Nautel XR12, Troubleshooting Manual, Page: 71 / 283

XR12 Troubleshooting Manual Detailed Circuit Descriptions
Issue 3.0 2009-07-28 Page 2-3
Sample monitoring circuits
Various parameters are applied to the control/display PWB for local (via the front panel's diagnostic
display) and/or external (via the remote interface PWB) monitoring. In most cases, these parameters
also have associated alarm detection circuitry, but it is not resident on the control/display PWB.
B+ sample
The B+ Sample input (J4-35) input is a dc voltages which represents the positive dc voltage applied to
the RF power modules as their high current voltage source. The input is filtered and buffered by
operational amplifier U7C and associated components. The
B+ Sample signal is applied to ADC U12
for application to the front panel's diagnostic display.
PDM drive
The PDM (A) (J4-9) and PDM (B) (J4-7) inputs are pulses which represent the PDM signal applied to
sides A and B of the RF power stage. The inputs are filtered through operational amplifiers U7B and
U11B and associated components.
PDM (A) Sample and PDM (B) Sample signals are applied to ADC
U9 for application to the front panel's diagnostic display.
Dc current
The Dc Current Sample input (J4-33) is a dc voltage which represents the dc current being drawn by RF
power modules. The input is filtered and buffered by operational amplifier U11A and associated
components. The
Dc Current Sample signal is applied to ADC U12 for application to the front panel's
diagnostic display.
PA voltage
The PA Volts Sample input (J4-31) is a dc voltage which represents the voltage applied to the power
amplifiers in the RF power modules. The input is filtered and buffered by operational amplifier U3C
and associated components. The
PA Volts Sample signal is applied to ADC U12 for application to the
front panel's diagnostic display.
Forward power
The Fwd Pwr Sample input (J1-3) is a dc voltage which represents the forward power at the
transmitter's RF output. The input is filtered through operational amplifier U2D and associated
components. A
fwd_pwr_sample signal is applied to ADC U9 for application to the front panel's
diagnostic display. The fwd_pwr_sample input is also applied to the remote interface PWB via the
external serial interface (microcontroller U22).
RF drive voltage sample
The RF Dr Volts Sample input (J4-39) is a dc voltage which represents the voltage supplied by the RF
drive power supply. The input is filtered through operational amplifier U3A and associated
components. The
bat_cur_sample signal is applied to ADC U12 for application to the front panel's
diagnostic display.