Protech 66708 User Manual

PROTECH

www .protechaudio.com

®

11/07

66708

DUAL POWER SUPPLY

INSTALLATION & OPERATION MANUAL

The Protech Audio Model 66708 Dual Power
Supply is designed to provide regulated DC
power to the INTEGRA III SYSTEM audio
modules. The two separate 15-18 volt outputs are
designed to allow strapping together to create a
bipolar 15-18 volt configuration.

The Model 66708 is designed to be mounted in a
standard 19 inch wide EIA rack. The unit re­quires only 3.5 inches of vertical rack space.
The line cord plugs into a standard three prong
117VAC outlet.The front panel has five separate
indicators. The power on/off switch incorpo­rates a neon lamp, to indicate the presence of
power to the AC circuit. Each includes two LED
indicators. A green LED shows the output is
providing the required DC voltage. A red LED
indicates a fault condition.

Three separate protection circuits are designed
into the Model 66708. The AC circuit is pro­tected by a 3 amp slow-blow fuse.

Each DC output incorporates foldback/short cir­cuit protection. If the load attached to the output
is too great, the output volatage will be reduced.
If a short is applied to the output, the DC voltage
will reduce to zero volts, until the short is re­moved. The unit will then automatically in­crease the output voltage to the previously ad­justed level.
The Model 66708 also features local or remote
sensing of the regulated output voltage. The unit
is shipped from the factory strapped for local
output voltage. The unit is shopped from the
factory strapped for local sensing. The output
voltage at the rear terminal strip, will remain
constant, from no load to full load. The terminal
strip jumpers may be removed, and the sensing
terminals wired to a remote location. This ar­rangement will insure that the output voltage
will remain constant at the load. If the load is in
the same rack as the power supply, it is not
usually necessary to provide a remote sensing
configuration.

Protech Audio Corporation, 192 Cedar River Road, Indian Lake New York, 12842 Voice 518-648-6410 Fax [phone]

INSTALLATION

The Model 66708 is designed to mount in a standard 19" EIA
rack. The unit should be mounted in the bottom of the rack. A
minimum of a one rack space ventilation panel should be
mounted directly above the power supply, to provide adequate
ventilation.

Check that the AC line voltage and amperage rating are correct
before connecting the line cord. The rating should be 120VAC,
with at least 3 amperes of current available.

The DC connections should be made using a minimum of
18AWG wire. In the local sensing mode, three conductors will
be necessary. In the remote sensing mode, seven conductors
will be required. The connections are made as indicated in
Figure 1. After making all connections from the power
supply to the load, turn on the unit, and using a voltmeter,
verify that the voltages and the polarity are correct at the load.
The output voltages are adjustable via potentiometers, which
are accessible at the rear of the power supply chassis.

The actual steps for installation for the Model 66708 Dual
Power Supply are as follows:

1 - Mount the Model 66708 into the lowest available position in
the rack.

2 - Mount a single rack space (minimum) ventilation panel in the
rack, immediately above the power supply.

3 - Check the AC receptacle for proper voltage and current
rating before connecting the line cord.

4 - Plug in the line cord, and turn unit on. The neon power
indicator in the on/off switch should illuminate. The two green
LED DC voltage indicators should illuminate.

5 - Turn unit off, and wire the outputs to the load, observing
connection points as indicated in figure 1.

6 - Turn unit on, and using a DC voltmeter, measure the DC
voltage at the load. In the bipolar configuration*, the voltage
between GROUND and +VDC should measure 18 volts DC
positive. The voltage between the GND and -V should
measure 18 volts DC negative. The voltages may be adjusted
by using the potentiometers that are mounted on the rear of
the power supply chassis.

7 - Check the polarity of the voltage at the load. Between Pins
GND and +V, it should measure +18 volts. Between pins GND
and -V, the voltage should measure -18 volts.

Your installation is now complete. Continuous operation of the
Model 66708 is normal, and requires no further operations from
support technicians. There are no adjustments which must be
made on a periodic basis. However, periodic testing of the
overall system may be specified by the system designer.

CIRCUIT DESCRIPTION

The Model 66708 is a state of the art dual power supply. The
unit has two independent regulated outputs. Each output may
be used separately, or strapped together to form a bipolar
configuration. The bipolar arrangement is the type usually
used for the INTEGRA III SYSTEM.

The power transformer is toroidial in construction. This type of
power transformer emanates a much smaller AC field, which is
of great importance when working with low level audio ampli­fiers. The secondary of the toroid has two separate windings,
one for each power supply output.

There are two separate rectifier/regulator circuits in each Model

66708. The rectifier is a standard full wave bridge rectifier
followed by two 4700uf filter capacitors. The voltage regula­tion, and current sensing are derived by using an I.
C. regulator, the MC1723. The output current capability is
increased by the addition of 4 external pass transistors
(TIP120)
for each output.

NOTE: Power supply outputs are floating with re­spect to chassis and earth ground.

PROTECH

Power Supply Output is floating with respect to ground. It may be
necessary, depending on the individual installation, to provide a
ground strap from the card frame “GND” pin to power supply
ground.

REAR VIEW BACKPLANE/CARD FRAME ASSEMBLY

V+

GND

V-

GND ON

10

*

9

*

®

CONNECTION DIAGRAM FOR MODEL 66708

TO BE USED WITH 857B CARD FRAME.

Ground

OUTPUT #2

V- V-

SENSING

V+

OUTPUT #1

SENSING

EXTERNAL CONNECTIONS

Model 857B

8

7

**

6

5

**

MODEL 66708

NOTE:

V+

4

*

3

**

Leave Factory Installed
Sensing Jumpers In Place,
Unless Remote Sensing Is
Required

+18V

DETAILED

GND

-18V

2

VIEW OF

POWER

CONNECTOR

BELOW

1

*

*(ALL INTEGRA III SYSTEM
Amplifiers require

+15-18VDC)

Page 2

1.5"

GND
LIFT

16.5"

*Space used for additional connectors or trimpots as needed for application

1.5"