5MF 125-R Equivalent & Substitute Parts

Part Overview

The 5MF 125-R is a 125 mA, 250 V AC/DC fast-blow glass cartridge fuse manufactured by Bel Fuse Inc. in a 5mm x 20mm package format. This component is classified as obsolete, necessitating identification of active equivalent alternatives that maintain identical electrical and mechanical specifications for direct replacement in existing applications.

Key Parameters

Parameter	Value
Current Rating	125 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Fast Blow
Package / Case	5mm x 20mm
Mounting Type	Requires Holder
Operating Temperature Range	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following parameters: current rating (125 mA), voltage rating (250 V AC), fuse type (cartridge glass), response time (fast blow), and physical package dimensions (5mm x 20mm). All identified substitutes maintain these core electrical and mechanical specifications. Secondary parameters including breaking capacity, melting I²t, DC cold resistance, and approval agencies vary among substitutes but do not preclude functional equivalence within the specified electrical envelope.

Parameter Comparison

Part Number	Manufacturer	Current Rating (mA)	Voltage Rating (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status
5MF 125-R	Bel Fuse Inc.	125	250	Fast Blow	5mm x 20mm	200	0.0017	6.92	Obsolete
0235.125MXP	Littelfuse Inc.	125	250	Fast Blow	5mm x 20mm	35	0.00273	5.75	Active
0034.1507	SCHURTER Inc.	125	250	Fast Blow	5mm x 20mm	35	0.00484	—	Active
0217.125HXP	Littelfuse Inc.	125	250	Fast Blow	5mm x 20mm	35	0.00478	3.82	Active
0217.125MXP	Littelfuse Inc.	125	250	Fast Blow	5mm x 20mm	35	0.00478	3.82	Active
0235.125HXP	Littelfuse Inc.	125	250	Fast Blow	5mm x 20mm	35	0.00273	5.75	Active
BK/GDB-125MA	Eaton - Electronics Division	125	250	Fast Blow	5mm x 20mm	35	0.005	2.8	Active
BK/GMA-125-R	Eaton - Electronics Division	125	250	Fast Blow	5mm x 20mm	35	0.0024	4.895	Active
BK/S500-125-R	Eaton - Electronics Division	125	250	Fast Blow	5mm x 20mm	35	0.005	2.8	Active
BK1/GMA-125-R	Eaton - Electronics Division	125	250	Fast Blow	5mm x 20mm	35	0.0024	4.895	Active
BK1/S500-125-R	Eaton - Electronics Division	125	250	Fast Blow	5mm x 20mm	35	0.005	2.8	Active

Engineering Selection Recommendations

All listed substitute parts are classified as active products and maintain full electrical and mechanical compatibility with the 5MF 125-R across the specified operating parameters. Selection among substitutes should prioritize parts with active product status and comprehensive approval certifications.

Littelfuse 0217.125HXP and 0217.125MXP offer the broadest certification coverage (CCC, CE, CSA, K-MARK, SEMKO, UL, VDE) and represent primary alternatives. Eaton BK/GMA-125-R and BK1/GMA-125-R provide CSA, PSE, and UL certifications with active status. SCHURTER 0034.1507 maintains CCC, cURus, and VDE approvals.

All substitutes comply with ROHS3 requirements and operate within the -55°C to 125°C temperature range specified for the original component.

Frequently Asked Questions (FAQ)

Q: Can any of these substitute parts be used as a direct replacement for the 5MF 125-R?

A: Yes. All listed parts maintain identical current rating (125 mA), voltage rating (250 V AC), fuse type (cartridge glass), response time (fast blow), and physical dimensions (5mm x 20mm). Direct mechanical and electrical substitution is supported.

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

A: The original 5MF 125-R specifies 200A breaking capacity, while most substitutes specify 35A. Both values exceed the rated current and remain within acceptable limits for this fuse category. The difference reflects manufacturing design variations but does not affect functional equivalence at the specified 125 mA operating point.

Q: How do DC cold resistance variations affect part selection?

A: DC cold resistance values range from 2.8 Ω to 6.92 Ω across the part family. These variations are inherent to different manufacturing processes and do not preclude substitution. Selection should be based on application-specific circuit requirements if resistance characteristics are critical.

Q: Are all substitute parts available in the same packaging format?

A: Yes. All substitute parts are supplied in 5mm x 20mm cartridge format and require the same holder type as the original 5MF 125-R. Physical installation compatibility is maintained across all alternatives.

Q: Which substitute offers the best certification coverage?

A: Littelfuse 0217.125HXP and 0217.125MXP provide the most comprehensive approval certifications: CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE. These parts are suitable for applications requiring multiple regional compliance standards.

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