Bridge-Mono Operation; Parallel-Mono Operation; Terminator Module; Display Module - Crown Macro-Tech 5002VZ Reference Manual

The VZ mode switch (S700) has four positions which
control how the articulated supply functions. (Two of the
four switch positions are identical because there are
only three VZ modes.) In the VZ position, the supply will
automatically change as needed depending on the sig-
nal demands. In the Lock Low position, the supply stays
in high-current mode and cannot switch into high-volt-
age mode. In the "VZ-ODEP" position, the supply oper-
ates as it would in the VZ position unless the ODEP limit
is reached. If the ODEP limit is reached, the supply will
be locked into high-current mode to lower the thermal
dissipation of the output devices until it is cools enough
to return to normal VZ operation.
The fan control circuit (U713, U707B, U712 and Q706)
uses the ODEP thermal information to control the speed
of the fan. The summation of the ODEP signal and the
heat sink temperature is used to determine its speed.
In order to reduce the turn-on current needed by the
power transformers, a "soft start" circuit is provided
(U701B, U701A, U111, U700 and Q701) which limits
the maximum start-up current to less than 22 peak amps
per channel with 120 VAC mains. The primary voltage
is ramped up to the full voltage, then relay K700 closes
across triac Q701 for normal operation.

5.3.2 Bridge-Mono Operation

By setting the back panel stereo/mono switch to
BRIDGE MONO, the user can convert the Macro-Tech
5002VZ into a bridged mono amplifier. With a signal ap-
plied to the Channel 1 input and the load connected
between the positive output terminals of Channel 1 and
Channel 2, twice the voltage output of a single channel
is achieved.
The Channel 1 output feeds the Channel 2 error amp
(U205). Because there is a net inversion, the Channel 2
output is out of polarity with Channel 1. This produces
twice as much voltage across the load. Each of the
channel's protection mechanisms work independently
and both IOC indicators are operational.
Page 32
Macro-Tech 5002VZ Power Amplifier

5.3.3 Parallel-Mono Operation

With the stereo/mono switch set to PARALLEL MONO,
the output of Channel 2 is paralleled with that of Chan-
nel 1. A suitable jumper capable of handling high cur-
rent must be installed to gain the benefits of this
operating mode. The jumper should be connected
across a positive output terminal from each channel.
The signal path for Channel 1 is the same as for stereo
operation. The signal for Channel 2 is fed from the same
source as for Channel 1 and is paralleled at the input to
the error amplifier (U105 and U205). A signal from the
current sense circuit is also sent to the Channel 2 error
amplifier giving Channel 2 an electronic ballasting re-
sistor to better match the two outputs. In Parallel-Mono
mode, twice the current of one channel alone can be
obtained. Each of the channel's protection mechanisms
work independently if a fault occurs and both IOC indi-
cators are operational.

5.3.4 Terminator Module

The terminator module provides a high-frequency load
to the amplifier in order to maintain stability. It includes a
current sense circuit (U750) which is used for the I
display and in the Parallel-Mono mode.
I
Limit

5.3.5 Display Module

On the display module there are seven indicators. The
amber Enable LED shows that the low-voltage supply
is enabled. The green SPI/IOC LED is driven by Q502
from the output signal and flashes with the output signal
at normal brilliance. When the amplifier reaches early
clipping, the LED driven by Q504 will flash brighter in-
dicating an IOC event. The amber ODEP LED driven by
Q500 normally lights at full brilliance and diminishes
when thermal-dynamic power reserve drops. This LED
will stay off if the channel is put in standby. The two-
color I / I LED flashes green when U500, U501
Load Limit
and Q505 see output current. It turns red when the
amplifier's maximum current output is achieved.
/
Load
Reference Manual