Crown MARCO-TECH 5000VZ - Over-Voltage Protection; Over-Voltage Protection Purpose; Over-Voltage Sensing Method; U707 D Over-Voltage Response

C120
CHARGE
VOLTAGE
O 1
PULSEO
DC FROM
LVPS
,
¿11*11 III m
i
AMAHAM A HA II AltH
11 lili 1U Hl U
I
!
1
lili
l
1
i'**
i
O 1
SOFT-START
TRIAC
CONTROL
6 is ampfcfter shutdown vía power swiyit. The lower graph shows Q701
operatioñ (htgfcv = on) The longá?- &701 is on, the more the main
transformer fieltMs^fett^^üilá.
Any time a protection mechanism has acted and íhe condition then
clears, this entire process repeats.
Over-Voltage
One mode of amplifier protection is a shutdown ¡n the event of over-
voltage on the AC mains. This is sensed by the pulsed DC signal
produced by the full-wave rectifier in the low voltage supply.
R780 picks off the pulsed DC and U707D will, if the voltage ¡s too high,
shift its output to a low. When this happens the over-volt/therm red LED
on the control module lights and signal OV1 goes low to the main
module.
A low (over-voltage condition) on OV1 causes U211C to shift to a low
output. This low, through D1, causes C120 todischarge immediately.
This in turn causes the main relay to drop out, soft-start to reset, and the
±LL and ±LH to clamp audio drive. Over-voitage is a non-latching fault
condition.
Notes
Soft-start waveforms. Timel: power
switch on. Time 2: relay engaged.
Time 3: protective action occurs. Time
4: protective action clears, Soft-start-
up beginsagain. Time 5: relay
engages. Time 6: amplifier turned off
by power switch.
MA-5000VZ - 23