5MF 125 Glass Cartridge Fuse - Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5MF 125 is a 125 mA, 250 V AC/DC fast-blow glass cartridge fuse in 5mm x 20mm form factor, designed for circuit protection applications requiring holder mounting. This part is classified as obsolete, making equivalent substitutes necessary for ongoing procurement and system maintenance. Substitute parts must maintain identical electrical ratings, mechanical dimensions, and functional characteristics to ensure direct compatibility without circuit redesign.

Substiute Parts

5MF 125

Bel Fuse Inc.In Stock: 9985MF 125 Datasheet

Current PartRFQ

0034.1507

SCHURTER Inc.In Stock: 10730034.1507 Datasheet

SimilarRFQ

0217.125HXP

Littelfuse Inc.In Stock: 11220217.125HXP Datasheet

SimilarRFQ

0235.125HXP

Littelfuse Inc.In Stock: 9740235.125HXP Datasheet

SimilarRFQ

S500-125-R

Eaton - Electronics DivisionIn Stock: 799S500-125-R Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 5MF 125 is determined by strict equivalence across the following parameters:

• Current Rating: 125 mA (exact match required)
• Voltage Rating: 250 V AC (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Fast Blow (exact match required)
• Physical Dimensions: 5mm x 20mm (exact match required)
• Mounting Configuration: Requires Holder (exact match required)

All qualified substitute parts listed below meet these criteria. Variations in secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and approval certifications do not disqualify substitution but may influence selection based on application-specific requirements.

Parameter Comparison

Engineering Selection Recommendations

All four substitute parts (0034.1507, 0217.125HXP, 0235.125HXP, S500-125-R) are electrically and mechanically equivalent to the 5MF 125 and provide direct substitution capability.

For new designs and ongoing procurement, active-status parts are preferred over obsolete inventory. The Littelfuse 0217.125HXP and 0235.125HXP, SCHURTER 0034.1507, and Eaton S500-125-R all maintain active product status and ROHS3 compliance, supporting long-term supply chain continuity.

Selection among active substitutes may be influenced by approval certifications required for specific applications. The Littelfuse 0217.125HXP carries the broadest certification portfolio (CCC, CE, CSA, K-MARK, SEMKO, UL, VDE), while the Littelfuse 0235.125HXP supports CE, CSA, KC, and UL certifications. The SCHURTER 0034.1507 provides CCC, cURus, and VDE approvals. The Eaton S500-125-R does not specify approval certifications in available data.

Frequently Asked Questions (FAQ)

Q: Can the 5MF 125 be directly replaced with any of the listed substitutes?

A: Yes. All four substitute parts meet the mandatory equivalence criteria: 125 mA current rating, 250 V AC voltage rating, fast-blow response, glass cartridge type, 5mm x 20mm dimensions, and holder-mount configuration. Physical and electrical compatibility is confirmed.

Q: What is the significance of the different breaking capacity values?

A: The main part (5MF 125) specifies 200 A breaking capacity, while all substitutes specify 35 A. Breaking capacity defines the maximum fault current the fuse can safely interrupt. The lower breaking capacity of substitutes does not affect substitution validity for applications within the 35 A fault current envelope. Applications requiring 200 A breaking capacity must retain the original 5MF 125 or identify alternative parts with matching breaking capacity.

Q: Why do substitute parts have different melting I²t and DC cold resistance values?

A: These parameters reflect design differences between manufacturers but do not disqualify substitution. Melting I²t (thermal energy required to melt the fuse element) and DC cold resistance are secondary characteristics that may influence response behavior in specific circuit conditions. For standard circuit protection applications, these variations are within acceptable engineering tolerance. Applications with critical thermal or resistance requirements should verify compatibility with the specific substitute selected.

Q: Are all substitutes RoHS compliant?

A: The original 5MF 125 is RoHS non-compliant. All four substitutes are ROHS3 compliant, supporting modern procurement and environmental compliance requirements. This represents an improvement over the obsolete original part.

Q: Which substitute offers the best certification coverage?

A: The Littelfuse 0217.125HXP provides the most comprehensive approval certifications: CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE. This part is suitable for applications requiring multiple regional or industry-specific certifications.

Q: Can substitutes be mixed in the same circuit or system?

A: Yes, all substitutes are electrically and mechanically equivalent and can be used interchangeably. However, for consistency and supply chain management, using a single substitute part number across a system is recommended to simplify inventory control and maintenance procedures.