Equivalent & Substitute Parts for 5VT 1.25

Part Overview

The Bel Fuse Inc. 5VT 1.25 is a 1.25 A, 250 V AC/DC glass cartridge fuse with 5mm x 20mm dimensions and slow-blow response characteristics. This part is classified as obsolete. Equivalent and substitute parts are necessary to maintain circuit protection functionality in applications where the original component is no longer available or where design requirements necessitate alternative specifications such as improved breaking capacity, enhanced RoHS compliance, or broader regulatory certifications.

Key Parameters

Parameter	5VT 1.25
Current Rating	1.25 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35 A
Melting I²t	42
DC Cold Resistance	0.08 Ohms
Operating Temperature	-55°C ~ 125°C
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following parameters:

Current Rating: 1.25 A (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Requires Holder (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

All substitute parts listed meet these core electrical and mechanical parameters. Variations in breaking capacity, melting I²t, DC cold resistance, and regulatory certifications are noted but do not disqualify substitution when the above parameters align.

Parameter Comparison

Part Number	Manufacturer	Current Rating	Voltage (AC)	Package	Response Time	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance	Product Status	RoHS Status
5VT 1.25	Bel Fuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	35 A	42	0.08 Ohms	Obsolete	RoHS non-compliant
5ET 1.25-R	Bel Fuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	150 A	42	0.08 Ohms	Active	ROHS3 Compliant
5ST 1.25-R	Bel Fuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	35 A	4.1	0.06 Ohms	Active	ROHS3 Compliant
5TT 1.25-R	Bel Fuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	100 A	13.1	0.206 Ohms	Active	ROHS3 Compliant
02131.25MXP	Littelfuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	35 A	27.15	0.0817 Ohms	Active	ROHS3 Compliant
02181.25TXP	Littelfuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	35 A	12.65	0.0446 Ohms	Active	ROHS3 Compliant
02191.25MXAP	Littelfuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	150 A	27.15	0.0817 Ohms	Active	ROHS3 Compliant
02391.25HXP	Littelfuse Inc.	1.25 A	250 V	5mm x 20mm	Slow Blow	100 A	19.525	0.198 Ohms	Active	ROHS3 Compliant
BK1/GMD-1.25-R	Eaton - Electronics Division	1.25 A	250 V	5mm x 20mm	Slow Blow	100 A	16	0.1995 Ohms	Active	ROHS3 Compliant
GDC-1.25A	Eaton - Electronics Division	1.25 A	250 V	5mm x 20mm	Slow Blow	35 A	10.05	0.06 Ohms	Active	ROHS3 Compliant

Engineering Selection Recommendations

All listed substitute parts maintain electrical and mechanical equivalence to the 5VT 1.25 across current rating, voltage, package dimensions, response time, and operating temperature range. Selection among substitutes should be based on the following criteria:

Product Status: The 5VT 1.25 is obsolete. All substitute parts listed are active and available. Selection of an active part ensures continued supply chain access and manufacturing support.

RoHS Compliance: The 5VT 1.25 is RoHS non-compliant. All substitute parts are ROHS3 compliant, meeting current environmental and regulatory requirements for new designs and applications subject to RoHS directives.

Regulatory Certifications: The 5VT 1.25 carries CE, CSA, SEMKO, UL, and VDE approvals. Substitute parts from Bel Fuse Inc. (5ET 1.25-R, 5ST 1.25-R, 5TT 1.25-R) maintain broad certification coverage including CCC, CE, CSA, cURus, SEMKO, and VDE. Littelfuse and Eaton alternatives provide certifications aligned with specific regional and application requirements. Selection should match the regulatory environment of the target application.

Breaking Capacity Considerations: The 5VT 1.25 has a breaking capacity of 35 A. Substitute parts with higher breaking capacity (5ET 1.25-R at 150 A, 5TT 1.25-R at 100 A, 02191.25MXAP at 150 A, 02391.25HXP at 100 A, BK1/GMD-1.25-R at 100 A) provide enhanced fault protection margins. Parts with matching 35 A breaking capacity (5ST 1.25-R, 02131.25MXP, 02181.25TXP, GDC-1.25A) maintain direct electrical equivalence.

Frequently Asked Questions (FAQ)

Q: Can I substitute the 5VT 1.25 with any of the listed parts?

A: Yes. All listed parts meet the core substitution criteria: 1.25 A current rating, 250 V AC voltage rating, 5mm x 20mm package, slow-blow response, and -55°C to 125°C operating temperature range. Physical fit in existing fuse holders and electrical performance in the circuit are maintained.

Q: What is the difference between parts with 35 A breaking capacity and those with 100 A or 150 A?

A: Breaking capacity defines the maximum fault current the fuse can safely interrupt without rupturing or creating a hazard. Higher breaking capacity provides greater protection margin in circuits with higher available fault currents. Selection depends on the actual fault current available in your circuit. If the circuit's available fault current exceeds 35 A, a substitute with higher breaking capacity is required.

Q: Why is the 5VT 1.25 obsolete?

A: The 5VT 1.25 is classified as obsolete by the manufacturer. Active alternatives from Bel Fuse Inc., Littelfuse Inc., and Eaton provide equivalent functionality with current production status, improved RoHS compliance, and broader regulatory certifications.

Q: Does RoHS compliance affect electrical performance?

A: No. RoHS compliance relates to material composition and environmental safety, not electrical characteristics. All ROHS3 compliant substitutes maintain the same electrical performance as the original 5VT 1.25.

Q: Are there differences in melting I²t values among substitutes?

A: Yes. Melting I²t values vary among substitutes, ranging from 4.1 to 42. This parameter affects the thermal response of the fuse element. For direct electrical equivalence to the 5VT 1.25 (melting I²t of 42), the 5ET 1.25-R is the closest match. Other substitutes with different melting I²t values remain functionally equivalent for the specified current and voltage ratings but may exhibit different thermal response characteristics in transient conditions.

Q: Which substitute offers the best regulatory coverage?

A: The Littelfuse 02191.25MXAP provides the broadest regulatory certifications (CCC, CE, CSA, PSE, SEMKO, UL, VDE) and is suitable for global applications. Bel Fuse Inc. 5ET 1.25-R and 5TT 1.25-R also provide comprehensive certification coverage (CCC, CE, CSA, cURus, SEMKO, VDE and CE, CSA, cULus, PSE respectively).

Q: Can I use a substitute with higher breaking capacity in place of the original?

A: Yes. A substitute with higher breaking capacity is electrically and mechanically compatible and provides enhanced fault protection. No circuit modification is required. The fuse will still operate at 1.25 A and 250 V AC.

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