BK/MDL-1/8 Equivalent & Substitute Parts

Part Overview

The BK/MDL-1/8 is a 125 mA, 250 V AC/DC slow-blow glass fuse cartridge manufactured by Eaton - Electronics Division. This component is classified as obsolete and requires a compatible fuse holder for installation. The 3AB/3AG package format with 1/4" x 1-1/4" dimensions is a standard industrial fuse specification. Due to its obsolete status, equivalent and substitute parts from active product lines are available to maintain circuit protection functionality in existing and new designs.

Substiute Parts

BK/MDL-1/8

Eaton - Electronics DivisionIn Stock: 788BK/MDL-1/8 Datasheet

Current PartRFQ

BK/MDL-1/8-R

Eaton - Electronics DivisionIn Stock: 5146BK/MDL-1/8-R Datasheet

DirectRFQ

MDL-1/8-R

Eaton - Electronics DivisionIn Stock: 809MDL-1/8-R Datasheet

DirectRFQ

BK/MDQ-1/8

Eaton - Electronics DivisionIn Stock: 831BK/MDQ-1/8 Datasheet

Parametric EquivalentRFQ

MDQ-1/8

Eaton - Electronics DivisionIn Stock: 700MDQ-1/8 Datasheet

Parametric EquivalentRFQ

0034.5208

SCHURTER Inc.In Stock: 12940034.5208 Datasheet

DirectRFQ

0313.125HXP

Littelfuse Inc.In Stock: 11080313.125HXP Datasheet

SimilarRFQ

0313.125MXP

Littelfuse Inc.In Stock: 18240313.125MXP Datasheet

Parametric EquivalentRFQ

0313.125VXP

Littelfuse Inc.In Stock: 7920313.125VXP Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BK/MDL-1/8 is determined by strict equivalence across the following critical parameters:

Mandatory Matching Parameters:

• Current Rating: 125 mA
• Voltage Rating (AC): 250 V
• Response Time: Slow Blow
• Fuse Type: Cartridge, Glass
• Package / Case: 3AB, 3AG, 1/4" x 1-1/4"
• Size / Dimension: 0.250" Dia x 1.250" L (6.35mm x 31.75mm)
• Breaking Capacity @ Rated Voltage: 35A
• Mounting Type: Requires Holder

All substitute parts listed below meet these mandatory parameters and are therefore electrically and mechanically compatible with the original BK/MDL-1/8 specification. Variations in secondary parameters such as DC cold resistance, melting I²t, and RoHS compliance do not affect functional substitution but may influence selection based on regulatory or environmental requirements.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation for New Designs:

For applications requiring RoHS3 compliance and extended product lifecycle support, select from the active Littelfuse 313 series parts: 0313.125MXP, 0313.125HXP, or 0313.125VXP. These components carry CE, CSA, and UL certifications and are manufactured to current environmental standards.

Recommendation for Eaton-Specific Designs:

If design specifications require Eaton components, the BK/MDL-1/8-R or MDL-1/8-R are active production parts with RoHS compliance and CE certification in addition to CSA and UL approvals. These represent the direct evolution of the obsolete BK/MDL-1/8.

Alternative Eaton Options:

The BK/MDQ-1/8 and MDQ-1/8 are active Eaton alternatives with identical electrical and mechanical specifications. These parts maintain CSA and UL certifications but do not carry RoHS compliance status.

Compatibility Assurance:

All listed substitute parts are mechanically and electrically interchangeable with the BK/MDL-1/8 within the same 3AB/3AG fuse holder. No circuit modifications or holder changes are required for substitution.

Frequently Asked Questions (FAQ)

Q: Can I directly replace BK/MDL-1/8 with any of the listed substitute parts?

A: Yes. All substitute parts listed meet the mandatory electrical and mechanical parameters: 125 mA current rating, 250 V AC voltage rating, slow-blow response, 35A breaking capacity, and 3AB/3AG package format. Direct substitution is possible without circuit or holder modifications.

Q: What is the difference between BK/MDL-1/8-R and MDL-1/8-R?

A: Both are active Eaton MDL series fuses with identical electrical specifications. The primary difference is RoHS compliance status: BK/MDL-1/8-R is ROHS3 Compliant, while MDL-1/8-R is RoHS Compliant. Both carry CE, CSA, and UL certifications.

Q: Why should I choose Littelfuse 313 series over Eaton alternatives?

A: The Littelfuse 313 series (0313.125MXP, 0313.125HXP, 0313.125VXP) offers ROHS3 compliance, CE certification, and active production status with established long-term availability. Selection depends on design requirements and supplier relationships.

Q: Are there differences in DC cold resistance between substitute parts?

A: Yes. DC cold resistance varies across the substitute parts (ranging from 9.85 to 30 Ohms). However, this parameter does not affect functional substitution for standard circuit protection applications. Verify DC cold resistance specifications only if your application has specific impedance requirements.

Q: What is the significance of "Slow Blow" response time?

A: Slow-blow fuses tolerate temporary inrush currents without nuisance tripping, making them suitable for circuits with startup transients. All substitute parts maintain this slow-blow characteristic, ensuring protection behavior identical to the original BK/MDL-1/8.

Q: Can I use parts marked as "Obsolete" as substitutes?

A: The SCHURTER 0034.5208 is marked obsolete but remains electrically and mechanically equivalent. However, for new designs or long-term applications, active production parts (Littelfuse 313 series or Eaton MDL-1/8-R) are preferred to ensure future availability and support.

Q: Do all substitute parts fit in the same fuse holder?

A: Yes. All substitute parts share the identical 3AB/3AG package format and 0.250" Dia x 1.250" L (6.35mm x 31.75mm) dimensions. No holder replacement or modification is required.

Q: Which substitute part has the best regulatory compliance?

A: The Littelfuse 313 series parts (0313.125MXP, 0313.125HXP, 0313.125VXP) carry the broadest certification set: CE, CSA, and UL. These are recommended for applications requiring international regulatory compliance.