3AG 125 mA 250V AC/DC Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 3AG 125 mA 250V AC/DC glass cartridge fuse (Bel Fuse Inc., part number 3AG 125) is a fast-blow fuse cartridge designed for circuit protection in applications requiring 125 mA current limiting at 250V AC/DC. This component requires a compatible holder (3AB or 3AG series) for installation. The main part is currently obsolete, making equivalent substitutes necessary for ongoing maintenance and new designs. Substitute parts must maintain identical electrical ratings, mechanical dimensions, and holder compatibility to ensure direct replacement capability.

Substiute Parts

3AG 125

Bel Fuse Inc.In Stock: 10323AG 125 Datasheet

Current PartRFQ

0312.125HXP

Littelfuse Inc.In Stock: 7310312.125HXP Datasheet

SimilarRFQ

BK/AGC-B-1/8

Eaton - Electronics DivisionIn Stock: 963BK/AGC-B-1/8 Datasheet

SimilarRFQ

FSA-125MA

OptiFuseIn Stock: 1603FSA-125MA Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 3AG 125 mA fuse is determined by strict equivalence across the following parameters:

• Current Rating: Must be exactly 125 mA
• Voltage Rating (AC): Must be 250 V minimum
• Fuse Type: Must be Cartridge, Glass
• Response Time: Must be Fast Blow
• Package / Case: Must be 3AB, 3AG compatible with 1/4" x 1-1/4" dimensions
• Operating Temperature Range: Must support -55°C ~ 125°C

All identified substitute parts meet these criteria and are mechanically and electrically interchangeable with the original 3AG 125 component. Substitutes are grouped by manufacturer and product status (active vs. obsolete).

Parameter Comparison

Engineering Selection Recommendations

For applications currently using the obsolete 3AG 125 component, the following active substitutes are available:

0312.125HXP (Littelfuse Inc.) and FSA-125MA (OptiFuse) are both ROHS3 compliant alternatives, meeting modern environmental and regulatory requirements. Both maintain full electrical and mechanical compatibility with the original 3AG 125 specification.

BK/AGC-B-1/8 (Eaton - Electronics Division) is an active product with CSA and UL certifications. While RoHS non-compliant, it provides a direct electrical and mechanical substitute for applications where RoHS compliance is not required.

All three substitutes are mechanically compatible with 3AB and 3AG holders and operate within the specified -55°C ~ 125°C temperature range. Selection should be based on regulatory compliance requirements (RoHS status), certification needs, and availability in your supply chain.

Frequently Asked Questions (FAQ)

Q: Can the 3AG 125 be directly replaced with any of these substitutes?

A: Yes. All listed substitutes (0312.125HXP, BK/AGC-B-1/8, and FSA-125MA) are mechanically and electrically interchangeable. They share identical current ratings (125 mA), voltage ratings (250V AC), fuse type (cartridge glass), response time (fast blow), and package dimensions (3AB/3AG, 1/4" x 1-1/4").

Q: What is the difference between these substitutes?

A: The primary differences are manufacturer, product status (all are active), RoHS compliance status, and regulatory certifications. 0312.125HXP and FSA-125MA are ROHS3 compliant; BK/AGC-B-1/8 is not. Breaking capacity and melting I²t values vary slightly but do not affect direct substitution capability.

Q: Do these substitutes require different holders?

A: No. All substitutes use the same 3AB and 3AG holder series as the original 3AG 125. No holder modifications or replacements are necessary.

Q: Which substitute should I choose for new designs?

A: For new designs, prioritize active products with ROHS3 compliance (0312.125HXP or FSA-125MA) to ensure long-term availability and regulatory alignment. Verify that the selected substitute's certifications (CE, CSA, UL) match your application requirements.

Q: Are there temperature or environmental limitations with these substitutes?

A: All substitutes operate within the same temperature range (-55°C ~ 125°C) as the original 3AG 125. No additional environmental restrictions apply beyond those of the original component.