component of the 250KHz waveform.
Triangle waveform. In order to track thermal variations
the Overlap adjustment potentiometer (R25) is located
on each of the Output assemblies. A positive DC volt-
age is routed from the wiper arm of R26 to the Tri-
angle wave gain stage. This DC voltage varies the
DC component of the 250KHz waveform.
3.14 Display Circuitry
The
IOC (Input Output Comparator) circuit uses the
error signal from the error amplifier (U100D). With a
window of ±0.3V U102A and U102D have a positive
output. This in turn biases off D105 leaving a positive
voltage on the base of Q103. If an error signal ap-
pears the ±0.3V window is overcome and the com-
bined outputs become negative. This results in the
output of U102C to go negative and in turn biasing on
Q103. As Q103 biases on, E102 illuminates.
window of ±0.3V U102A and U102D have a positive
output. This in turn biases off D105 leaving a positive
voltage on the base of Q103. If an error signal ap-
pears the ±0.3V window is overcome and the com-
bined outputs become negative. This results in the
output of U102C to go negative and in turn biasing on
Q103. As Q103 biases on, E102 illuminates.
A sample of the amplifier output (Fo CH1) is sent to
U2A and U2B. This audio waveform sample then
drives Q102 varying the current to the SPI (Signal Pres-
ence Indicator) LED E101.
U2A and U2B. This audio waveform sample then
drives Q102 varying the current to the SPI (Signal Pres-
ence Indicator) LED E101.
The compressor circuit is initiated by either the
IOC
initialization signal or The Thermal Limit Control sig-
nal. When initialized U1B output (pin 7) becomes posi-
tive. After routed through the non-inverting input of
U1A this positive signal turns on E100.
tive. After routed through the non-inverting input of
U1A this positive signal turns on E100.
The signal used to switch on the Power LED comes
from the Power OK control circuit. As this lime goes
positive Q1 conducts lighting E1.
from the Power OK control circuit. As this lime goes
positive Q1 conducts lighting E1.
3.15 Control Circuitry
After initial power supply power up the outputs of U7C
and U7D become positive (+1.2V). The output of U7
C and U7D is routed to two places: 1.) the first is the
Power OK LED and 2.) then the Modulator able/dis-
able comparator, U108A.. This positive logic signal
causes the output of U108A to become positive
(+1.3V) which next biases on Q102. With Q102 bi-
ased on the collector/emitter voltage is low (0.6V).
Since U6A is a NOR gate and both inputs are low the
output is a logic high allowing the modulator circuits
(U101 and U103) to pass signal.
and U7D become positive (+1.2V). The output of U7
C and U7D is routed to two places: 1.) the first is the
Power OK LED and 2.) then the Modulator able/dis-
able comparator, U108A.. This positive logic signal
causes the output of U108A to become positive
(+1.3V) which next biases on Q102. With Q102 bi-
ased on the collector/emitter voltage is low (0.6V).
Since U6A is a NOR gate and both inputs are low the
output is a logic high allowing the modulator circuits
(U101 and U103) to pass signal.
There are four functions that can disable the modula-
tor circuit and disable the amplifier. These four inputs
all effect the control line connected to pin 5 of U108A.
The normal logic levels for this control line are: ON/
0.6 and OFF/–14). The four control functions are:
tor circuit and disable the amplifier. These four inputs
all effect the control line connected to pin 5 of U108A.
The normal logic levels for this control line are: ON/
0.6 and OFF/–14). The four control functions are:
1. Initial Turn On Delay (U8A). On initial turn on the
control line to U108A is logic low causing the modu-
lator to be disabled. Once the capacitor found within
the RC timing network (C161/R302) charges this com-
parator stage switches states allowing the Modulator
to conduct. (Normal logic levels are ON/0.6 and OFF/
-14).
control line to U108A is logic low causing the modu-
lator to be disabled. Once the capacitor found within
the RC timing network (C161/R302) charges this com-
parator stage switches states allowing the Modulator
to conduct. (Normal logic levels are ON/0.6 and OFF/
-14).
2. Over Temperature (U108B). In the event the ampli-
fier overheats the output of U108B switches states
disabling the Modulator.
fier overheats the output of U108B switches states
disabling the Modulator.
3. Proportional Vcc (U8C). The Proportional Vcc cir-
cuit monitors the ±Vcc power supplies. In the event
that the line voltage drops to far below the rated line
voltage (causing erratic operation) U8C switches
states disabling the Modulator circuit.
cuit monitors the ±Vcc power supplies. In the event
that the line voltage drops to far below the rated line
voltage (causing erratic operation) U8C switches
states disabling the Modulator circuit.
4. Current Limit (U108D).
If the amplifiers current limit is exceeded because of
low impedances or a short circuit loading, U108D
switches states and disables the modulator circuit.
low impedances or a short circuit loading, U108D
switches states and disables the modulator circuit.