1. Why Are TT Welwyn Customers Looking for Alternatives?

TT Electronics' Welwyn brand holds a prominent position in European industrial and medical equipment BOMs. The HVP planar radial series is a staple for compact high-voltage modules, while the axial families (T43/T44/T48, F series, and CGH) are foundational for X-ray equipment, analytical instruments, and high-frequency HV power supplies.

However, relying solely on a single major European supplier in today's supply chain landscape presents significant challenges:

• Obsolescence (EOL) Risks: Several legacy series, such as the F series (F43/F44) and the precision CGH series, have been officially marked as obsolete. Although the manufacturer recommends migrating to the T series, this forces OEMs to re-evaluate dimensions and electrical performance anyway.
• Lead Time Uncertainty: High-voltage sub-assemblies operate on strict schedules. Extended delivery windows for standard components or custom ohmic values severely impact both mass production and aftermarket maintenance.
• Cost Reduction Pressures: Securing a reliable second source that offers identical form-factor and electrical parameters at a competitive price is a critical strategy for lowering overall BOM costs.
• Dual-Sourcing Strategy: For medical devices and precision instruments, component shortages can lead to exorbitant re-certification costs. Implementing a seamlessly switchable alternative model early in the design phase is an industry best practice.

HVC specializes in high-voltage thick film resistor technology, utilizing a mature process of 96% Al₂O₃ ceramic substrates + Ruthenium Oxide (RuO₂) paste + high-temperature firing. With product lines covering both planar radial and axial cylindrical formats, HVC provides precise 1:1 cross-referencing against Welwyn's key specifications.

2. Planar Radial Series: TT HVP → HVC HVR-GHP Cross Reference

The TT Welwyn HVP series features compact, planar high-voltage resistors known for low inductance and capacitance, often competing directly with the EBG FSX series. HVC's direct equivalent is the HVR-GHP series. The table below meticulously aligns with TT's official HVP.pdf datasheet, offering a dimensionally identical drop-in replacement.

Selection Note: The "HVC Direct Replacement" column indicates the base shell code. A complete orderable part number requires the resistance value and tolerance. For example, to replace TT's HVP06C-100MF (100 MΩ, 1%), the standard HVC format is HVR-GHP1/2-100MF. Note: If the TT model specifies the powder-coated option, add 0.25mm to the L, H, and T dimensions.

3. Axial Cylindrical/Tube Series: TT T40 Family → HVC HVR-BOP / BSP Cross Reference

For applications demanding higher power dissipation and extreme voltage ratings, TT promotes the T40 Series (including T43, T44, T48), which are ceramic tube axial thick film resistors. The core logic for replacing cylindrical resistors is: Prioritize matching the body diameter (D) and length (L) while ensuring power and voltage requirements are met. HVC addresses these needs with the BOP (slim tube), BSP (standard robust tube), and PFS (high-power ultra-HV custom) series.

Dimension Note: The TT lengths cited below correspond to the "D" style (standard axial wire terminals). If the original part utilizes KU (one wire, one screw) or TU (dual screw) terminations, the total physical length will slightly increase. HVC offers custom terminations to match these specific requirements.

Replacements for Obsolete Axial Series

HVC continues to provide long-term, stable drop-in replacements for obsolete TT series frequently found in legacy BOMs:

• F Series (F43 / F44): Typically 0.7W to 1.3W, max 14kV, with ohmic values up to 100GΩ. Easily replaced by selecting the closest length-to-diameter ratio from HVC's HVR-BOP or HVR-BSP lines.
• CGH Series (1/4W to 5W): Precision high-voltage axials up to 20kV, supporting tight 0.5% tolerances and low 50ppm TCR. Flawlessly substituted by HVC's high-precision/low-TCR HVR-BSP variants.
• CMH Series: MIL-R-49462 approved parts. HVC can supply high-voltage components that meet equivalent electrical testing and reliability standards.

4. Integrated High-Voltage Dividers: TT HVD / RHVD → HVC 100% Custom Engineering

The TT HVD (Single-In-Line) / RHVD (Dual-In-Line) series are voltage dividers that integrate a high-voltage resistor (R1) and a low-voltage resistor (R2) into a single module, providing exceptional ratio accuracy and TCR tracking. Because these products are highly customized to the OEM's mounting pitch and specific ratio requirements, their original part numbers are exceptionally complex (including R1 value, R2 value, absolute tolerance, and ratio tolerance).

Common Outlines and Electrical Specs for HVD Series:

HVC's 100% Custom Replacement Solution: Due to the specialized nature of dividers, HVC does not rely on rigid "shell-to-shell" catalog swaps. Instead, we offer a 100% custom engineering and communication service. By utilizing identical batches of thick film paste and simultaneous firing processes, we guarantee ultra-low ratio drift. Customers simply provide the complete TT Welwyn part number (e.g., H30CD-100M/100KFD), the required voltage ratio, pin spacing, and operating medium (air/oil/epoxy potting). The HVC engineering team will then match and issue custom packaging drawings that fully meet or even exceed the original tracking precision.

5. How to Quickly Obtain Samples and Quotes

HVC's replacement methodology is built on robust engineering data and extensive field cross-referencing experience. Whether you are specifying for a new project or urgently mitigating lead-time and obsolescence issues on an existing build, simply provide us with:

1. The complete TT Welwyn part number (e.g., HVP15D-100MF or T44D-10MJI)
2. The operating medium (Air, Transformer Oil, SF6 gas, or Epoxy potting)
3. Any special pulse handling or precision requirements

Our engineering team will provide a detailed technical comparison datasheet and a sample delivery schedule within 48 hours.

Copyright: © HVC Capacitor. No reproduction or commercial use without permission.
Disclaimer: Technical specifications are compiled from the latest available manufacturer datasheets. TT, Welwyn, TT Electronics, and HVP are registered trademarks or product names of their respective owners. They are referenced herein strictly for objective technical compatibility and cross-reference purposes.