Equivalent & Substitute Parts for Ohmite 810F40R

Part Overview

The Ohmite 810F40R is a 40 Ohms ±1% 10W wirewound chassis mount resistor from the Metal-Mite®89 series. This component is classified as obsolete, making direct sourcing increasingly difficult. Identifying qualified substitute parts ensures design continuity and maintains supply chain reliability for applications requiring this resistance value and power rating specification.

Substiute Parts

810F40R

OhmiteIn Stock: 1112810F40R Datasheet

Current PartRFQ

UAL25-40RF8

RiedonIn Stock: 978UAL25-40RF8 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the Ohmite 810F40R is based on the following critical parameters:

• Electrical Match: Resistance value (40 Ohms) and tolerance (±1%) must be identical
• Power Capability: Substitute must meet or exceed the 10W power rating
• Thermal Characteristics: Temperature coefficient (±20ppm/°C) and operating range (-55°C to 275°C) must be maintained
• Mechanical Compatibility: Wirewound composition, aluminum housing, flange mounting, and solder lug termination are required for form-fit-function equivalence

The Riedon UAL25-40RF8 qualifies as a direct substitute by meeting all electrical and mechanical parameters while providing enhanced power handling (25W) and active product status.

Parameter Comparison

Engineering Selection Recommendations

The Riedon UAL25-40RF8 is the qualified substitute for the Ohmite 810F40R based on the following factors:

• Electrical Equivalence: Identical resistance (40 Ohms) and tolerance (±1%) ensure direct functional replacement
• Thermal Performance: Matching temperature coefficient and operating range maintain circuit performance across environmental conditions
• Power Margin: The 25W rating provides operational headroom beyond the original 10W specification
• Active Status: The substitute is in active production, ensuring long-term availability and supply chain stability
• Compliance: ROHS3 compliance of the substitute addresses modern regulatory requirements, whereas the original part is non-compliant

Physical dimensions differ slightly (UAL25-40RF8 is larger), requiring verification of board layout and thermal management provisions in the application.

Frequently Asked Questions (FAQ)

Q: Can the Riedon UAL25-40RF8 be used as a direct replacement for the Ohmite 810F40R?

A: Yes. Both components share identical electrical specifications (40 Ohms ±1%, ±20ppm/°C temperature coefficient, -55°C to 275°C operating range) and mechanical features (wirewound, aluminum housing, flange mount, solder lugs). The substitute's higher power rating (25W vs. 10W) is compatible with applications designed for the original 10W part.

Q: What are the physical differences between these parts?

A: The Riedon UAL25-40RF8 is larger than the Ohmite 810F40R. The substitute measures 1.063" L x 1.079" W x 0.575" H (max), compared to the original's 0.750" L x 0.812" W x 0.400" H (max). Board layout and thermal clearance must be verified before implementation.

Q: Does the substitute meet current compliance standards?

A: The Riedon UAL25-40RF8 is ROHS3 compliant, whereas the Ohmite 810F40R is non-compliant. This makes the substitute suitable for applications subject to modern regulatory requirements.

Q: Are there any electrical performance differences?

A: No. Both parts maintain identical resistance tolerance (±1%) and temperature coefficient (±20ppm/°C). The substitute's higher power rating does not affect electrical performance in circuits designed for 10W operation.

Q: What is the packaging difference?

A: The Ohmite 810F40R is supplied in box packaging, while the Riedon UAL25-40RF8 is supplied in bulk packaging. This affects inventory management and handling procedures but does not impact component functionality.