Whistler TRX-2 Front-End Damage Repair, Schematic Needed

[pyeman99]

The cause has been found. The second transistor in the RF amplifier, Q7, was damaged. Its electrical characteristics had degraded, although it looked perfect externally.

The original part was a BFP193 in an SOT-143 package. There is one interesting detail: it was installed upside down at the factory. This suggests that the PCB was either designed for a different transistor or that an error was made in the footprint pinout.

The factory-installed BFP193 was not a genuine Siemens/Infineon component, but a Chinese part from Alibaba. There were no signs of rework, resoldering, or flux removal, so this was clearly the original factory configuration.

Brilliant work Alex working without a circuit diagram is a nightmare. We dig deep into our skills.
Why companies are so secretive beats me,especially when those companies offer very little or no repair service,they really don't enhance their reputation.

 

[AlexCA]

Brilliant work Alex working without a circuit diagram is a nightmare. We dig deep into our skills.
Why companies are so secretive beats me,especially when those companies offer very little or no repair service,they really don't enhance their reputation.

This wasn’t my own hands-on work. I coordinated the engineers and managed the process. I have two excellent engineers available to me, both in their 40s and fully up to date with modern technology. One specializes in ground-up development, digital communications, and P25/DMR terminals, while the other specializes in microwave engineering and precision soldering. The first resolved 80% of the problems, and the second handled the remaining 20%. They simply have different areas of expertise that complement each other.