Still, he proudly displayed his Heathkit Mohican Receiver on his dresser in my parents bedroom. This receiver was perched on my dad's dresser from the time of my early childhood until his death several years ago, when it came into my possession.
The last time I remember the Heathkit Mohican Receiver worked was when Ronald Reagan was still president!
As a tribute to my father, I spent a month restoring his Heathkit Mohican GC-1A Receiver to a condition close to when it was originally built in 1965.
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I consult this book often during radio restoration. I grew up in the transistor and diode era and this book taught me a lot about vacuum tube and selium rectifier technology.
Heathkit Mohican Manual Download
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Amazon has a great selection of electrolytic capacitor kits, perfect for the electronic hobbyist!
XP-2 AC Power Supply Recap
The XP-2 AC Power Supply is installed in the back of the Mohican Receiver. It is held in place by two snap fittings. Use the pull ring and pull it straight back. Disconnect the internal power supply cable. Remove the rectangular aluminum cover.
The old nasty electrolytic capacitors.
The replacement electrolytic capacitors installed. Notice they are much smaller in physical size than the originals.
The nasty old yellowed original AC cord.
The new replacement AC cord installed.
Look at the cool way I attached the .1Mfd capacitors between the Input and Ground and Output and Ground pins. These capacitors will prevent the 7812 from oscillating during high loads.
After the electrolytic capacitor replacement, the output voltage shot up to 15 Volts DC. I installed a 7812 Voltage Regulator to keep the Voltage at around 12 Volts. Do NOT secure the regulator tab to the metal base. Remember, positive ground.
Below is a schematic containing my modification to the XP-2 Power Supply.
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Don't just sit on the sidelines listening to Amateur Radio broadcasts, become an active participant! This book contains all you need to pass the Technicians Exam. I studied the book, took the practice tests that came with it, and passed the exam the very first time. Most Amateur Radio Clubs sponsor the testing and conduct it at a public place like a local library.
Time to remove the metal cabinet from the chassis so that you can get at the electronics!
Remove the antenna by unscrewing and pulling up and out.
Remove the two screws from the back for the receiver on the lower right-hand side.
Remove the two screws from the back for the receiver on the lower left-hand side then slide the chassis forward until you can access the speaker.
Remove the four nuts that hold the internal speaker to the top of the cabinet. The chassis is now free and clear of the cabinet.
Bottom view of the chassis.
Cleaning and Lubrication
The Mohican Receiver's chassis has not seen the light of day since the 1980s when my dad tried to re-align the RF and IF amplifier sections. It had many layers of dust and dirt inside.
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Most radio restorations require the use of contact cleaner to remove years of oxidation from switch contacts.
Look at all the dust and dirt on the IF Board!
The rest of the chassis had a layer of dust and dirt on it as well.
I used an air compressor to blow all of the dust and dirt off of the chassis. Damp Q-Tips helped clean the less accessible areas of the chassis and IF Board.
I used electrical contact cleaner to clean all the potentiometers connected to the front panel. I would spray the cleaner into the small cutout by the terminals then work the potentiometer back and forth through its full motion.
The dial lights did not work even though my ohmmeter indicated that the bulb filaments were still intact.
Corrosion in the dial light bulb sockets prevented the light bulbs from making good contact.
The dial lights worked once again after I cleaned the bulb sockets with a Q-Tip dipped in denatured alcohol.
I used Labelle 107 Oil to lubricate all rotating parts including the shafts of potentiometers and variable capacitors. This oil will not harm plastic parts.
I used Labelle 106 Grease to lubricate the gearing connected to the Main Tuning and Band Spread capacitors. This grease will not harm plastic parts.
I used a touch of Super Glue to secure the Main tuning dial pointer to the dial string. The pointer was loose and would not track properly along the dial.
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I use Labelle oil and grease for my radio restoration projects. I already have these products around as I am also a model railroad enthusiast. These products will not harm plastic.
As mentioned, "recap" is the replacement of old electrolytic capacitors in vintage equipment. Electrolytic capacitors have a finite lifetime. As they age the electrolyte dries up causing their capacitance to fall in value. This section describes the replacement of electrolytic capacitors in the Mohican receiver.
C56, C57, and C58 are all housed in the same case. Each has a value of 100Mfd with 15Volt Max Rating.
Triple capacitors are hard to find these days. I replaced C56, C57, and C58 with three discrete electrolytic capacitors of the same rating.
The next capacitor to be replaced was C59. It has a value of 50Mfd and a 15Volt Max Rating.
I replaced C59 with a 47Mfd electrolytic capacitor with a 15Volt Max Rating. Most capacitors have capacitance tolerance of 20%, so this value is close enough.
C55 is a wax covered capacitor rated 150Mfd at 15Volt Max Voltage Rating.
I replaced C55 with a 100Mfd and a 47Mfd electrolytic capacitors in parallel, which combines for a total of 147Mfd capacitance. This is close enough to the original value.
C27 is a 10Mfd capacitor with a 10Volt Max Rating.
C27 was replaced with a new electrolytic capacitor of spec similar to the original one.
C54 is located on the underside of the printed circuit board and is connected to a terminal strip. It has a value of 50Mfd with a 15Volt Max Rating.
I replaced C54 with a 47Mfd electrolytic capacitor with the same voltage rating.
Volume Control Repair
For some reason the 5K Potentiometer used as the volume control suddenly froze. I could not turn it.
Access to the volume potentiometer can be achieved from the underside of the chassis. Remove the knob then the nut that attaches it to the front panel. It takes some finessing to get it out so that you can unsolder it.
Turns out the spring that contacts the resistive material somehow got folded over causing the extreme increase in turning resistance. Once repaired, I did a continuity check to make sure the potentiometer was functioning properly.
The process of soldering all of the wires back on the volume control potentiometer was a daunting task as the wires are very short. With some patience, you will be able to solder all wires to the proper terminals of the potentiometer.
It is important to go through the Receiver Alignment procedures in the Heath Kit Assembly manual in order to get peak performance out of your Mohican Receiver.
I would definitely recommend going through the Receiver Alignment procedures if you were not the original builder of the Mohican Receiver as kit builders range in all skill levels. A lot of kit builders may have never went through the Receiver Alignment procedures, as they may not have had access to an rf Generator, which is required for the alignment process.
I would recommend going through the Receiver Alignment process even if you were the builder of the Mohican Receiver. It is possible that the receiver could have gotten out of alignment after 50 years as components slightly change value due to age.
IF Amplifier Alignment
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Believe it or not, you can still find TV Alignment tools to purchase. These tools are rarely needed these days with Digital TV receivers and SDR (Software Defined Radio) but were once a must for any serious electronic technician.
Dial Pointer Adjustment
Band Alignment - Initial Setup
Band Alignment - Process
Time to see the fruits of my "Band Alignment" labor and connect the Mohican receiver to my G5RV external antenna. I was amazed at all the stations I was picking up of each band!
Years of tobacco smoke have taken their toll on the Mohican's enclosure. You can't just wipe the tar off, it is embedded in the paint.
Even the aluminum carry handle has a brown hue due to tobacco tar.
Be very careful what you use to clean the Mohican's enclosure! I used a mild polish that was no more abrasive than toothepaste and it left these strange watermarks. Still the watermarks beat the brown tar coating that originally coated the enclosure.
Another picture of the strange watermarks that appeared after I lightly polished the enclosure.
I used motorcycle chrome polish and an old toothbrush to clean the Mohican receiver's knobs, antenna, and handle.
Look how pretty the knobs and antenna look after polishing!
Mohican Receiver Assembly
My dad's newly restored Mohican Receiver in action!
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Who Writes This Blog?
John is an IT professional from Cleveland, OH who enjoys amateur radio, ham radio, metal detecting,
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