MJS 4 Equivalent & Substitute Parts

Part Overview

The MJS 4 is a 4A 250VAC slow-blow glass cartridge fuse in 2AG package format (5mm x 15mm axial). Manufactured by Bel Fuse Inc., this through-hole component is designed for circuit protection applications requiring moderate current ratings and slow-blow response characteristics. The main part (MJS 4) carries an obsolete product status, making identification of active equivalent alternatives essential for ongoing procurement and system maintenance. The MJS 4-R variant provides a direct functional equivalent with active product status and improved compliance characteristics.

Substiute Parts

MJS 4

Bel Fuse Inc.In Stock: 968MJS 4 Datasheet

Current PartRFQ

MJS 4-R

Bel Fuse Inc.In Stock: 930MJS 4-R Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

The MJS 4-R qualifies as a direct substitute for the MJS 4 based on identical electrical and mechanical parameters:

Critical Matching Parameters:

• Current Rating: 4 A (identical)
• Voltage Rating (AC): 250 V (identical)
• Fuse Type: Cartridge, Glass (identical)
• Package / Case: 2AG, 5mm x 15mm (Axial) (identical)
• Response Time: Slow Blow (identical)
• Breaking Capacity @ Rated Voltage: 200A (identical)
• Melting I²t: 86 (identical)
• Operating Temperature Range: -55°C ~ 125°C (identical)
• Physical Dimensions: 0.217" Dia x 0.591" L (5.50mm x 15.00mm) (identical)

The MJS 4-R maintains full electrical and mechanical compatibility with the original MJS 4 specification. Both components are manufactured by Bel Fuse Inc. within the same MJS series and share identical performance characteristics for circuit protection applications.

Parameter Comparison

Engineering Selection Recommendations

The MJS 4-R is the appropriate selection for new designs and ongoing procurement applications. While the original MJS 4 carries obsolete product status, the MJS 4-R maintains identical electrical and mechanical specifications, ensuring direct functional compatibility in existing circuit protection applications.

The MJS 4-R offers improved compliance posture through ROHS3 certification, whereas the MJS 4 is RoHS non-compliant. Both components carry equivalent international approvals (CE, CSA, PSE) with the MJS 4-R additionally certified to cULus standards. The DC cold resistance differential (0.023 Ohms vs. 0.031 Ohms) represents a minor improvement in the substitute part and does not affect circuit protection performance at the specified 4A rating.

For applications requiring the MJS 4 specification, the MJS 4-R provides a direct replacement with active product status and enhanced regulatory compliance.

Frequently Asked Questions (FAQ)

Q: Can the MJS 4-R directly replace the MJS 4 in existing applications?

A: Yes. The MJS 4-R maintains identical electrical ratings (4A, 250VAC), fuse type (cartridge, glass), package format (2AG, 5mm x 15mm), response time (slow blow), and breaking capacity (200A). Physical dimensions and mounting type are identical, enabling direct board-level substitution.

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

A: The MJS 4 carries obsolete status, indicating discontinued manufacturing and limited availability. The MJS 4-R is active, ensuring reliable procurement for current and future applications. For new designs or system refreshes, the MJS 4-R is the appropriate selection.

Q: How do the DC cold resistance values affect substitution?

A: The MJS 4-R exhibits lower DC cold resistance (0.023 Ohms vs. 0.031 Ohms). This minor difference does not impact circuit protection performance at the 4A rating and represents an improvement in the substitute part. Both values fall within acceptable ranges for slow-blow cartridge fuses in this current class.

Q: Are there compliance differences between the two parts?

A: The MJS 4-R is ROHS3 compliant, while the MJS 4 is RoHS non-compliant. Both carry CE, CSA, and PSE certifications. The MJS 4-R additionally holds cULus certification. For applications subject to RoHS requirements, the MJS 4-R is the required selection.

Q: Is the 2AG package format standard for both parts?

A: Yes. Both the MJS 4 and MJS 4-R use the 2AG cartridge format (5mm diameter x 15mm length, axial orientation). This standardized package ensures mechanical compatibility with existing fuse holders and PCB layouts.