Shahriar from the SignalPath purchased a defective Agilent E4433B ESG-D Signal Generator as a teardown and repair project. Sounds expensive but this piece of equipment is an expensive piece of gear. Shahriar goes through the troubleshooting of the system in great detail and repairs the fault!
“The Output RF board is equipped with various amplifiers, electronic attenuators, I/Q mixers, heterodyne paths and final PA. By using soldered SMA cables to various points in the signal path, the fault is traced to an internal amplifier chain which is likely made of a MESFET or JFET transistor. Since this part is obsolete, an RFMD GaAs hybrid amplifier is used in its place. The biasing network and matching networks need to be modified to accommodate this change. The repaired unit is then verified for functionality and performance by measuring a QAM constellation output signal.”