Another Ranger Restoration

by Ken - K6FC

 Several 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 had hoped!

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:


Function SW4A Position Connections SW4B Position Connections
Off (6-7-8) (7-8) (11-12)
Tune (1-2) (6-7-8-9)
Phone (1-2-3) (6-7-8-9) (1-2) (4-5) (7-8) (9-10)
Standby (1-2-4) (6-7) (9-10-11)
CW (1-2-5) (10-11-12) (3-4) (9-10) (11-12)



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:

  1. WA1HLR audio and PTT.
  2. AD5X drive pot modification.
  3. W3AM mods 1-7 except for the retention of C69.
  4. CW 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.


Other Modifications Planned From the Start

  1. 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.

  2. 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).

  3. Remove the 6146 filament interconnects (pins 7 and 8) on socket X13A.  Permanently connect the 6146 filament (pin 2) to 6.3 VAC.

  4. Remove the low voltage DC from pin 4 of X13A.

  5. Connect 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.

  6. 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.

  7. 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.

Later Issues:

  1. 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.

  2. With 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.

  3. Higher voltage on the plate of the 6146 (or some gremlin) resulted in the final breaking into occasional oscillation.  A neutralization circuit became necessary.

  4. 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.

  5. 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 close.

  6. 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.

Power Supplies

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.


Neutralization

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.


Wiring

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 installed.


Other

The tables below outline the wiring connections to the modified mode switch.

Position SW4A
1 No Change (T1 Primary)
2 No Change (AC Hot from fuse)
3 Connect to SW4A-5
4 No Connection
5 Connect to SW4A-3 & to K2A armature (115 VAC for antenna relay)
6 Connect to SW4B-7 & pin 7 of V13
7 No Connection
8 Ground
9 Connect to SW4A-10 & R12
10 Connect to SW4A-9
11 No Connection
12 Ground


Position SW4B
1 Modulator Screens via 100 ohm resistors
2 K1B  N.O. contact (Switched Low +B)
3 Ground
4 K1 & K2 coils
5 PTT switch (rear apron with microphone connector)
6 No Connection
7 Connect to SW4A-6
8 K2C N.O. contact
9 Connect to SW4B-12 & SW4X-9 & L21
10 No Connection
11 Connect to L20 & L13 & R15 junction
12 Connect to SW4B-9


Position SW4X (Added two pole – five position ceramic wafer)
1 (Wiper) Lo B+
2 Junction of 1N4007 & 7.5K 5 W resistor (Drive pot mod)
3 No Connection
4 No Connection
5 No Connection
6 No Connection
7 (Wiper) Connect to Modulation Transformer CT and phase inverter
8 No Connection
9 Connect to SW4B-9 and High B+ (L21 & new C77 junction)
10 No Connection
11 No Connection
12 No Connection



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 reasonable measure.


Mechanical/Physical

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!


Photos

Front Panel

Photo 1 - Front Panel

Photo 2 - Wafer Switch and Relays

Note the mode switch with three wafers.

The 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.

The socket space for the 5R4 accommodates the two 470 uF 450 volt HV filter caps (in series) stacked above each other.

The 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 – RF Section

The 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 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 chassis.

Photo 6 – Audio Section

The 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 zener diode.

The 12AX7 audio amplifier is located at the top center between the two tuning shafts.

The 12AU7 phase inverter socket is located towards the bottom of the photo.



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.




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22 October 2009