Equivalent & Substitute Parts for 3SB 1.25

Part Overview

The Bel Fuse Inc. 3SB 1.25 is a 1.25 A, 250 V AC/DC slow-blow glass cartridge fuse designed for 3AB and 3AG holder applications. This part is classified as obsolete, making identification of equivalent and substitute components essential for ongoing system maintenance and new design implementations. Substitute parts must maintain identical electrical ratings, mechanical dimensions, and holder compatibility to ensure direct interchangeability without circuit modification.

Substiute Parts

3SB 1.25

Bel Fuse Inc.In Stock: 10953SB 1.25 Datasheet

Current PartRFQ

3SB 1.25-R

Bel Fuse Inc.In Stock: 45133SB 1.25-R Datasheet

DirectRFQ

0034.5227

SCHURTER Inc.In Stock: 8860034.5227 Datasheet

DirectRFQ

03131.25HXP

Littelfuse Inc.In Stock: 110603131.25HXP Datasheet

DirectRFQ

03131.25MXP

Littelfuse Inc.In Stock: 223103131.25MXP Datasheet

DirectRFQ

03131.25VXP

Littelfuse Inc.In Stock: 73403131.25VXP Datasheet

DirectRFQ

TSA-1.25A

OptiFuseIn Stock: 6519TSA-1.25A Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict compliance with the following parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating: 250 V AC (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Slow Blow (exact match required)
• Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
• Mounting Type: Requires Holder (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (minimum requirement)

All substitute parts listed below meet these mandatory criteria. Variations in secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and RoHS compliance status do not affect functional interchangeability within the specified electrical and mechanical constraints.

Parameter Comparison

Engineering Selection Recommendations

All listed substitute parts satisfy the mandatory electrical and mechanical compatibility requirements for direct replacement of the 3SB 1.25 fuse.

For new designs and ongoing production applications, the 3SB 1.25-R (Bel Fuse Inc.) is the primary recommended substitute. This part maintains manufacturer continuity, carries active product status, and provides enhanced breaking capacity (200A versus 100A). It includes expanded regulatory approvals (cULus certification) and meets ROHS3 compliance requirements.

For applications requiring alternative manufacturer sourcing, the Littelfuse 313 series (03131.25HXP, 03131.25MXP, 03131.25VXP) provides active product status with full regulatory compliance (CE, CSA, PSE, UL) and ROHS3 certification. These three part numbers are functionally equivalent; selection among them may be based on packaging availability and inventory considerations.

The SCHURTER 0034.5227 and OptiFuse TSA-1.25A are functionally compatible substitutes with active product status. The SCHURTER part carries obsolete designation despite current availability. The OptiFuse TSA-1.25A provides the lowest melting I²t value (5.789) among all listed substitutes, which may influence thermal response characteristics in specific circuit applications.

Frequently Asked Questions (FAQ)

Q: Can the 3SB 1.25 be replaced with any of the listed substitute parts without circuit modification?

A: Yes. All listed substitute parts maintain identical current rating (1.25 A), voltage rating (250 V AC), fuse type (cartridge, glass), response time (slow blow), and holder compatibility (3AB, 3AG). Direct mechanical and electrical interchangeability is assured.

Q: What is the significance of the different melting I²t values among substitute parts?

A: Melting I²t is a thermal characteristic that influences the fuse's response to overcurrent conditions. While all parts are classified as slow-blow fuses, variations in melting I²t (ranging from 5.789 to 25.4 across the listed substitutes) may result in slightly different thermal response profiles. For applications with specific thermal requirements, this parameter should be cross-referenced with circuit design specifications.

Q: Are there dimensional differences between substitute parts?

A: Minor dimensional variations exist. The 3SB 1.25 and 3SB 1.25-R measure 0.250" Dia x 1.252" L (6.35mm x 31.80mm), while Littelfuse and SCHURTER parts measure 0.250" Dia x 1.250" L (6.35mm x 31.75mm). These differences (0.002" or 0.05mm in length) are within standard mechanical tolerances for 3AB and 3AG holder applications and do not affect functional compatibility.

Q: Which substitute part offers the best long-term availability?

A: The 3SB 1.25-R (Bel Fuse Inc.) and the Littelfuse 313 series (03131.25HXP, 03131.25MXP, 03131.25VXP) carry active product status, indicating ongoing manufacturer support and production. These parts are recommended for applications requiring extended supply chain stability.

Q: What regulatory certifications should I verify for my specific application?

A: All substitute parts carry UL and CSA certifications. The 3SB 1.25-R includes cULus certification. Littelfuse parts include CE and PSE certifications in addition to UL and CSA. Verify that the selected substitute meets all regulatory requirements mandated by your application's end-use jurisdiction and industry standards.