These are still among the best FM exciters ever made, the Broadcast Electronics FX Series.
This one just needs a little clean up, new capacitors, a new fan and an unused accessory card removed.
This one has an accessory that I haven’t seen too often, a synchronized booster card. This Exciter was at one point used in that service. We’ll remove that card as it isn’t needed. Doing so requires you replace U1, a decade counter, on the PLL/AFC board.
Looks like the fan was replaced about 11 years ago. It’s not unusual to get 15 years or more out of these Papst fans, they’re very well built. We’ll replace it as part of our refresh.
Power supply regulator and control board before the caps are replaced.
Brand new main PS cap. Amazing how much smaller they are than just a decade ago. The unused stud is one of the mounting screws from the original capacitor. It was that much larger.
Oscillator/PLL board. All the capacitors here have been replaced. Often the dip switches used to select the operating frequency need replacement too. These are still operating correctly so we’ll leave them alone.
Nichicon makes capacitor lines specifically for audio use. “muse” for bipolar and “gold” for traditional polarized use. We’ll use those as appropriate in audio circuits.
Here’s the FMO- frequency modulated oscillator. It is responsible for converting audio into FM. Unlike AM which varies carrier amplitude with audio, FM varies carrier frequency. BE originally potted these things in a goop that’s impossible to remove. They stopped that practice in later production. The two power supply filters are bulged at the bottom, one is leaking.
Here are the Nichicon gold capacitors installed. Board cleaned up underneath the caps, still some damage underneath one of them where a leak had started.
All the pieces reassembled into a clean chassis. I haven’t seen one of these yet that still has the alignment tool in place. Also note the shipping screws are reinstalled into the FMO. They need to be removed in use to get the audio noise level down.
And off she goes, making 51 watts into a dummy load with full modulation. It will burn in this way at least 24 hours. Then we’ll check it out on the Belar monitors and ship it out.
These exciters are generally trouble free with a near bulletproof RF section. They should provide excellent service for at least another decade.