The Johnson Ranger and Ranger II has been stated by a few well respected hams as the best AM transmitter made by Johnson. The Viking I is also considered excellent with the heavy duty 4D32 final amplifier and a great final amplifier tuning network. The Ranger transmitter has been modified a lot. But, per respected W8JI, it only needs one modification and that is changing the 500pF capacitor to .01uF for better low frequency response, The capacitor is from 12AX7 pin 7 to pin 1. It is located by the microphone gain control. That's it. It is so well designed no other mods are needed. Some like to solid-state the 5R4 rectifier, but the extra 50 volts is not a good idea IMO. But, no issues have occurred with the extra voltage. Some place a huge capacitor on the high voltage choke output, but an increase from 10uF to 33uF will reduce the AC ripple to about 4 volts. Lower AC ripple is not necessary. The low B+ 6AX5 rectifier is sometimes converted to solid-state, but the 450 volt capacitor will reach 600 volts during tube warm up. Use a 47uF 600 volt capacitor on the choke output with a solid-state rectifier. At 15 HY, the choke and 47uF cap results in same effect as a 700uF capacitor. 47uF is plenty of capacitance. All old electrolytic capacitors need replacement. Study the schematic located during a search on internet using johnson ranger bama. Do not forget the dual capacitor under the 12AU7 and 6AL5 mounting plate. While you are at it, a .047uF @ 250 volt cap is under that 12AU7 and 6AL5 mounting plate. My cap was a color coded bumble bee cap. I used a 400 volt replacement. Three .1uF paper caps are under the chassis by the speech amp. And, a .02uF 1600 volt capacitor is across the modulator. Although my cap measured good, I replaced it with a .02uF 2000 volt capacitor. After the new capacitors, the Johnson Ranger will work for many years with reliability. My Ranger produces 50 watts output. You will not hear much difference from a 100 watts transmitter such as the Viking I. The Viking I weights 75lbs. That requires two people to safely move. The Ranger is much more manageable at 39lbs. It has been stated the driver transformer is not adequate. That is untrue. The Ranger modulator makes en easy 100% modulation and the modulation output transformer is not small. If you have to replace the 1614 modulator tubes, they are very difficulat to find and expensive. The tubes are rated at 450 voltas plate and have 500 volts on the plates. The 6L6GB is only rated at 360 volts and vintage 6L6GC rated at 500 volts are over $100 new. Use Sovtek 6L6WXT with the stepped base or Svetlana 6L6GC. These tubes are rated at 500 volts and a new pair is about $40.
Johnson Ranger and Astaic D104 microphone Note- If using a D104 microphone, cut the 1 meg ohm resistor at the 12AX7 grid going to ground. 1 meg resistance will have about -8dB response at 100Hz. Install a new 5 meg ohm resistor from 12AX7 grid to ground for a -2dB dip at 100Hz. At the mic input jack install a .005uF capacitor in series with the mic input wire to stop the 2 volts bias from the 12AX7 grid to the mic element. The Astatic microphone will not have the best low end response with the Ranger low 1 meg input resistance.
