Nautel XR6, Troubleshooting Manual, Page: 69 / 291

XR6/XR3 Troubleshooting Manual Detailed Circuit Descriptions
Issue 3.0 2009-07-15 Page 2-1
Section 2: Detailed Circuit Descriptions
Refer to the functional block diagram: “XR Series Transmitter Block Diagram” on page 1-7 and high
level descriptions of the XR6/XR3 Operation and Maintenance Manual .
This section provides a detailed description of the transmitter’s key modules and assemblies,
including:
• Control/display PWB (NAPC147D) - see page 2-1
• RF synthesizer PWB (NAPE70C) - see page 2-4
• Interphase PDM driver PWB (NAPM10B) - see page 2-8
• Remote interface PWB (NAPI83/01A) - see page 2-13
• RF drive power supply PWB (62 V) (NAPS10B) - see page 2-18
• RF power module (NAP34A) - see page 2-19
• RF drive buffer PWB (NAPE77A/01) - see page 2-30
XR6/XR3 electrical schematics
The descriptions in this section all refer to the XR6/XR3 electrical schematics listed in Table 5.1 on
page 5-5 of the XR6/XR3 Troubleshooting Manual .
Control/display P WB (NAPC147D)
See electrical schematics Figures SD-5 through SD-8.
Carrier reference voltage
The Carrier Ref (A) output (J7-38) is applied to the interphase PDM driver PWB of each exciter to
generate the PDM drive pulse that ultimately controls the RF output of the transmitter. DAC U31, in
conjunction with microcontroller U22, establishes a dc reference voltage for the
Carrier Ref output.
The voltage is buffered through operational amplifier U27B and associated components.
Alarm threshold circuits
Certain parameters that are monitored by the control/display PWB can initiate an alarm indication
and appropriate transmitter control if an out of tolerance condition occurs.