F40J2K5 Wirewound Chassis Mount Resistor – Equivalent & Substitute Parts

Part Overview

The F40J2K5 is a 40-watt wirewound chassis mount resistor manufactured by Ohmite, part of the Stackohm® 250 series. This component is rated for 2.5 kOhms at ±5% tolerance and is designed for high-power applications requiring reliable thermal dissipation. The part is currently active in production with 1,026 units in stock. Substitute parts may be required due to inventory constraints, application power derating, or compliance requirements specific to end-use environments.

Substiute Parts

F40J2K5

OhmiteIn Stock: 1116F40J2K5 Datasheet

Current PartRFQ

F30J2K5E

OhmiteIn Stock: 760F30J2K5E Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

The F30J2K5E qualifies as a parametric equivalent to the F40J2K5 based on the following criteria:

• Identical resistance value: 2.5 kOhms
• Identical tolerance: ±5%
• Identical composition: Wirewound
• Identical temperature coefficient: ±260 ppm/°C
• Identical coating and housing type: Vitreous Enamel Coated
• Identical mounting feature: Flange Braces, Right Angle
• Identical lead style: Solder Lugs
• Identical package type: Radial, Flat Oval

The primary difference is the power rating: F30J2K5E is rated at 30W versus the 40W rating of F40J2K5. This substitution is valid only in applications where the thermal load does not exceed 30 watts. The F30J2K5E also features an extended operating temperature range of –55°C to 350°C and is RoHS3 compliant, whereas the F40J2K5 is non-compliant.

Parameter Comparison

Engineering Selection Recommendations

The F30J2K5E is a valid substitute for the F40J2K5 in applications where power dissipation does not exceed 30 watts. Both parts are active products from the same manufacturer and series, ensuring design continuity and mechanical compatibility.

Selection between these parts should be based on:

1. Power Requirement: If the circuit dissipates more than 30 watts across the resistor, the F40J2K5 is required. If dissipation is 30 watts or less, the F30J2K5E is acceptable.

2. Compliance Requirements: The F30J2K5E is RoHS3 compliant, making it suitable for applications subject to RoHS regulations. The F40J2K5 is non-compliant and should be used only where RoHS exemptions apply.

3. Temperature Range: Both parts operate to 350°C maximum. The F30J2K5E specifies a minimum operating temperature of –55°C, providing extended low-temperature capability.

4. Inventory and Packaging: The F40J2K5 is supplied in box packaging with 1,026 units in stock. The F30J2K5E is supplied in bulk packaging with 749 units in stock.

Frequently Asked Questions (FAQ)

Q: Can the F30J2K5E replace the F40J2K5 in all applications?

A: No. The F30J2K5E is rated for 30 watts maximum, while the F40J2K5 is rated for 40 watts. Substitution is valid only when the actual power dissipation in the circuit does not exceed 30 watts. Exceeding this limit will cause the F30J2K5E to overheat and fail prematurely.

Q: What are the physical differences between these parts?

A: The F30J2K5E is physically smaller than the F40J2K5. The F30J2K5E measures 1.250" L × 1.000" W (31.75 mm × 25.40 mm), while the F40J2K5 measures 2.000" L × 1.000" W (50.80 mm × 25.40 mm). Both have identical height when seated at 0.563" (14.29 mm). Verify that the smaller footprint of the F30J2K5E fits within your circuit board layout.

Q: Are these parts mechanically compatible?

A: Yes. Both parts feature identical mounting features (Flange Braces, Right Angle), lead style (Solder Lugs), and package type (Radial, Flat Oval). The mounting interface is identical; however, the smaller physical dimensions of the F30J2K5E must be accommodated in the PCB layout.

Q: What is the difference in RoHS compliance?

A: The F40J2K5 is RoHS non-compliant. The F30J2K5E is RoHS3 compliant. If your application or end market requires RoHS compliance, the F30J2K5E is the appropriate choice, provided power requirements do not exceed 30 watts.

Q: Do these parts have the same electrical characteristics?

A: Yes. Both parts have identical resistance (2.5 kOhms), tolerance (±5%), temperature coefficient (±260 ppm/°C), and composition (Wirewound). Electrical performance is equivalent within the power rating limits of each part.

Q: What happens if I use the F30J2K5E in a 40-watt application?

A: The F30J2K5E will exceed its thermal design limit and experience accelerated degradation. Resistance value may drift, coating integrity may be compromised, and the part may fail catastrophically. Use only within the 30-watt power rating.