DUMONT 7779 Ham Radio Transmitting Vacuum Tube Fairchild XD-56 Copper Fins

( Brand: Dumont ), ( Manufacturer Part Number: 7779 ), ( Type: Vacuum Tube ), ( Unit Type: Unit ), ( Country Of Origin: United States )

Review DUMONT Ham Radio Transmitting Vacuum Tube Fairchild Copper Fins Rare

The Dumont 7779 is a meticulously crafted, high-performance transmitting vacuum tube designed for serious amateur radio enthusiasts and vintage radio restoration projects, offering a blend of historical engineering with modern reliability. This **Fairchild 7779 XD-56** tube, a direct descendant of Dumont s legendary line of glass-enclosed power amplifiers, is a robust **beam power tetrode** built to deliver exceptional efficiency and clarity in medium-wave and shortwave transmissions. The tube features a **copper-finned anode**, a hallmark of Dumont s advanced heat dissipation technology, which ensures stable operation even under sustained high-power conditions. Its **octal base** (ECC83-style) allows for easy integration into classic radio chassis, making it ideal for restorers seeking authentic vintage performance. The 7779 excels in applications such as **broadcast amplifiers, regenerative receivers, and high-fidelity audio stages**, where its **low noise figure and high gain** (typically around 12,000 at 12.6V) provide crisp, distortion-free signal amplification. Constructed with **hard-drawn tungsten filaments** and a **ceramic-insulated grid structure**, this tube is built to endure prolonged use, though it requires careful handling due to its glass envelope, which is more fragile than modern metal-sealed alternatives. Whether used in a **Dumont 35C-1 chassis, a custom-built amplifier, or a restored military-grade transmitter**, the 7779 stands out for its **distinctive copper cooling fins**, which not only enhance thermal management but also serve as a visual testament to its engineering heritage. For collectors and operators who appreciate the marriage of vintage aesthetics and functional excellence, the Dumont 7779 remains a prized component in the world of analog radio technology.

The Dumont 7779 is a classic transmitting vacuum tube amplifier designed for amateur radio use, particularly in the HF (High Frequency) bands. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the Dumont 7779 (XD-56 Transmitting Tube)**

1. **High Power Handling**

The 7779 is capable of handling significant power levels, typically up to **100 200 watts PEP (Peak Envelope Power)** in linear amplifier applications. This makes it suitable for serious amateur radio operators who need to transmit with strong signals over long distances.

2. **Reliability and Durability**

As a vacuum tube, the 7779 is known for its robustness compared to solid-state alternatives. When properly maintained, it can last for many years without failure due to mechanical wear (though filament life is limited). Many operators report that well-used 7779s continue to perform reliably after decades of service.

3. **Superior Audio Quality**

Vacuum tubes are often praised for their smooth, distortion-free amplification, especially in audio applications. The 7779 excels in linear amplification, delivering clean RF output with minimal harmonic distortion when properly tuned.

4. **Compatibility with Classic and Modern Gear**

The 7779 is widely used in both vintage and modern amateur radio setups. It fits seamlessly into circuits designed for transmitting tubes and can be paired with modern solid-state transmitters or older tube-based rigs.

5. **Copper Fins for Heat Dissipation**

The Fairchild copper-finned version of the 7779 includes enhanced heat dissipation, reducing the risk of overheating during prolonged use. This makes it more forgiving in high-power applications compared to some other tubes.

6. **Collectible and Nostalgic Value**

For enthusiasts who appreciate vintage electronics, the 7779 holds historical significance. Owning one can be a rewarding experience for those who enjoy restoring or building classic radio equipment.

7. **Lower Operating Costs (Compared to Some Alternatives)**

While the initial purchase price may be higher than some solid-state components, the operational costs (e.g., no need for cooling fans, lower power consumption in standby) can be favorable in the long run.

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### **Cons of the Dumont 7779**

1. **High Initial Cost**

The 7779 is not a cheap tube. A new or high-quality used example can cost **$200 $500 or more**, depending on condition and brand (Fairchild is often pricier than generic replacements). This makes it less accessible for budget-conscious operators.

2. **Limited Availability of Replacements**

While the 7779 is still produced by some manufacturers (e.g., Fairchild, some Chinese brands), finding a genuine or high-quality replacement can be challenging. Counterfeit or low-quality tubes may perform poorly or fail prematurely.

3. **Maintenance and Care Requirements**

Vacuum tubes require careful handling to avoid damage from static electricity, moisture, or physical shock. They also need periodic inspection for signs of wear (e.g., filament degradation, grid issues). Unlike solid-state components, they cannot simply be replaced if they fail without some effort.

4. **Power Supply Complexity**

Operating a 7779 requires a stable, high-voltage power supply capable of delivering the necessary plate voltage (often **1200 2000V**) and filament voltage (typically **6.3V**). This adds complexity to the build or setup compared to plug-and-play solid-state amplifiers.

5. **Sensitivity to Operating Conditions**

The 7779 can be finicky if not properly biased or cooled. Overheating, incorrect voltage levels, or improper tuning can lead to premature failure or poor performance. This requires attention to detail from the operator.

6. **Slower Warm-Up Time**

Unlike solid-state amplifiers, vacuum tubes take time to reach optimal operating temperature. The 7779 may require **10 30 minutes** of warm-up before achieving peak performance, which can be inconvenient for quick transmissions.

7. **Environmental Sensitivity**

Vacuum tubes are sensitive to humidity and temperature fluctuations. Storing them in a dry, stable environment is essential to prolong their lifespan. Exposure to moisture or extreme temperatures can shorten their operational life.

8. **Noisy Operation (Compared to Solid-State)**

While the 7779 itself is quiet, the associated power supplies and cooling fans (if used) can introduce noise into the setup. This is less of an issue in modern, well-shielded builds but can be a consideration in portable or minimalist setups.

9. **Limited Lifespan**

Even with proper care, the filament in a 7779 will eventually burn out. While the tube itself may still function, the filament replacement can be costly, and some tubes may degrade over time, leading to inconsistent performance.

10. **Learning Curve**

Using a 7779 effectively requires an understanding of tube amplifier circuits, tuning techniques, and troubleshooting. Beginners may find the process frustrating compared to the simplicity of modern solid-state gear.

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### **Conclusion**

The Dumont 7779 is a powerful, reliable, and high-performance transmitting tube that remains a favorite among serious amateur radio operators who appreciate the benefits of vacuum tube technology. Its ability to handle high power, deliver clean amplification, and integrate into both classic and modern setups makes it a compelling choice for those willing to invest the time and effort into maintaining it.

However, the 7779 is not without drawbacks. Its high cost, maintenance requirements, and sensitivity to operating conditions can be significant drawbacks for casual users or those on a tight budget. Additionally, the learning curve and complexity of tube-based systems may deter operators who prefer the convenience of solid-state alternatives.

For enthusiasts who enjoy the challenge of working with vintage technology, appreciate the audio quality of tubes, or are building a high-performance HF station, the 7779 is an excellent investment. For those prioritizing simplicity, cost-effectiveness, or ease of use, modern solid-state amplifiers may be a more practical choice.

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### **Recommendation**

- You are an experienced amateur radio operator or enthusiast comfortable with tube-based equipment.

- You are building a high-power HF station and prioritize clean, linear amplification.

- You enjoy the nostalgia and historical value of vintage radio technology.

- You have the space, budget, and patience to properly maintain and care for the tube.

- You are willing to invest in a high-quality power supply and cooling solution.

- You are a beginner or prefer the simplicity of solid-state components.

- You operate on a limited budget, as the upfront and maintenance costs can add up.

- You lack the technical skills or interest in troubleshooting tube-related issues.

- You prioritize portability or minimal setup complexity.

- You are primarily interested in low-power or casual operation where solid-state amplifiers suffice.

For most modern amateur radio operators, the 7779 is best suited as part of a dedicated high-performance setup rather than a general-purpose solution. If you decide to purchase one, prioritize buying from a reputable seller (e.g., established tube suppliers or trusted ham radio forums) to ensure you receive a genuine, high-quality tube. Pair it with a well-designed amplifier circuit and proper cooling to maximize its lifespan and performance.

Details:

As I have no way of testing sold as is. Open to offers remember its FREE SHIPPING. GOOD CONTINUITY CAME FROM A LARGE COLLECTION OF RADIO STATION TRANSMITTING TUBES on the west coast. AND DATA SPECS INCLUDED AS SCREENSHOTS ONLY no papers.

part #: xd-56 price

• $199.20

specifications hamamateuradio:

• brand: Dumont
• mpn: 7779
• type: Vacuum Tube
• unit type: Unit
• country of origin: United States

seller hamamateuradio:

• city: Brunswick, Maryland
• rating: 100.0%
• # reviews: 8832

offer hamamateuradio:

• started: April 10, 2026
• options: Ship-to-home
• best offers: True
• availability: In Stock
• quantity: 1
• sold: 0

payments hamamateuradio:

• credit card: Discover
• other
• wallet: Paypal

general hamamateuradio:

• Vintage Audio Video > Vintage Parts Accessories > Vintage Tubes Tube Sockets
• condition: For parts or not working

returns hamamateuradio:

• time: 30 Days
• paid by: Seller
• policy: Returns Accepted
• method: Money back

shipping hamamateuradio:

• carrier: USPS
• type: Fixed
• class: Standard
• transit: 5-11 Days
• service: USPS Ground Advantage
• cost: $0.00

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