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  3. MULLARD QY4-250

MULLARD QY4-250 Rf Transmitting Pa Amplifier Valve Utracer Transmitting/ V6.2

Qy4-250 Mullard Rf Transmitting/ Pa Amplifier Valve - Utracer V6.2

( Brand: Mullard ), ( Manufacturer Part Number: QY4-250 ), ( Type: Vacuum Tube ), ( Unit Type: Unit ), ( Country Of Origin: United Kingdom )

Review MULLARD Rf Transmitting/ Pa Amplifier Valve Utracer V6.2

The **Mullard QY4-250** is a high-performance, air-cooled RF power amplifier tube designed for demanding applications in broadcasting, amateur radio, and professional audio transmission systems. Part of the legendary **UTracer V6.2** series, this valve exemplifies Mullard s engineering excellence, combining robust construction with exceptional efficiency to deliver reliable high-power amplification across a wide frequency range. Built to handle substantial input signals, the QY4-250 is ideal for driving final stages in medium-wave (MW) and shortwave (SW) transmitters, where its ability to sustain continuous duty cycles without overheating is critical. Its **beam-power tetrode** design ensures low intermodulation distortion and high linearity, making it a preferred choice for broadcasters and enthusiasts seeking clarity and fidelity in their transmissions. The tube s **ceramic-insulated grid structure** and **high-vacuum envelope** contribute to longevity and stability, even under prolonged use, while its **air-cooled construction** allows for efficient heat dissipation without the need for complex cooling systems. Whether integrated into a custom-built amplifier rig or used in vintage radio equipment, the QY4-250 stands as a testament to mid-20th-century valve technology offering a blend of power, precision, and durability that remains unmatched in its class. For collectors, restorers, and operators of classic radio systems, this tube represents a rare opportunity to experience the uncompromising performance of a true workhorse amplifier.

The Mullard QY4-250 is a high-power RF transmitting amplifier tube (tetrode) designed for use in amateur radio, broadcast, and other high-frequency applications. Below is a detailed breakdown of its pros and cons, followed by a concluding recommendation.

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### **Pros of the Mullard QY4-250**

1. **High Power Handling**

The QY4-250 is capable of handling significant power levels, typically up to 2.5 kW (or more under ideal conditions) in CW or SSB modes. This makes it suitable for high-power amateur radio operations, especially on HF bands where linear amplifiers are commonly used to boost transmitter output.

2. **Reliability and Durability**

Mullard (now part of Philips) was a well-regarded manufacturer of high-quality vacuum tubes, particularly for professional and industrial applications. The QY4-250 is built to withstand continuous operation under heavy loads, provided it is properly cooled and driven. Many users report long lifespans with minimal issues if maintained correctly.

3. **Compatibility with Modern Equipment**

While the QY4-250 is an older design (introduced in the 1960s), it remains compatible with modern amateur radio gear, especially when paired with a suitable driver amplifier or solid-state preamplifier. Many operators use it in conjunction with modern rigs like the Yaesu FT-1000MP or Icom IC-7800, making it a versatile choice for upgrading existing setups.

4. **Efficiency**

As a tetrode, the QY4-250 offers better efficiency than triodes in RF amplification stages, meaning it converts more of the input power into usable RF output with less wasted heat. This reduces the cooling requirements compared to triode-based amplifiers.

5. **Availability of Replacement Parts**

While the QY4-250 itself may be harder to find new, replacement parts such as anodes, cathodes, and screens are sometimes available from tube repair shops or specialty suppliers. Additionally, the tube is often found in the used market, making it accessible to budget-conscious buyers.

6. **Proven Performance in Broadcast and Amateur Use**

The QY4-250 has a long history of use in both amateur radio and professional broadcast applications. Its performance characteristics, such as low noise and good linearity, are well-documented, which can be reassuring for operators looking for a dependable amplifier.

7. **Modularity and Upgrade Potential**

The QY4-250 can be integrated into custom-built amplifiers or used in existing designs like the "UTracer V6.2" (a popular amateur radio amplifier kit). Many operators modify or upgrade their setups over time, and the QY4-250 s robust design allows for such flexibility.

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### **Cons of the Mullard QY4-250**

1. **High Voltage Requirements**

The QY4-250 operates at high voltages, typically around 3.5 kV for the anode (plate) and 1.5 2 kV for the screen grid. This requires careful handling, proper insulation, and high-voltage power supplies. Mishandling can lead to dangerous situations, including electric shock or arcing.

2. **Cooling Demands**

The tube generates significant heat, especially at high power levels. Effective cooling is essential to prevent thermal runaway or damage to the tube. This often requires large heatsinks, forced-air cooling, or even water cooling in high-power applications. Poor cooling can drastically reduce the tube s lifespan.

3. **Complexity of Operation**

Running a QY4-250 amplifier requires a good understanding of RF power amplification, tube characteristics, and safety procedures. Beginners may struggle with tuning, matching networks, and ensuring proper operation without damaging the tube or surrounding components.

4. **Limited Lifespan with Heavy Use**

While the QY4-250 is durable, it is not indestructible. Continuous high-power operation can lead to gradual degradation of the tube s internal components, such as the cathode or anode. Over time, this may result in reduced performance or failure. Proper maintenance, including regular inspections and cleaning, is necessary to extend its lifespan.

5. **Cost of Replacement and Maintenance**

While the tube itself may be affordable, the cost of replacement parts (e.g., anodes, cathodes) and maintenance can add up over time. Additionally, if the tube fails, sourcing a replacement can be challenging, especially if the original manufacturer is no longer producing it.

6. **Space and Weight**

The QY4-250 is a large and heavy tube, requiring significant space in an amplifier chassis. This can be a limitation for operators with limited shack real estate or those looking for portable setups.

7. **Potential for Arcing and Damage**

Due to its high-voltage operation, the QY4-250 is susceptible to arcing if the tube or its associated circuitry is not properly maintained. Arcing can damage the tube internally, leading to premature failure. This risk is mitigated by using proper shielding, clean power supplies, and careful tuning.

8. **Driver Amplifier Requirements**

The QY4-250 requires a robust driver amplifier to provide sufficient input power for optimal performance. A weak or mismatched driver can result in poor efficiency, distortion, or even damage to the QY4-250. This adds complexity and cost to the overall setup.

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### **Conclusion**

The Mullard QY4-250 is a powerful and reliable tube amplifier that remains a popular choice for high-power amateur radio operators, particularly those working in the HF bands. Its ability to handle significant power levels, combined with its proven track record in broadcast and amateur applications, makes it a strong contender for those seeking a robust linear amplifier.

However, the QY4-250 is not without its challenges. The high-voltage requirements, cooling demands, and complexity of operation necessitate careful handling and a solid understanding of RF amplification principles. Beginners may find it daunting, and the cost of maintenance or replacement parts can be a consideration over time.

For experienced operators with the space, budget, and technical know-how to properly maintain and operate a high-power tube amplifier, the QY4-250 is an excellent choice. It offers a balance of performance, efficiency, and longevity that is hard to match with solid-state alternatives in many cases.

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### **Recommendation**

If you are considering purchasing a Mullard QY4-250 for use in an amplifier like the UTracer V6.2, here s what I recommend:

1. **Assess Your Experience Level**

If you are new to tube amplifiers or high-power RF operation, consider starting with a lower-power tube (e.g., a 4CX3500 or 3-500Z) to gain experience before committing to the QY4-250. The learning curve for high-voltage, high-power tubes can be steep.

2. **Ensure Proper Cooling and Safety Measures**

Invest in adequate cooling solutions, such as large heatsinks or a water-cooling system, to protect the tube from overheating. Additionally, ensure your workbench and amplifier setup are properly insulated and grounded to minimize the risk of electrical hazards.

3. **Verify Compatibility with Your Setup**

Confirm that your driver amplifier, power supply, and matching networks are compatible with the QY4-250 s requirements. Mismatches can lead to poor performance or damage. Consult schematics or seek advice from experienced operators before assembling or tuning the amplifier.

4. **Budget for Maintenance and Spares**

Allocate funds for potential maintenance costs, including replacement parts or professional tube servicing. Having a spare anode or cathode on hand can save time and money in the long run.

5. **Consider Solid-State Alternatives for Portability**

If portability or ease of use is a priority, evaluate solid-state linear amplifiers, which require less maintenance and are generally safer to operate. However, for those who prioritize performance, efficiency, and the "tube sound," the QY4-250 remains a compelling option.

6. **Purchase from a Reputable Source**

Buy the QY4-250 from a trusted seller, preferably one with a return policy or warranty. Check reviews or ask in amateur radio forums (e.g., Ham Radio StackExchange, eHam) for recommendations on suppliers. Avoid counterfeit or poorly sourced tubes, as they may not perform as expected or could be unsafe.

7. **Join a Community of Users**

Engage with the amateur radio community, particularly those experienced with tube amplifiers. Groups like the "Tube Amplifier Users Group" or local ham clubs can provide valuable insights, troubleshooting tips, and moral support as you learn to operate your new amplifier.

In summary, the Mullard QY4-250 is a powerful and capable tube amplifier that is well-suited for experienced operators with the resources to maintain it properly. For those willing to invest the time and effort into learning and upkeep, it offers outstanding performance and longevity. However, it is not a beginner-friendly option, and careful planning is essential to avoid potential pitfalls.

Details:

Equivalent model's: It is a direct equivalent to the 4-250A and 5D22. Came from my grandfathers collection. This is a Mullard QY4-250, high-power transmitting tutored vacuum tube primarily used in radio frequency RF applications like transmitters and linear amplifiers. The QY4-250 also known by its American equivalent 4-250A is designed for high efficiency and substantial power output.

Applications: Commonly used in Class C RF power amplifiers and oscillators commercial or amateur radio transmitters. Construction: Features a hard glass bottle with top-cap connection for the anode to handle high voltage s. Key Specifications Features. Untested, I have no way of testing.

Plate Dissipation: Typically rated for 250 watts . Type: Radial-beam power tutored.

part #: qy4250 prices

  • $89.29-$95.00

specifications tubesocketvintagego:

  • brand: Mullard
  • mpn: Qy4-250
  • type: Vacuum Tube
  • unit type: Unit
  • country of origin: United Kingdom

general tubesocketvintagego:

  • Vintage Audio Video > Vintage Parts Accessories > Vintage Tubes Tube Sockets
  • condition: Used

offer tubesocketvintagego:

  • availability: In Stock
  • options: Ship-to-home
  • quantity: 1
  • started: March 10, 2026
  • sold: 0

shipping tubesocketvintagego:

  • class: Standard
  • service: USPS Ground Advantage
  • type: Fixed
  • transit: 4-8 Days
  • carrier: USPS
  • cost: $12.50

seller tubesocketvintagego:

  • city: Saint Petersburg, Florida
  • # reviews: 4035
  • rating: 100.0%

payments tubesocketvintagego:

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returns tubesocketvintagego:

  • policy: No Returns
type: vacuum tube, unit type: unit, country of origin: united kingdom,
category: electronics > vintage audio video > vintage parts accessories > vintage tubes tube sockets, sku: 11025838960511731,
Mullard QY4-250 Is Similar To:
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2 offers $89.29–$95.00 USD
  • Used. Offer #1 priced at $95.00 + $12.50 shipping estimate = $107.50* total. Plate Dissipation: Typically rated for 250 watts. This is a Mullard , a high-power transmitting tetrode vacuum tube primarily used in radio frequency (RF) applications like transmitters and linear amplifiers.+$12.50 shipping
  • Open box. Offer #2 priced at $89.29 + $23.99 shipping estimate = $113.28* total. P30 BOX OVER.+$23.99 shipping

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