Service manual

GE MEDICAL SYSTEMS PROPRIETARY TO GE
D
IRECTION , REVISION
5-18 Section 5-6 - Circuit Boards Descriptions
5-6-1-4 Receive Board
Sub-system receives and amplifies each echo signal. Then, all echo signals are outputted to the DBF
Assy.
The RXB ASSY can amplify the echo signals. So, the echo signals are received by a RXB ASSY under
appropriate control. The RXB ASSY are inserted into Nest box, which is composed of BACKPLANE and
other boards.
The RXB ASSY have main three blocks: TR Switch, Pre-amp and Gain Control and Mode control block.
The Transmit/Receive Switch protects the receive amplifier from high voltage transmit pulse the RXB
ASSY amplifies the echo signals. The mode control block selects a maximum gain code via dedicated
control signals from FEC.
The analog voltage signal provided by Gain Control block gives total amplified gain.
The block diagram above of the RXB ASSY for a received signal is given. Actually, there are 48 echo
adaptive channels in the assy.
The Pre-amp block consists of Low Noise Amplifier (LNA) which amplifies the RX Signal by fixed Gain
and Time Gain Control Amplifier (TGC).
The Pre-amp block is controlled by totally 4digital signals and an analog signal. In digital, One for input
impedance alternative low or high mode, another (3 bits) for choice of maximum gain code.
Figure 5-14 Receive Board
TR Switch Pre amp/ VCA Limiter
TR Switch Pre amp/ VCA Limiter
TR Switch Pre amp/ VCA Limiter
CONTROL
5V
1.4V
5V Supply
CON/TX Board DBF Board
48
48
0
1
47
REF GENERATOR
2.5
V
3.6V
5
Control Signal from FEC
IIC Bus
EEPROM