Equivalent & Substitute Parts for BK/EFF-4 Board Mount Fuse

Part Overview

The BK/EFF-4 is a 4 A 250 V AC/DC board mount fuse manufactured by Eaton - Electronics Division, designed for through-hole radial mounting in vertical orientation. This component is classified as obsolete product status. Due to its obsolete classification, equivalent substitute parts with active product status are available to maintain design continuity and ensure ongoing component availability for production and maintenance applications.

Substiute Parts

BK/EFF-4

Eaton - Electronics DivisionIn Stock: 712BK/EFF-4 Datasheet

Current PartRFQ

SR-5F-4A-BK

Eaton - Electronics DivisionIn Stock: 895SR-5F-4A-BK Datasheet

SimilarRFQ

MRF 4-AMMO

Bel Fuse Inc.In Stock: 1205MRF 4-AMMO Datasheet

DirectRFQ

MRF 4-BULK

Bel Fuse Inc.In Stock: 1104MRF 4-BULK Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BK/EFF-4 is determined by strict equivalence across the following critical parameters:

Mandatory Matching Parameters:

• Current Rating: 4 A
• Voltage Rating (AC): 250 V
• Mounting Type: Through Hole
• Fuse Type: Board Mount (Cartridge Style Excluded)
• Package / Case: Radial, Can, Vertical
• Response Time: Fast Blow

Acceptable Variation Parameters:

• Physical dimensions within manufacturing tolerance (0.329" ± tolerance and 0.303" ± tolerance)
• DC Cold Resistance within operational limits
• Melting I²t values within fast-blow characteristic range
• Operating temperature range (minimum -40°C acceptable; maximum 125°C required)
• Breaking Capacity at rated voltage (40 A or higher acceptable)

The substitute parts SR-5F-4A-BK, MRF 4-AMMO, and MRF 4-BULK meet all mandatory matching parameters and are therefore direct functional equivalents for the BK/EFF-4.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Identical Footprint and Performance):

MRF 4-AMMO and MRF 4-BULK are preferred substitutes. Both parts maintain identical physical dimensions (0.329" Dia x 0.303" H), matching the original BK/EFF-4 footprint precisely. Both are manufactured by Bel Fuse Inc. with active product status and carry comprehensive international certifications including AEC-Q200, CE, CSA, cULus, PSE, SEMKO, and VDE. Operating temperature range (-55°C ~ 125°C) matches the original specification. DC Cold Resistance (0.011 Ohms) is lower than the original (0.012 Ohms), indicating superior electrical performance. Breaking Capacity (40 A) exceeds minimum requirements.

For Applications with Dimensional Tolerance:

SR-5F-4A-BK (Eaton - Electronics Division) is an alternative from the original manufacturer. This part has active product status and carries cULus and PSE certifications. Physical dimensions differ slightly (0.335" Dia x 0.319" H), requiring PCB layout verification. Operating temperature minimum is -40°C (versus -55°C for original), which may be limiting in extreme cold environments. DC Cold Resistance (0.026 Ohms) is elevated compared to the original specification.

Packaging Considerations:

MRF 4-AMMO is supplied in Tape & Box (TB) packaging, suitable for automated assembly processes. MRF 4-BULK and SR-5F-4A-BK are supplied in Bulk packaging, suitable for manual assembly or reel-fed operations.

Frequently Asked Questions (FAQ)

Q: Can SR-5F-4A-BK be used as a direct replacement for BK/EFF-4 on existing PCBs?

A: SR-5F-4A-BK has different physical dimensions (0.335" Dia x 0.319" H versus 0.329" Dia x 0.303" H). PCB hole spacing and component clearance must be verified before substitution. If the original PCB was designed with tight tolerances, dimensional differences may cause fit issues.

Q: What is the difference between MRF 4-AMMO and MRF 4-BULK?

A: Both parts are electrically and mechanically identical. The difference is packaging: MRF 4-AMMO is supplied in Tape & Box (TB) format for automated pick-and-place assembly, while MRF 4-BULK is supplied in bulk form for manual assembly or alternative handling methods.

Q: Are all substitute parts RoHS compliant?

A: MRF 4-AMMO and MRF 4-BULK are ROHS3 Compliant. SR-5F-4A-BK does not specify RoHS status in the provided data. The original BK/EFF-4 does not specify RoHS status.

Q: Which substitute has the lowest DC Cold Resistance?

A: MRF 4-AMMO and MRF 4-BULK both have DC Cold Resistance of 0.011 Ohms, which is lower than the original BK/EFF-4 (0.012 Ohms) and significantly lower than SR-5F-4A-BK (0.026 Ohms).

Q: Can these parts be used in applications requiring -55°C operation?

A: MRF 4-AMMO, MRF 4-BULK, and BK/EFF-4 all support -55°C minimum operating temperature. SR-5F-4A-BK supports only -40°C minimum, making it unsuitable for applications requiring -55°C operation.

Q: What certifications are most comprehensive among the substitutes?

A: MRF 4-AMMO and MRF 4-BULK carry the most comprehensive certification portfolio: AEC-Q200, CE, CSA, cULus, PSE, SEMKO, and VDE. The original BK/EFF-4 carries SEMKO and UL certifications. SR-5F-4A-BK carries cULus and PSE certifications.