Bext LEX25. These are simple, workhorse exciters. 0-25 watts, VSWR foldback, basic remote control and metering capabilities. They are fairly good sounding units for their age and design price.
This one is 2001 vintage and has no AFC lock.
It is not helpful when they arrive like this. Chassis dented, front panel broken loose, internal components broken loose and bouncing around. It was packed pretty well. Go FedEx.
A few hours replacing capacitors, cleaning up the internals, re-securing the PC boards and the chassis panels.
This Unit has a FM Receiver board added, likely used as a Translator. You can see it in the center of the chassis.
The AFC consists of a 10Mhz crystal divided down to 10Khz and compared to the VCO, generating an error signal. That is used to keep the VCO centered and to create an AFC Lock, which then applies power to the RF sections.
The Frequency synthesizer chip (MC145191) had proper signals going in, but not out. This is an obsolete chip and becoming difficult to find, but not impossible. After replacement the exciter locked right up.
Here is the FM receiver board. It can be set to any FM broadcast frequency by changing the DIP switches. It has Main and SCA outputs, any of which can be routed to the Exciter input through a rear panel BNC jumper. The Signal Strength indication is brought out to the front panel as an aid to adjusting the receive antenna.
Simple power supply creates plus/minus 12Vdc and 5Vdc. It can be powered by 120V mains, or an external 24V supply. Those gold caps measure just a fraction of their nominal capacitance. They look fine but bad ones often do. They were replaced along with the others.
A quick check into the test set and 24 hours burn-in on the dummy load and it’s ready to return to service.