MT-4E VHF & UHF Receiver & Transmitter Instruction Manual
IM08-MT-4E-TXRX-P1162
VHF & UHF Hardware Tuning and Troubleshooting
19
transmitter Mainboard
Check the following test points on the transmitter mainboard:
Test Point
Signal Monitored
Typical Voltage
TP1
Voltage from Mothe13.8 VDC Line
+13.8 VDC**
TP2
Reg9.5 VDC from Motherboard
+9.5 VDC ± 5 %
TP3
USB Connector Power
+3.0 VDC or +5.0 VDC
TP4
Sw13.8 VDC Line from Front Panel Switch
+13.8 VDC**
Test Points are shown on the VHF / UHF Transmitter Jumper and Test Point Locator Illustrations.
If the test point voltages are within the specified range, it is most likely that the transmitter mainboard
is not the source of problem. Proceed to the following step.
Synthesizer and udB Modules
The synthesizer module and UDB are bound together through their communication link. At this level
of fault diagnosis it is not feasible to isolate the problem between two units.
If the transmitter front panel NORM/OFF/ KEY TX switch is set from the OFF position to the NORM
position and the two front panel LEDs stay on, check that the synthesizer and the UDB are properly
seated on the transmitter mainboard and check the following test points on the UDB. To access the
UDB, the amplifier sub-assembly and the shield lid covering the UDB will need to be removed:
Test Point
Signal Monitored
Typical Voltage
TP1
Ground
0 VDC
TP2
Logic power
+3.3 VDC ± 5 %
TP3
DSP core supply
+1.2 VDC ± 5 %
TP4
CPLD core supply
+1.8 VDC ± 5 %
Test Points are shown on the VHF / UHF Transmitter Jumper and Test Point Locator Illustrations.
If the UDB voltages are not within the specified tolerances, the transmitter mainboard (that supplies
these voltages to the UDB) is most likely faulty. If the UDB voltages are within the specified
tolerances, it is likely that the synthesizer or the UDB, or both, are faulty.
If the transmitter front panel NORM/OFF/ KEY TX switch is set from the OFF position to the NORM
position; the two front panel LEDs both turn ON for less than two seconds and then turn OFF; and the
RF output power control is set at its maximum in the “Power Levels” field of RSS Service mode, but
the RF output power is considerably less than 8.0 W:
•
Ensure that Synthesizer Reference is set to Internal in the “Jumper Settings” field of RSS Service mode.
•
Ensure that the output of the synthesizer module on the RF cable is 0 dBm (± 2 dBm) and that the RF
frequency will change with programmed channel changes in the RSS. If this is not the case, it is likely that
the synthesizer or the UDB, or both, are faulty.
** Refer to the Specification Data Sheets (located in this manual)
for the full Supply Voltage range.
