MDQ-1/8 Equivalent & Substitute Parts Reference

Part Overview

The MDQ-1/8 is a 125 mA, 250 V AC/DC slow-blow glass fuse cartridge manufactured by Eaton - Electronics Division. This component requires a 3AB or 3AG fuse holder and is housed in a 1/4" x 1-1/4" (6.35mm x 31.75mm) package. The part maintains active product status with 645 pieces currently in stock. Equivalent and substitute parts are identified based on matching electrical ratings, mechanical dimensions, fuse type, response characteristics, and approval certifications to ensure direct functional replacement in circuit protection applications.

Substiute Parts

MDQ-1/8

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

Current PartRFQ

BK/MDL-1/8-R

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

Parametric EquivalentRFQ

0034.5208

SCHURTER Inc.In Stock: 12940034.5208 Datasheet

Parametric EquivalentRFQ

0313.125HXP

Littelfuse Inc.In Stock: 11080313.125HXP Datasheet

Parametric EquivalentRFQ

0313.125MXP

Littelfuse Inc.In Stock: 18240313.125MXP Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the MDQ-1/8 are qualified based on the following critical parameters that must match or exceed the main part specifications:

Mandatory Matching Parameters:

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

All identified substitute parts meet these mandatory parameters. Variations in DC Cold Resistance, Melting I²t, and compliance certifications are documented but do not disqualify substitution eligibility when core electrical and mechanical specifications align.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute - BK/MDL-1/8-R (Eaton - Electronics Division): The BK/MDL-1/8-R is the preferred substitute for the MDQ-1/8. Both parts are manufactured by Eaton and share identical electrical and mechanical specifications. The BK/MDL-1/8-R carries CE, CSA, and UL approvals, providing broader international compliance coverage than the MDQ-1/8. This part maintains active product status with the highest inventory availability (5079 pieces), ensuring supply continuity.

Secondary Substitutes - 0313.125HXP and 0313.125MXP (Littelfuse Inc.): Both Littelfuse 313 series parts (0313.125HXP and 0313.125MXP) are functionally equivalent to the MDQ-1/8. These parts carry CE, CSA, and UL certifications and maintain active product status. Both are ROHS3 compliant with documented operating temperature ranges (-55°C ~ 125°C). The 0313.125MXP offers higher inventory availability (1781 pieces) compared to the 0313.125HXP (1030 pieces).

Tertiary Substitute - 0034.5208 (SCHURTER Inc.): The 0034.5208 meets all mandatory electrical and mechanical parameters and carries CSA and UL approvals. However, this part is classified as obsolete product status. Selection of this part should be limited to applications where existing inventory must be depleted or where legacy system compatibility is required.

Compliance Considerations: All substitute parts comply with ROHS3 and REACH requirements where specified. The Littelfuse and Eaton BK/MDL series parts provide the most comprehensive compliance documentation. Selection should prioritize parts with active product status to ensure long-term availability and support.

Frequently Asked Questions (FAQ)

Q: Can the BK/MDL-1/8-R directly replace the MDQ-1/8 without any circuit modifications?

A: Yes. The BK/MDL-1/8-R is a direct parametric equivalent with identical current rating (125 mA), voltage rating (250 V AC), response time (slow blow), and mechanical dimensions (0.250" Dia x 1.250" L). Both parts require the same 3AB or 3AG fuse holder. No circuit modifications are required.

Q: What is the difference between the Littelfuse 0313.125HXP and 0313.125MXP?

A: Both parts are functionally identical in terms of electrical ratings, mechanical dimensions, and approvals. The primary difference is inventory availability: the 0313.125MXP has 1781 pieces in stock compared to 1030 pieces for the 0313.125HXP. Both carry identical DC Cold Resistance (30 Ohms) and Melting I²t (0.152) specifications.

Q: Why is the 0034.5208 marked as obsolete?

A: The 0034.5208 is classified as obsolete product status by SCHURTER Inc. While it remains functionally equivalent to the MDQ-1/8 and maintains adequate inventory (1230 pieces), this designation indicates that the manufacturer is no longer actively producing or supporting this part. New designs should specify active-status alternatives.

Q: Are there any differences in DC Cold Resistance between the substitute parts?

A: Yes. The MDQ-1/8 has 21.5 Ohms, the BK/MDL-1/8-R has 12.238 Ohms, and both Littelfuse parts (0313.125HXP and 0313.125MXP) have 30 Ohms. These variations do not affect substitution eligibility, as all parts meet the 35A breaking capacity requirement at rated voltage. DC Cold Resistance differences are within acceptable tolerances for slow-blow fuse cartridges in this current class.

Q: Do all substitute parts fit the same 3AB and 3AG fuse holders?

A: Yes. All substitute parts share identical mechanical dimensions (0.250" Dia x 1.250" L / 6.35mm x 31.75mm) and are designed for 3AB and 3AG fuse holder compatibility. Physical installation is identical across all listed parts.

Q: Which substitute part offers the best compliance coverage?

A: The BK/MDL-1/8-R, 0313.125HXP, and 0313.125MXP all carry CE, CSA, and UL certifications. The MDQ-1/8 carries only CSA and UL approvals. For applications requiring CE compliance, any of these three substitutes provide broader regulatory coverage.

Q: What is the Melting I²t parameter, and why does it vary between parts?

A: Melting I²t is a thermal characteristic that describes the energy required to melt the fuse element. Variations in this parameter (ranging from 0.0422 to 0.288 across the listed parts) reflect differences in fuse element design and material composition. All parts maintain the same 125 mA current rating and slow-blow response time, ensuring consistent circuit protection behavior in standard applications.