The Johnson Viking Ranger
by Greg Latta, AA8V

Restoration

 
Transformers Before Painting
Transformers Before Airbrushing - January 14, 2014
Click on the image for a larger view.
Click here for a super detailed view.

 
Transformers After Painting
Transformers After Airbrushing - May 28, 2014
Click on the image for a larger view.
Click here for a super detailed view.

Johnson Viking Ranger Pages:
 Johnson Viking Ranger - Main Page and Exterior Photos  Alignment
 Interior Photos of the Transmitter  Modifications
 Restoration  Schematic Diagrams and Circuit Descriptions
 Typical Operating Conditions  Manuals and Advertisements

Important Safety Note: Working on or testing equipment such as the Viking Ranger is extremely dangerous since very high voltages are present when the equipment is turned on, and may even be present when the equipment is turned off and unplugged. If at all possible, do all work with the equipment off and unpluggedand be sure that the capacitors are properly discharged before working on the equipment. The operator assumes all risk and liability in such matters! Do not work on this type of equipment unless you are experienced with working around very high voltages!

Restoration:

Scroll Down or Select A Link Below:
 Introduction
 Initial Cleaning
 Tube Testing
 Testing The Power Transformer
 Testing The Filament Circuits
 Testing The B+ And Bias Circuits
 Ordering Replacement Parts
 Drive Control Replacement and Initial RF Output Test
 Power Supply Rebuilding And Replacement Of R35
 Line Cord And Fuse Holder Installation
 Speech Amplifier Capacitor Replacement
 Modulator Testing
 VFO Repair And Cleaning
 Chassis Cleaning
 Front Panel Cleaning
 Knob Cleaning And Indicator Insert Replacement
 Frequency Scale Cleaning And Painting
 Rubber Seal For The Escutcheon
 Transformer Airbrushing
 Cabinet Restoration
 Final Speech Amplifier Repair

Introduction:
On the evening of November 1st, 2013 I was on the 80m band with my 2E26/813 transmitter and I wound up working W3PH, Paul Heller, in Deep Creek Lake, MD. During the QSO I mentioned to Paul that I did a lot of building with vacuum tubes. Paul then mentioned that he had a Johnson Viking Ranger transmitter that he was willing to give me for free if I wanted it. He had purchased it at a hamfest some 30 years ago with the intention of restoring it, but had never gotten to it. It had been sitting in a plastic bag in his shed all those years. After a couple of e-mails Paul brought the Ranger to my house two days later, and on November 3rd, 2013 I was the proud owner of a rather sorry looking Viking Ranger. It was in terrible shape and full of sawdust and mouse droppings, but the mice had simply moved in and hadn't eaten any of the rig. With a lot of work it looked like it could be cleaned up and put back on the air.

After six months of painstaking restoration work the transmitter went back on the air Wednesday, June 11th, 2014. I made the first QSO with crystal control and then switched to VFO control from my external digital VFO. I now have the Ranger on the air on a regular basis. It sounds great, looks great, and was well worth all of the time I spent working on it.

Initial Cleaning:
As received the transmitter was very dirty and certain areas were full of mouse droppings and sawdust. A thorough vacuuming with the shop vac and a chip brush cleaned everything out. First inspection showed that the mice had simply moved in and had not eaten anything. No frayed wires or other such damage was found, and there was no corrosion on the chassis, just the usual dirt that would be expected after almost 60 years.

Tube Testing:
The tubes were removed, making note of which particular socket each 6CL6 and 12AU7 was in. Noting the particular tube socket guarantees that each tube goes back into the same socket, since alignment sometimes depends on the particular tube, and there are two 6CL6 and 12AU7 tubes in the Ranger.

The tubes were tested in an Eico dynamic tube tester, and some were found to be weak. These were replaced with tubes that I already had in stock. The 6AX5GT rectifier showed some heater to cathode leakage, but it was high enough that it would not cause any problems. The 6146 final amplifier tube tested OK, but the only real way to test an RF amplifier tube is by actually using it, and that would have to wait until later.

Testing The Power Transformer:
The power transformer is one part in a transmitter that is not easy to replace. If the transformer is defective, then there is not much point in restoring the transmitter, so testing the transformer was the first order of business after testing the tubes.

The worst thing one can do is to plug in the transmitter and turn it on, hoping for the best. This is a sure road to disaster. The transformer or filter capacitors could be shorted, leading to at best a blown fuse and at worst a fire. Instead, thorough checks should first be made with an ohmmeter to check for shorts and other problems before the transmitter is even plugged in. Filter capacitors should be checked for shorts, and also with a capacitor tester if possible to see if they have the correct capacitance.

After thorough checks with an ohmmeter, all tubes were removed. In the case of the Ranger, removing the rectifier tubes also disconnected the transformer secondary from the rest of the B+ circuits, allowing me to independently check the transformer and transformer primary circuit.

The transmitter was plugged into a VARIAC (variable AC source) and a voltmeter was placed across the high voltage secondary. The VARIAC was set for 10% (about 12V), and the transmitter was turned on. The voltage on the high voltage secondary was observed to be 10% of the expected value. The other secondaries were also checked, and all showed 10% of the expected value. The VARIAC was slowly increased to 25%, 50%, 75% and finally 100% with checks on the secondary voltages each time to confirm proper operation. No other problems were observed. The transformer appeared to be OK.

Checking The Filament Circuits:
After the power transformer was tested, all tubes except the rectifier tubes were plugged into their sockets and the transmitter was turned on. All of the tube filaments should have lit up, but quite a few did not. After checking the schematic and the manual it was found that unless the 9-pin accessory plug was plugged in, some of the tubes were disconnected from the filament supply. Inserting the accessory plug cured the problem and all of the tubes lit up, confirming proper operation of the filament circuits.

Testing The B+ and Bias Circuits
To test the B+ and bias circuits, all of the tubes except the rectifiers (5R4, 6AX5, and 6AL5) were removed. The filter capacitors in the high B+ (C77) low B+ (C78) and bias (C90A and C90B) circuits were tested with an ohmmeter and capacitor tester and found to be OK. A jumble of resistors used to replace R35 was also removed. The line voltage was then brought up slowly on the VARIAC while the output of these supplies was tested. All seemed to produce full output when the VARIAC was brought all the way up, and no overheating was observed anywhere in the transmitter.

However, there was a problem in the the plate current meter indicated plate current even though no other tubes were in the transmitter. This was initially a concern, but it turns out that this is normal. The final amplifier/clamper tube circuit is wired so that R15, the 30kohm screen dropping resistor, will draw current through the plate current meter even when the clamper tube and final tube are not installed. Thus, the power supplies, and all of the power supply distribution circuits throughout the transmitter, were OK.

Ordering Replacement Parts:
With the power supplies working properly, it sure looked like the Ranger would ride again! There was still a long way to go though. The transmitter was filthy, and there were still other parts that were obviously defective, such as the drive control, R13, which was burned out, and R35, the modulator screen dropping resistor, which was totally missing.

It turns out that parts such as these are still available, and they aren't that expensive. However, shipping costs can be a substantial, and the way to minimize shipping costs is to order all of the parts you will need or MIGHT need at the SAME time. It is cheaper in the long run to order a part you might need and not use it than to have to order it later, and pay additional shipping costs. If the part isn't used, it just goes into your parts stock for future use.

In addition to R13 and R35, I also wanted to replace all of the electrolytic capacitors, including those in the power supplies. (The power supply electrolytics, though not original, and still good, were at least 30 years old.) I also planned to replace any paper capacitors (such as those in the audio section) with modern ones.

Using the parts list in the manual, I came up with a list of parts that I would need. For electrolytics in the audio section, I wanted to keep the values the same so that the audio response would not be affected. For the power supply electrolytics, moderately larger capacitors could be used. The high B+ filter capacitor C77 was a 10uf/700V unit. Such capacitors are no longer available. Instead, two 33uf/450V units were placed in series with 270kohm/3W film resistors across each one to equalize the voltage to give the equivalent of a 16.5uf/900V filter capacitor. (Note: Never use carbon resistors for equalizing resistors! Their negative temperature coefficient makes them unstable.)

When shopping for parts, remember that larger power values for potentiometers such as R13 (25kohm/4W) are perfectly acceptable. When the Ranger was made, 4W potentiometers were standard. My favorite parts supplier, Mouser Electronics, did have a 25kohm/4W potentiometer available. The trouble was that it was special order only and would cost $66!! It turns out that 5W potentiometers are now standard, and a 25kohm/5W unit was available for only $3.61!

For those who may need to replace R13, here is the part number that I used:
Mouser Part Number: 774-026TB32R253B1A1

For R35, which is a 20kohm/50W tapped wirewound power resistor I ordered the following:
Mouser Part Number: 588-D50K20KE

You will also need two of the following mounting brackets for R35:
Mouser Part Number: 588-9E

Other parts that might be hard to find that I ordered from Mouser Electronics included the following:

3 Conductor Line Cord:
Mouser Part Number: 562-311007-01

#51 Pilot Lamps:
Mouser Part Number: 560-51

Drive Control Replacement And Initial RF Test:
With replacement parts on hand, the first thing I did was to replace R13, the drive control, which controls the screen voltage on the V4, the 6CL6 buffer/multiplier, and was the last part that needed replacement before I could check the transmitter for actual RF output. Replacement was fairly straightforward. Some of the wires to the control were quite short, but I was just able to make them reach.

Once a new drive control was installed, I reinstalled all of the tubes, set the band switch to 40m, and placed my Sangean portable shortwave receiver (in CW mode) next to the transmitter. With the transmitter in tune up mode and the meter switch set to read grid current, I keyed the transmitter and checked to see if I could hear the VFO signal in the receiver. No signal was heard and no grid current was observed, regardless of where I tuned the transmitter. This meant that either the VFO wasn't working or that it was way out of alignment. The VFO was going to need some work.

I switched to crystal control, and after inserting a 40m crystal into the crystal socket I immediately heard the signal on my receiver and observed grid current. The buffer control and drive controls worked just as they should, and the signal was very clean and chirp free. I switched to 20m and 15m and still had plenty of grid current. The crystal oscillator and buffer stages were working fine.

After connecting a dummy load and Bird wattmeter to the output of the transmitter, I switched to CW mode and tried tuning up the transmitter. I got plenty of output and the final, auxiliary coupling, and coupling controls all worked exactly as expected. Maximum output was about 50W, which was exactly what it should be. The final amplifier tube and associated circuits all seemed to be in great shape. The signal sounded clean and the keying was chirp free. The Ranger was coming back to life!

Power Supply Rebuilding And Replacement Of R35:
With the RF sections working (except for the VFO) I turned my attention to the power supply filter capacitors C77, C78, C90A/B, and R35, the modulator screen dropping resistor.

Though C77 and C78 had already been replaced and were fine, they were still 30 years old, and I thought it best to replace them with modern units. C77 was originally a 10uf/700V capacitor. This was replaced with two 33uf/450V capacitors in series to give an equivalent capacitance of 16.5uf at 900V. Each capacitor was shunted with a 270kohm/3W film type equalizing resistors as shown in the photo below:

Plate Filter Capacitors
Two 33uf/450V capacitors shunted by 270kohm/3W
equalizing resistors were used to replace C77.
Click on the image for a larger view.
Click here for a super detailed view.

C78 was originally a 30uf/450V capacitor. It was replaced with a 47uf/450V unit. Capacitors C90A and C90B in the keyer/bias supply were originally a two section 15uf/50V capacitor with both sections wired in parallel. This unit had dried out and was replaced with a single 30uf/150V capacitor.

R35 was a bit of a problem because it was completely missing from the transmitter and had been replaced with an arrangement of fixed resistors. I had already removed these, but had no idea how R35 was supposed to be mounted. However, I found a copy of the assembly manual on-line and this showed where R35 should be mounted. I was amazed that, even after almost 60 years, my replacement resistor was exactly the same size as the original, and fit beautifully into the original mounting holes! You can see the new resistor in the photo below:

Resistor R35
Resistor R35
Click here for details on adjusting R35

The tap on the resistor was initially set about half way down. This would give an initial screen voltage of about 250V maximum on the 6L6GC modulator screen grids. Final adjustment would be made later. Click here for details on adjusting R35.

Line Cord And Fuse Holder Installation:
The Ranger was made at a time when power cords were not grounded. The fuses were placed in a special plug at the end of the line cord. Modern safety codes dictate that a grounded 3 conductor line cord should be used on the Ranger. I had cords in my junk box, but they were large and heavy. Since I was already ordering other parts from Mouser Electronics, I just added a new line cord to the order. The cord was 6' 7" long with 18/3 wire. The Mouser part number is below:

3 Conductor Line Cord:
Mouser Part Number: 562-311007-01

I had a large number of cord strain reliefs in stock and found one that would fit the the cord and the hole in the Ranger. The cord went in easily, but figuring out where to put the fuse was another matter. The back panel layout of the Ranger didn't permit the use of a a standard single hole mount fuse holder. Instead, I had to use a molded base fuse block. I had one in stock,but Mouser Electronics has them with this stock number:

Single fuse holder:
Mouser Part Number: 534-3536

This could be squeezed in right next to the accessory socket by drilling a single hole through the panel. Be very careful when drilling the hole not to damage anything! I used a 5A slow-blow fuse. See the photo below.

Power Entry and Exit
A molded base fuse holder can be squeezed in on the back panel as seen at top center in this photo.
Click on the image for a larger view.
Click here for a super detailed view.

Speech Amplifier Capacitor Replacement:
There are two double section electrolytic capacitors in the speech amplifier, C50A/B and C59A/B. These had both dried out and had no capacitance. Though it is OK to use larger capacitance in the power supply, using larger capacitances in the audio section could alter the frequency response. C50A/B and C59A/B were therefore replaced with new capacitors having the same capacitance. C50A/B was replaced with two 10uf/50V units, and C59A/B was replaced with two 15uf/150V units. (150V capacitors were used for C59A/B because they were much cheaper.)

Speech Amplifier
Speech Amplifier
Click on the image for a larger view.
Click here for a super detailed view.

In the photo above, C50B is the blue capacitor barely visible to the left of the red postage stamp capacitor at top, and C59A and C59B are the silver capacitors near the bottom of the photo, between the two octal tube sockets.

Though I had purchased replacement capacitors for the green paper capacitors visible in the photo, these were tested with a capacitor tester and were and found to be good. Since they were moulded in plastic, it was unlikely that they had deteriorated, so they were left alone. The new capacitors I had purchased went into my stock to be used elsewhere in the future.

Modulator Testing:
With all of the capacitors in the modulator in good shape, I installed Svetlana 6L6GC modulator tubes, and decided to test the modulator. I wanted to measure its output at flat topping and also its frequency response. The modulator drives the final amplifier through the modulation transformer, T2. The output of this transformer is available at the accessory socket X13A on the back of the transmitter. However, a suitable load must be connected to the transformer for testing.

The modulator was tested without the 6146 final amplifier tube installed, and thus without the final amplifier drawing any plate current. This yields a higher plate voltage on the modulator tubes than during actual use, but still can still provide meaningful results. The modulator must, however, be tested with the key down, since this affects the bias on the modulator tubes. As to R35, my initial adjustment was pretty near the mark, because it gave a modulator resting current of 72mA during keydown conditions in phone mode. This was very close to the 75mA minimum specified by the instruction manual so I did not, at this time, readjust R35.

The impedance that the modulator drives is the final amplifier plate voltage divided by the final amplifier plate current. According to the transmitter manual, the final amplifier should be loaded to 130mA of plate current in phone mode. At that plate current, the plate voltage would be 500V and the modulator impedance would be 500V / 0.13A=3850ohms. I had a collection of large 10W-35W wirewound resistors in my shop, and wired several of these in series and in parallel to produce a 3750ohm resistor, which is within 3% of the required 3850ohms.

The 3750ohm resistor was connected across the entire secondary of the modulation transformer at X13A, the accessory socket, and an oscilloscope was connected across the resistor. A 1kHz sine wave was then injected into the mic input. The audio gain control was increased until clipping was observed on the scope, which occurred at 430V RMS, corresponding to an output of (430V)*430V)/3750ohm=49.3W. The output was reduced to 200V RMS (10.7W output) and the frequency was varied above and below 1kHz to find the -6dB frequencies where the output voltage dropped to 100V RMS, half of its value at 1kHz. The frequencies where the output was 6dB lower than at 1kHz were found to be 110Hz and 3500Hz.

To properly modulate the 6146 final, 65W/2=32.5W would be needed from the modulator. Even under real operating conditions, with the final amplifier operating and with lower plate voltage, the modulator could clearly meet that requirement. The frequency response of the amplifier was also found to be very good. Assuming a good microphone, the Ranger should sound great on the air!

VFO Repair And Cleaning:
Initial testing had shown that the VFO was not working, though no problems could be seen when the lid to the VFO cabinet was removed. To access the rest of the VFO, the VFO cabinet was carefully removed and two problems were immediately found:

1. Mice had also moved into the VFO cabinet and the entire area was a mess.
2. The original VFO regulator dropping resistor R3 had burned out and had been replaced with a new resistor, one end of which was held in place with an alligator clip! Evidently, whoever did the repair couldn't reach that end of the resistor with a soldering iron, so they used an alligator clip. Not exactly a stable repair, but you have to give them credit for ingenuity!

The mouse bedding was cleaned out and the entire VFO area was thoroughly cleaned. As elsewhere in the transmitter, the mice had only moved in, and had not eaten any wires. The chassis and all components inside the VFO cage were cleaned with Q-tips and lighter fluid (naptha) and then waxed with Q-tips and Pledge furniture polish to prevent dust from adhering in the future.

Resistor R3 and the alligator clip were removed and replaced with a new 3W film resistor. This wasn't easy, since things were very tight, even with the VFO cabinet removed. (The original repairer probably didn't remove the VFO cabinet, which would have made soldering one end of R3 impossible. That's probably why they used the alligator clip.)

After replacing R3, the VFO came to life. The frequency was not stable, and jumped around a bit. All connections inside the VFO cabinet were resoldered, but the instability remained. Most likely, the fixed capacitors had become unstable over the years, and would have to be replaced to settle down the VFO. Since I planned to use an external VFO anyway, I left the original capacitors in place, and reinstalled the VFO cabinet.

Chassis Cleaning:
With most of the electrical restoration done, it was time to worry about the cosmetic appearance of the Ranger. The chassis, front panel, knobs, and cabinet were all in need of work, and I decided to tackle the chassis first.

My standard procedure is to first clean as much of the chassis as possible with a very small rag or piece of paper towel and Ronsonol lighter fluid (naptha). Over the years I have found that lighter fluid is relatively benign and does a great job of cutting through grease and other deep grime. (If you are in doubt as to whether to use the lighter fluid on a surface, test a small inconspicuous area first.) After as much as possible is done with the rag, I then switch to using Q-tips and lighter fluid. I mount my Q-tips in a special brass handle that I made to hold them, as shown in the photo below:

Q-tip Holder
Brass Holder For Q-tips.
Click on the image for a larger view.

The handle is made of brass and has a hole drilled in one end that provides a snug fit for the Q-tip. The Q-tips are cut off with a pair of side cutting pliers and then inserted into the end of the handle, as shown in the photo. The handle allows me to get into all of the tight places on the chassis that cannot otherwise be reached. You can control the flex of the Q-tip by how much of the shaft you leave on the Q-tip. I usually cut my Q-tips in half, and do a whole bunch at once to save time.

To use the Q-tip, put some lighter fluid on it. If you get it too wet, touch it to a small rag or piece of paper towel to remove the excess. When the Q-tip gets dirty, take it out and insert another. You go through a lot of Q-tips, and it is much like cleaning the floor of your kitchen with a toothbrush, but you can get to all of those tight places and get them all clean.

I even clean the components (variable capacitors, especially the steatite/ceramic insulation, fixed capacitors, resistors, and coils (after carefully testing on a small part of the coil)) this way as well. Yep, the process is time consuming, but it is about the only way to really get the chassis clean.

After everything is cleaned with lighter fluid, the entire process is repeated using Pledge furniture polish to resist dust build-up and give everything a nice shine.

Finally, after the top of the chassis is done, the entire process is repeated with the bottom side.

It takes a lot of time, but in the end it is worth it, as can be seen in the photos.

Front Panel Cleaning
To clean the front panel, the knobs and the front bezel were removed. The panel and bezel were then cleaned with a small damp paper tower pad covered with clear coat auto polishing compound. This compound contains the finest abrasive available, and is normally used to polish the clear top coat applied to automobiles. It will polish and clean panels without affecting silk screened or painted makings. Carefully polishing the front panel removed the patina on the panel and made the silk screen markings stand out very nicely. It also gave the front panel a glossy finish. After cleaning the panel with the clear coat polishing compound, a damp pad with only water on it was used to remove all traces of the compound, and then Pledge furniture polish was used to wax the panel. Though the front panel has some nicks in it, these give it some character, and were left untreated. The rest of the panel looks new, as can be seen in the photo below:

{short description of image}
Front Panel After Restoration
Click on the image for a larger view.
Click here for a super detailed view.

Knob Cleaning And Indicator Insert Replacement
The knobs were cleaned by first removing the set screws, and then the white indicator inserts were removed from them with a pair of needle nose pliers. (Many of these were already missing). The knobs were then scrubbed down with water and a toothbrush soaked with Soft Scrub kitchen cleaner. The soft scrub does an excellent job of removing years of patina from the knobs, and the toothbrush gets into the nooks and crannies of the knobs leaving them very clean. The knobs were then sprayed and polished with Pledge furniture polish, which puts the shine back on the knobs.

New white indicator inserts were made from 1/4" white acetal plastic rod I had on hand. The acetal was turned down to a diameter of exactly 1/8", with a length slightly longer than necessary. The end of the insert was beveled very slightly in the lathe. The beveled end was then inserted into the knob and snipped off with side cutting pliers, which leave the cut end a little out of round and oval shaped. The insert was then removed, turned around, and the out of round cut end was pressed into the hole, the oval shape providing the friction needed to keep the insert in place. Some extra inserts were also made to keep in stock in case any were lost in the future. A restored knob is shown in the photo below:

Restored Knob
Restored Knob
Click on the image for a larger view.

Frequency Scale Restoration:
The front bezel was removed from the front of the transmitter and then the plexiglass frequency scale was carefully removed from the bezel. The bezel was treated the same as the front panel. It was cleaned and polished with clear coat auto polishing compound and then waxed with Pledge furniture polish. Though there were some nicks in the finish, these were left in place, since they gave the bezel some character.

The transmitter frequency scale posed a real problem. Aside from the usual scratches and gouges in the plexiglas, a semi-circle had been cut out of the middle of the scale, leaving an ugly rough edge on the inside of the scale, and some of the major frequency markings were covered with blotches of some sort of clear glue (super-glue?) All of these problems can be seen in the left photo below.

The real problem was how to remove the blotches of glue. I eventually found by careful testing that if I rubbed the blotches with Q-tips dipped in lighter fluid and then very carefully scraped them with my fingernail, I could slowly wear away the the blotches, without scratching the plexiglas or harming the silk screened markings on the scale. It took a while, but I was eventually able to remove all of the markings. Both sides of the scale were then carefully polished with with clear coat auto polishing compound and then waxed with Pledge furniture polish. After the polishing and waxing the scale had most of its original shine and contrast.

The inside edge of the scale, where the semi-circle had been cut out, was cleaned and painted with flat black enamel. This kept light from leaking out of the inner edge and made it almost invisible against the front panel. If you didn't know it beforehand, you might not notice that the inner part of the scale was missing. The final results can be seen in the photo below on the right. Luck was really with me on this one!

 
Unrestored Bezel
Unrestored Bezel And Frequency Scale - December 29, 2014
Click on the image for a larger view.

 
Restored Bezel
Restored Bezel and Frequency Scale - June 6, 2014
Click on the image for a larger view.

Rubber Seal For The Escutcheon:
On some Rangers the rubber seal behind the front escutcheon has rotted and split. According to Steve Stroschein, W9XF, the following item, available from Amazon.com, fits like a glove:
Universal U Channel Rubber Seal Strip 1/32" Opening Edge Trim All Weather Protector Strip (5ft)

Escutcheon Seal
Click here or on the image for a larger view.

Click here to order from Amazon

Transformer Airbrushing:
After the knobs, front panel, bezel, and chassis had been restored, the Ranger was looking really great. Besides the cabinet, the only cosmetic problems left were the high voltage power supply choke LP1 (which looks like a large transformer) and power transformer T1. These were very rusty (especially the laminations), as can be seen in the photo at left below. They had so many connecting wires (or the wiring was so tight) that removing them from the chassis was not an option. I could perhaps paint them with a brush, but that would leave brush marks, and there were areas I could not get to with a brush. I finally decided that if I thoroughly masked off the entire chassis I could airbrush the transformers. Airbrushing would allow me to spray paint down into the nooks and crannies and get them completely painted, without any brush marks.

As you can imagine, masking off every area of the chassis except for the transformers was a big job. Masking off the area between LP1 and T1 (where the 6146 tube and tank coil are located) was particularly difficult. I used newspaper and lots of Scotch blue masking tape. I had to cover the components, but keep the masking away from the transformers so I could spray their sides. It took several hours, but after the masking was finished I put the chassis on a large lazy susan and airbrushed the transformers first with a coat of Rustoleum Professional rusty metal primer (7569), and then with several coats of gloss black Rustoleum (High Performance Protective Enamel V7579). The airbrush allowed me to paint every surface of the transformers, even the sides and backs. After letting the paint dry for a couple of days, I put all of the tubes in the transmitter and turned it on standby, letting the heat gently bake the paint. The results were worth all of the work, as you can see in the photo at right below:

 
Transformers Before Painting
Transformers Before Airbrushing - January 14, 2014
Click on the image for a larger view.
Click here for a super detailed view.

 
Transformers After Painting
Transformers After Airbrushing - May 28, 2014
Click on the image for a larger view.
Click here for a super detailed view.

Cabinet Restoration:
As received the cabinet was in terrible shape. It had been spray painted with some kind of dark blue paint that was chipping and flaking off, and there were scratches all over the cabinet. It was apparent that a complete paint job was needed.

Savogran Strypeeze paint stripper was applied to the cabinet and it was stripped down to the bare metal. Steel wool was then used to remove the last traces of paint and to thoroughly clean the base metal. The cabinet was then washed and dried.

There was no hope of duplicating the original cabinet color (I wasn't even sure what it was supposed to be!), so I decided to paint the cabinet a shade of grey that matched the front panel. This was obtained by mixing 2 parts gloss black Rustoleum (High Performance Protective Enamel V7579) to 1 part gloss white Rustoleum (High Performance Protective Enamel V7592). The cabinet was first airbrushed with a couple of coats of Rustoleum Professional rusty metal primer (7569), and then airbrushed with several coats of the final grey. Some of the rubber feet were missing from the cabinet. I went down to our local music/sound equipment store and purchased a nice set of feet normally used for a large guitar amplifier. These fit the cabinet perfectly. The final result was better than I ever expected, as can be seen in the photos below:

Ranger Rear
Cabinet After Restoration
Click on the image for a larger view.
Click here for a super detailed view.

Final Speech Amplifier Repair:
The transmitter went back on the air June 11th, 2014. I made several CW contacts, first with crystal control, and then with my digital VFO. I used the transmitter on CW for about a week and a half and got excellent signal reports. Satisfied the RF circuits were working correctly, I decided to take the plunge and operate on AM. However, after fitting a microphone to the transmitter and testing it into a dummy load, I discovered I had intermittent audio. I had a devil of a time tracking down the problem, because the transmitter worked fine with the cabinet off, but would malfunction with the cabinet on! Finally, after getting it to malfunction with the cabinet on, I very carefully edged it out of the cabinet a little at a time until I could very carefully insert a couple of test sockets into the speech amplifier tube sockets. These allowed me to make voltage measurements from the top side of the chassis. Measurements finally showed that coupling capacitor C52 (500pf) in the speech amplifier was leaking and causing the second section of the 12AX7 preamplifier,V7B, to saturate. The leakage resistance of C52 was so high (over 20Mohms) that it could not even be read on an ohmmeter! Replacing the capacitor, however, cured the problem. I had my first AM QSO with the Ranger on June 22nd, 2014. (My first AM QSO ever in 46 years as a ham!) Initial reports were that the audio sounded great. The Ranger was riding the airwaves again!


meterBack to Dr. Greg Latta's Electrical Engineering and Amateur Radio Pages


Questions, Comments, and E-Mail

LetterIf you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta@frostburg.edu

Thanks for stopping by!