0.9GHz 500mW Video Transmitter Repair

Recently I got a 0.9GHz 500mW video transmitter for repair. The owner just connected power reverse polarized and the transmitter went up in smoke. 🙄

I took the transmitter apart and after a quick voltage check I found the voltage regulator to be defective.

Just replaced the 78M08 linear voltage regulator on the lower side of the PCB, the part circled in red.

Took also some quick RF measurements to check the transmitter:

DIP1 DIP2 TX Frequency RF Power
0 0 1040 MHz 27,0dBm
0 1 1010 MHz 27,2dBm
1 0 980 MHz 27,3dBm
1 1 910 MHz 27,5dBm

 

 

 

 

RF Harmonics for 910MHz, 27.44dBm TX:

1280MHz = -20.6 dBc
2730MHz = -14.8 dBc

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