Transformer Thermal Protection; Power Supply Fuses - Crown Macro-Tech MA-5000VZ Reference Manual

Macro-Tech 5000VZ Power Amplifier
The undervoltage protection circuitry can also acti-
vate the standby mode. If the AC line voltage drops to
about 20% or more below the unit's rated voltage, both
channels will go into standby to prevent loudspeaker
damage that can result from brownouts and blackouts.
If dangerous subsonic frequencies or direct current
(DC) is detected in the amplifier's output, the DC/low-
frequency protection circuitry will put the channel in
standby to protect the loads and prevent oscillations.
Internal Standby Indicators
(For Qualified Technicians Only)
Although it is very unlikely that you will ever see an
amplifier channel unintentionally put in standby,
eight internal indicators (four per channel) are pro-
vided to help troubleshoot such a situation. They
are located inside the top cover of the amplifier.
DANGER: Electrical shock from this amplifier
can be lethal. The top cover should only be re-
moved by a qualified technician.
Four indicators are provided per channel, with six
on the main board and two on the control board.
Main board indicators include the following:
(1) DC/low-frequency protection, labeled "DC/LF,"
(2) fault, labeled "OUTPUT MOD FAULT," and (3)
standby, labeled "STBY." The control board indi-
cators help identify overvoltage conditions or
transformer thermal protection. These indicators
are labeled "OVER-VOLT/THERM. "
If the DC/LF indicator is lit, see what the indicator
does when you remove the input signal. If it turns
off, the problem is DC or subsonic material in the
input signal and you should refer to Section 3.3.4;
if it stays on, refer the amplifier to a qualified tech-
nician for service.
If the OUTPUT MOD FAULT indicator is lit, turn the
amplifier off, wait ten seconds and then turn it
back on. If the indicator stays off, try using the
amplifier for normal operation; if the indicator turns
on again, refer the amplifier to a qualified techni-
cian for service.
If the STBY indicator is lit, the installed PIP module
has put the channel in standby. For example, PIPs
controlled by the IQ System can be used to put
each channel in standby to conserve energy.
If the OVER-VOLT/THERM indicator is lit for one
channel, transformer thermal protection has been
activated. An overvoltage condition always
causes both indicators to light. If both indicators
are lit, test your AC mains voltage. If it is within
tolerance, you have somehow managed to acti-
vate thermal protection for both transformers (a
feat that is virtually impossible).
Reference Manual
The unit resumes normal operation as soon as the am-
plifier no longer detects dangerous low frequency or
DC output. Although it is extremely unlikely that you will
ever activate the amplifier's DC/low-frequency protec-
tion system, improper source materials like subsonic
square waves can activate this system.
The amplifier's fault protection system will put a chan-
nel in standby mode in rare situations where heavy
common-mode current is detected in the channel's
output. The amplifier should never output common-
mode current unless its circuitry is damaged in some
way, and putting a channel in standby mode helps to
prevent further damage.
The amplifier's transformer thermal protection cir-
cuitry is activated if the unit's transformer temperature
rises to unsafe levels. Under these abnormal condi-
tions, the amplifier will put the affected channel's trans-
former in standby mode. The amplifier will return to
normal operation after the transformer cools to a safe
temperature. (For more information, refer to Section
4.3.3.)

4.3.3 Transformer Thermal Protection

All Macro-Tech amplifiers have transformer thermal
protection. It protects the power supplies from damage
under conditions where transformer temperatures rise
too high. A thermal switch embedded in each trans-
former removes power to the channel if there is exces-
sive heat. The switch automatically resets when the
transformer cools to a safe temperature.
As long as it is operated within rated conditions (see
Section 6), it is extremely unlikely that your amplifier will
ever activate transformer thermal protection. One rea-
son is that ODEP keeps the amplifier working under
very severe conditions. Even so, higher than rated out-
put levels and loads with excessively low impedances
can generate more heat in the transformer than in the
output devices. These conditions can overheat the
transformers and activate the protection system.
Macro-Tech amplifiers are designed to keep working
when other amplifiers would fail. But even when the lim-
its of a Macro-Tech amplifier are exceeded, it will still
protect itself—and your investment—from damage.

4.3.4 Power Supply Fuses

An internal fuse protects the Macro-Tech 5000VZ's low-
voltage power supply. The low-voltage power supply
fuse will not blow unless something is wrong with the
amplifier. If the low-voltage power supply fuse blows,
refer the unit to a qualified technician for service.
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