3JS 1.25 Equivalent & Substitute Parts

Part Overview

The 3JS 1.25 is a 1.25 A slow-blow glass cartridge fuse rated for 350 V AC and 140 V DC operation. Manufactured by Bel Fuse Inc., this through-hole component features a 2AG form factor with 5mm x 15mm dimensions. The main part (3JS 1.25) carries an obsolete product status, making identification of active equivalent parts essential for ongoing system support and procurement planning.

Substiute Parts

3JS 1.25

Bel Fuse Inc.In Stock: 8853JS 1.25 Datasheet

Current PartRFQ

3JS 1.25-R

Bel Fuse Inc.In Stock: 20263JS 1.25-R Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 3JS 1.25 is determined by strict equivalence across the following critical parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating - AC: 350 V (exact match required)
• Voltage Rating - DC: 140 V (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Slow Blow (exact match required)
• Package / Case: 2AG, 5mm x 15mm (Axial) (exact match required)
• Mounting Type: Through Hole (exact match required)
• Breaking Capacity @ Rated Voltage: 100A AC, 150A DC (exact match required)
• Melting I²t: 9.3 (exact match required)
• Approval Agency: CE, CSA, cURus, PSE (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (exact match required)

The 3JS 1.25-R meets all substitution criteria and is classified as a direct equivalent.

Parameter Comparison

Engineering Selection Recommendations

The 3JS 1.25-R is the direct active equivalent for the obsolete 3JS 1.25. Both parts maintain identical electrical and mechanical specifications across all critical parameters: current rating, voltage ratings, fuse type, response time, package form factor, breaking capacity, and thermal characteristics.

The 3JS 1.25-R offers improved compliance status. It carries ROHS3 compliance, whereas the main part is RoHS non-compliant. Both parts maintain equivalent regulatory approvals (CE, CSA, cURus, PSE) and REACH unaffected status.

The DC cold resistance differs between the two parts (0.195 Ohms versus 0.13 Ohms), reflecting manufacturing process improvements in the active variant. This parameter does not affect functional substitution for circuit protection applications.

For new designs and ongoing procurement, the 3JS 1.25-R is the appropriate selection due to its active product status and improved compliance profile.

Frequently Asked Questions (FAQ)

Q: Can the 3JS 1.25-R be used as a direct replacement for the 3JS 1.25?

A: Yes. The 3JS 1.25-R is a direct equivalent. All critical electrical parameters (current rating, voltage ratings, breaking capacity, melting I²t) and mechanical specifications (package form factor, dimensions, mounting type) are identical. The parts are functionally interchangeable in circuit protection applications.

Q: Why does the DC cold resistance differ between the two parts?

A: The DC cold resistance values (0.195 Ohms for 3JS 1.25 and 0.13 Ohms for 3JS 1.25-R) reflect manufacturing process refinements. This parameter does not affect the fuse's primary function as a circuit protection device and does not impact substitution compatibility.

Q: What is the significance of the product status difference?

A: The 3JS 1.25 is classified as obsolete, indicating it is no longer in active production. The 3JS 1.25-R maintains active product status, ensuring ongoing availability and support. For new procurement and system maintenance, the active part is the appropriate choice.

Q: Are there compliance differences between the two parts?

A: Both parts carry identical regulatory approvals (CE, CSA, cURus, PSE) and REACH unaffected status. The 3JS 1.25-R is ROHS3 compliant, while the main part is RoHS non-compliant. For applications requiring RoHS compliance, the 3JS 1.25-R is the required selection.

Q: What packaging options are available?

A: The 3JS 1.25 is available in standard packaging. The 3JS 1.25-R is supplied in bulk packaging, which may affect procurement quantities and logistics planning.