Ken - K6FC
years ago at the Hosstraders Hamfest I picked up a Johnson
Ranger. I had wanted one to restore and although this one was
no beauty contest winner, it came home with me.
Move ahead to winter 2008-2009 and it was time to get started as cold
weather had set in and outside activities were limited. I
gathered up as much information as I could find on the Internet and
started the task. Kudos to WA1HLR, AD5X, W3AM, and K4XL for
their fine articles on Ranger modifications. Their write-ups
covered a major part of the effort. A download of the Ranger
manual from BAMA completed the necessary documentation.
Like most tasks of this sort, one makes changes: some due to parts
availability and some the result of a “better mousetrap”
determination. My goal was to get the Ranger operational
again and if possible add to the body of work already available.
My first task was to open up the Johnson and get an idea of what lay
ahead. After removing the cabinet it was obvious there was
going to be a lot of cleaning involved. To say it was filthy
was an understatement and the original soldering job (was it a kit?)
was not exactly mil-spec! Plastic insulated solid wire was
used – a lot of that had to go! In addition the Johnson PTT
modification had been made and that process had butchered the wiring
around the mode switch. This was not going to be as easy as I
I removed the front panel knobs and then the front panel. All
the knobs came off with only a little effort (better than a rust bucket
Viking II I restored several years ago). With the panel off
it was obvious a decent cleaning job was going to require some
disassembly and that began with the mode switch which had attracted a
lot of “grunge” and chunks of solder. I thought to myself
this was going to complicate things later in the rewiring process – but
it had to be done. After removal and thorough cleaning (I
used “Bar Keepers Friend” and a toothbrush) it looked almost
new. But how did all those contacts and wipers work
together? The following table is the result of a visual and
ohmmeter study of the two switch wafers:
||SW4A Position Connections
||SW4B Position Connections
(4-5) (7-8) (9-10)
At this point some serious rewiring was going to be required and I had
to decide what principal features I wanted to incorporate.
This was my list:
audio and PTT.
- AD5X drive
- W3AM mods
1-7 except for the retention of C69.
operation like an unmodified Ranger.
These requirements were not quite compatible with the mode switch
connections and try as I might I couldn’t do everything I wanted:
specifically to have HV on the modulator only in the phone position and
to get 6146 grid drive in the tune position. Looking at the
switch it was apparent there was enough length available to add a
wafer. Checking the junk box I found a two-pole five-position
ceramic wafer that would work as long as I used some shorter spacers
between the wafers. This addition can be seen in Photos 2 and 3
and serves the two functions noted above. Actual wiring of
the new SW4 is described later in the text.
Modifications Planned From the Start
- Get rid of
the J5 crystal socket (115 VAC for antenna relay) and install a small
Jones two prong receptacle. It is my “standard” for powering
an antenna relay.
- 12 VDC
supply for powering relays (5 VAC 5R4 winding in series with 6.3 VAC
winding to a half wave rectifier and filter capacitor).
- Remove the
6146 filament interconnects (pins 7 and 8) on socket X13A.
Permanently connect the 6146 filament (pin 2) to 6.3 VAC.
- Remove the
low voltage DC from pin 4 of X13A.
switched 12 VDC (from new PTT relay) to pin 4 of X-13A. Now
an external relay can be keyed such as the one found in a 51J4.
- Connect a
grounded PTT relay contact (opens when transmitting) to pin 8 of
X-13A. Thus one can mute a receiver such as a 75A4.
- R3 is
removed from the VFO box and the 0A2 removed and replaced with a 160
volt 10 watt zener diode mounted on the main chassis away from the VFO.
- Check all
resistors: many of the originals were far out of specification and had
to be replaced, especially the SH series. C89, a paper
capacitor in the keyer, must be replaced.
silicon rectifiers and 235 uF of filtering, the high voltage in standby
rose above 900. 60K of bleeder was added to bring the voltage
down to 800+ volts.
voltage on the plate of the 6146 (or some gremlin) resulted in the
final breaking into occasional oscillation. A neutralization
circuit became necessary.
- The plastic
insulation protecting the high B+ wires (bare) going through the X13A
shield was pretty well shot and arced at 900 VDC. With 235 uF
of filtering one gets a good arc! The old plastic was
replaced with two concentric Teflon sleeves.
- During the
incident noted above, SH4, the shunt resistor for monitoring plate
current went POW! Had the meter selector switch been in the
plate position, no doubt the meter would have been toast.
Recognizing that arcs can occasionally occur, the replacement SH4 was
installed in the cathode of the 6146 so that the meter is out of the HV
circuit. The plate current reading will be off slightly as
the meter now reads plate, screen and control grid currents – but it’s
- The WA1HLR
design for the 6AQ5 clamper/6146 screen puts full HV (via R15) on the
6AQ5 plate in standby. I wasn’t sure how well the 6AQ5 would
like 800+ volts, so I decided to connect the clamper plate to the 5K
6146 screen resistor and have the PTT relay switch that point from
ground on standby to HV on transmit.
All rectifier tubes were replaced by silicon. The HV filter
capacitor, C77, was replaced by two 470 uF 450 volt caps in series
(with 470K equalization resistors) for a total of 235 uF. The
LV filter capacitor, C78, was replaced by a single 470 uF 450 volt
unit. The bias filter capacitor, C90, was replaced with a 100
uF 150 volt cap. The modulator bias source is identical to
that shown in the W3AM article.
A typical ARRL Handbook circuit was used here. L12 was
replaced by a 2.5 mH RF choke and C36 (.005 uF) was replaced by two
silver micas (620 pF above the chassis and 330 pF below). A
glass piston trimmer from the 6146 plate to the bottom of L6A through
an insulated feed-thru completes the circuit. Photos 4 and 5
show the details of this addition.
A lot of the original wiring was simply removed as the plastic
insulation in many cases had melt spots due to excessive application of
the soldering iron or dropped solder. In the high voltage
circuits 1000 volt insulated wire was used. The original AC
power cord was tossed and a modern three wire grounded polarized cord
The tables below outline the wiring connections to the modified mode
Change (T1 Primary)
Change (AC Hot from fuse)
to SW4A-3 & to K2A armature (115 VAC for antenna relay)
to SW4B-7 & pin 7 of V13
to SW4A-10 & R12
Screens via 100 ohm resistors
N.O. contact (Switched Low +B)
& K2 coils
switch (rear apron with microphone connector)
to SW4B-12 & SW4X-9 & L21
to L20 & L13 & R15 junction
||SW4X (Added two pole – five
position ceramic wafer)
of 1N4007 & 7.5K 5 W resistor (Drive pot mod)
Connect to Modulation Transformer CT and phase inverter
to SW4B-9 and High B+ (L21 & new C77 junction)
The schematic diagram (thanks to TinyCad) shows the
modifications made to the 6146 PA and 6AQ5 clamp tube circuits as well
as the connections to the two transmit relays. The 1N4007
diode allows the multiplier tube, V4, to be active in the tune mode
(this allows PA grid current tuning) while isolating other circuits
that require low B+ only during transmit.
With the move of resistor SH4 to the cathode of the 6146, the meter
switch wiring will change and that is noted in the schematic
diagram. While this change was made primarily to protect the
meter, getting the high B+ off the meter switch seemed like a
The Ranger came with only one of the three long screws that secure the
cabinet to the transmitter chassis. Substitutes were made
using 10-24 “all-thread” with nuts silver soldered at one end of the
all-thread to tighten things up (note: flat washers should be used
between the nut and chassis).
The knobs and front panel were carefully cleaned with mild soap to
remove dirt and tobacco smoke residue and then lightly buffed after a
light application of furniture polish.
The cabinet paint was heavily scratched. The paint was
removed by glass bead blasting and then primed and repainted
gray. Not a close match to the front panel color, but it
doesn’t look bad!
Photo 1 -
2 - Wafer Switch and Relays
mode switch with three wafers.
socket for the 6AX5 is now used for a 2PDT relay. The 4PDT
miniature relay is located just behind this relay where the old Johnson
PTT relay was located.
socket space for the 5R4 accommodates the two 470 uF 450 volt HV filter
caps (in series) stacked above each other.
modulator bias supply is incorporated onto the underside of the keyer
shelf and the bias adjusting potentiometer has been located in the 6AL5
socket hole using a centering washer and two larger washers above and
below the aluminum plate.
Photo 3 –
Underside of keyer showing bias supply
Photo 4 –
neutralization capacitor (a 2-14 pF glass piston trimmer) is soldered
to a two lug terminal strip and located on the rear shield between the
6146 and the tank coil. A screw hole (the original screw was
one of two for attaching the bracket supporting the tank switching
wafer) was enlarged to ¼ inch to accommodate an insulated feed-thru for
connection to the underside circuitry.
To the right of the 6146 there are the two 10 watt resistors in series
that constitute the high voltage bleeder.
Photo 5 –
Neutralizing and VFO Mods
The neutralization feed-thru is shown on the bottom of the chassis
where is comes through the wafer support bracket. A “nibbler”
was used to remove a small portion of the multiplier circuit shield so
that the neutralizing wire could directly enter the shielded area and
complete the neutralizing circuit.
Note the 160-volt zener diode for regulating the VFO that is located
toward the bottom center of the photo. An 8.5K 10 watt
dropping resistor for the zener is positioned on the inside wall of the
Photo 6 –
470 uF 450 volt low voltage filter capacitor, located behind the audio
gain potentiometer, occupies the space formally held by T3, the
modulator driver transformer.
Below this capacitor is an 8.5K voltage dropping resistor for the VFO
The 12AX7 audio amplifier is located at the top center between the two
The 12AU7 phase inverter socket is located towards the bottom of the
Photo 7 – Power Supplies and Wiring
The LV and HV rectifiers are encased in heat shrink tubing and mounted just to the right of LP2, the low voltage choke.
The 12 VDC supply is shown just above LP2.
The drive potentiometer modification resistors are shown in the upper left corner of the photo.
The rewiring effort used colored and numbered wires.
22 October 2009