There appear to be three distinct Ranger models. First came the plain Ranger. The Ranger I added the keyer mod. The ranger II removes the 11 meter band and adds 6 meters. My unit is an early kit built Viking Ranger without any keying mod.
When I got the Ranger home, I noticed the power cord was frayed with bare wires visible where it entered the back panel. The seller was lucky he didn't get shocked.
I replaced the frayed cord with a modern grounded power cord. I crammed a fuse holder into the chassis corner. I would have preferred a detachable power cord but there just wasn't enough room for the connector.
Johnson used two electrolytics in series for the high voltage cap, without any equalizing resistors. The original showed signs of distress, so I replaced it. Most mods call for using equalizing resistors, but I followed Johnsons' practice and left them out.
After an on air test I decided to replace the rest of the electrolytics. Some of those were hard to remove.
The Ranger is designed to work with a crystal high impedance microphone.
I don't have one.
I do have a high impedance Shure mike that sensitive enough to drive the Ranger.
Unfortunately, the Shure also picks up hum fields from the Ranger's power transformer.
My next step was to replace the mike jack with a four conductor jack
that can supply voltage to an electret mike so I can use my hacked D104 microphone.
Trust me, you do not want to remove the top cover of the VFO. Removing it is trivial. Replacing it is NP complete because the fiber tuning rods no longer hold their springs in place. If you don't know what this is all about, you don't want to know. Trust me.
The chassis is made of aluminium.
This makes drilling holes for mods easy.
So is stripping threads by over tightening.
The case is made of steel, so I couldn't use my "hole mover over" to make room for a grounded power connector.
The Ranger had a habit of sometimes transmitting when the function switch was switched to TUNE position. Contact cleaner didn't help. Finally I used a plastic tool to apply pressure to individual contacts. The transmit mode responded to movement of one of the contacts. I applied pressure to the contact as I worked the switch to remove a bit of crud from it. The switch appears stable now.
Voila! Ranger driving a dummy load. The loading is turned way down so the bulb wouldn't saturate the picture.
I now have at least six (6) different ham transmitters, not counting handhelds. Two (Johnson Viking Ranger and FlexRadio 1500) came with no mic. What a menagerie. It may get worse before it gets better.
So I came up with CUMIC - for Chuck's Universal Microphone Connector.
When restoring the Ranger I first replaced the 2 pin round connector with a standard 3 conductor phone jack. This was not quite pleasing as the available jacks didn't fit the hole. I tried a high impedance Shure mike but it picked up hum from the magnetic fields put out by the Ranger's power transformer and/or choke.
My D104 had a bad crystal element, which I replaced with a Radio Shack electret. Of course, the electret is not a direct replacement for the crystal element. The electret requires voltage to work.
My junk box yielded two 4 pin round mike connectors used with a Kenwood tr-7400. The local electronics store (now out of business) had compatible connectors in panel mount and male cable types. I could have "standardized" on 8 pin connectors used on the Icom 756 Pro but the pins are too close together for comfort.
So I decided to use a 4 pin connector.
The chassis mount version fits in the same hole as the original 2 pin Ranger connector.
Pin 1 audio
Pin 2 PTT
Pin3 (audio) ground
Shell - possible for PTT ground (if the PTT current causes an audible ground loop)
On the Ranger, I added a cap at the mic connector so a bias voltage on the mike lead would not cause problems with the mic input stage.
I changed the bypass cap on the modulator cathodes to 1000 mf. A 2k connects to a 470 mf cap, and then to pin 4 with a 3.3k. If a suitable cathode DC voltage is not handy, rectify the 6.3 volt filament voltage instead.
This arrangement allows me to connect a high impedance mike to pin 1. The Ranger takes the high impedance signal just as it always has.
An electret mike with separate bias gets its bias voltage on pin 4. The Radio Shack electret has plenty of output, so the impedance mismatch compared to a crystal mike is not a problem with the Ranger.
An electret mike without separate bias can use 1 and 4 tied together. This would come in handy if the mike cable doesn't have enough conductors for a separate bias supply.
With simple passive adapters I can use my hacked D104 with the Icom or Flex radios.
Maybe in the future I will make an audio system fit for a radio station. Until then, CUMIC should get the job done.