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BENCHMARK MEDIA SYSTEMS, INC.
BENCHMARK MEDIA SYSTEMS, INC.
The MicroFrame Series Instruction Manual
The MicroFrame Series Instruction Manual ............................................... 2
1.0 Introduction ................................................................................................................... 2
1.1 The MicroFrame Series ..................................................................................... 2
1.2 The MF-1............................................................................................................... 2
1.3 Modules................................................................................................................. 2
1.3.1 The PS-2......................................................................................................... 3
1.3.2 The LA-1 Line Amplifier............................................................................... 3
2.0 Unpacking ..................................................................................................................... 4
3.0 Installation..................................................................................................................... 4
3.1 Input Connections ..................................................................................................... 4
3.2 Output Connections................................................................................................... 5
3.3 Connector Assembly ................................................................................................. 6
4.0 Specifications ................................................................................................................ 6
Input Section: .................................................................................................................. 6
Gain Stage: ...................................................................................................................... 6
Output Section:................................................................................................................ 7
Metering: ......................................................................................................................... 7
Overall:............................................................................................................................ 7
5.0 Operation....................................................................................................................... 7
6.0 LA-1 Circuit Description .............................................................................................. 8
6.1 Overview ................................................................................................................... 8
6.2 Input Stage................................................................................................................. 8
6.2.1 Common Mode Filter......................................................................................... 8
6.2.2 The Input Buffers ............................................................................................... 9
6.2.3 The Differential Amplifier ................................................................................. 9
6.2.3.1 CMR Adjustment ........................................................................................ 9
6.2.4 Common Mode Voltage Range........................................................................ 10
6.3 The Gain Stage ........................................................................................................ 10
6.3.1 Gain with Power Matched Systems ................................................................. 11
6.4 The Signal Indicating LED ..................................................................................... 11
6.5 The Output Amplifier.............................................................................................. 12
7.0 PS-2 Circuit Description ............................................................................................. 12
7.1 Input Section ........................................................................................................... 13
7.2 Regulators................................................................................................................ 13
7.3 Adjustment Procedure ............................................................................................. 13
8.0 Service......................................................................................................................... 14
8.1 Troubleshooting Techniques ................................................................................... 14
8.2 Through-Hole Circuit Board De-Soldering............................................................. 15
8.3 Circuit Board Re-Soldering..................................................................................... 15
9.0 Warranty...................................................................................................................... 16 BENCHMARK MEDIA SYSTEMS, INC.
The MicroFrame Series Instruction Manual
1.0 Introduction
1.1 The MicroFrame Series
The MicroFrame Series consists of a modular rack mount chassis that is only 1 Rack
Unit high. The rack mount chassis in turn houses 16 modular amplifiers, with front panel
access, and two power supply electronics modules. The amplifier modules are 0.8"
wide and the power supply modules are 2" Wide, providing a total of 18 modules in a
16.8" wide chassis that is only 13 inches deep. The very high density utilized with the
MicroFrame Series provides for some of the most cost-effective use of real estate in
the industry.
1.2 The MF-1
The MF-1, a single rack-unit modular frame, is designed to house two power supply
modules, sixteen amplifier modules. This arrangement provides a redundant power
configuration from a common power transformer and power entry module. The IEC type
power entry device at the rear of the frame is a combination line filter, mains voltage
selector (120-240 volt 50/60 Hz operation) and power plug, allowing all international
power cords to be used.
Audio interconnect to the MF-1 is accomplished by one of two methods. If the frame
was purchased with IO connectors at the rear of the frame, wiring and connecting the
connectors to the frame achieves this goal. If the MF-1 was not purchased with IO
connectors at the rear of the frame, the connector plate at the back of the frame is
removed and connectorized audio wires are plugged directly onto the backplane/mother
board. 0.025" sq. posts are provided on the backplane with three ports to each amplifier
module position. Pre-Connectorized wire assemblies are available. These assemblies
consist of latching and polarized three-position Molex
�
SL housing and pins attached to a
length of #22 standard shielded pair, or #24 Mogami ultra flexible wire, ready for your
multi-pin connector at the rear of the chassis.
The MF-1 is finished with a high quality, black powder-coat. The nylon card guides and
the edge card connector, forming a secure arrangement suitable for mobile environments,
hold the modules in place.
1.3 Modules
The plug-in modules have attached front panels that correspond to the module itself, and
form a contiguous attractive front view of the frame. The finish on the panels is the same
black paint with white silk-screen graphics. Each module has a small, extruded
aluminum handle that has a bright anodize finish, and provides an ideal location for attaching labels as to the use of the module. Blank modules are available for unused
amplifier positions. An extender board is also available.
1.3.1 The PS-2
The PS-2 is the power supply module for the MicroFrame Series. It provides a linearly
regulated bipolar (�) 15 volts, at a maximum of 1.2 amps, to power the system. Linear
regulators are used to ensure ultra low-noise amplifier performance. Two power supply
modules are needed for each MF-1. The module has combining diodes at the output to
the backplane allowing redundant regulator operation. The MF-1 uses a common power
transformer and power entry module to feed the two PS-2 power supply modules.
Individual voltage trim potentiometers are provided to allow for load balancing between
the two supply modules. The power supply regulator modules have transformer
secondary fuses to isolate them from the transformer, in the highly unlikely event of a
catastrophic failure in one of the modules.
Operation of the MicroFrame Series should include forced air cooling, as 80 watts of
power may be dissipa