Codan Radio Communications UT-4E900 Manuel D’Utilisation

MT-4E VHF & UHF Receiver & Transmitter Instruction Manual

IM08-MT-4E-TXRX-P1162

VHF & UHF Hardware Tuning and Troubleshooting

transmitter Mainboard

Check the following test points on the transmitter mainboard:

TP1

Voltage from Motherboard +13.8 VDC Line

+13.8 VDC**

TP2

Regulated +9.5 VDC from Motherboard

+9.5 VDC ± 5 %

TP3

USB Connector Power

+3.0 VDC or +5.0 VDC

TP4

Switched +13.8 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:

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.