MQ 250 Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. MQ 250 is a 250 mA, 125 V AC/DC board mount axial fuse with fast blow response time, designed for through-hole PCB applications. This part is classified as obsolete, making equivalent substitutes necessary for ongoing production and maintenance requirements. The MQ 250 meets CE, CSA, and cURus approval standards with an operating temperature range of -55°C to 125°C.

Substiute Parts

MQ 250

Bel Fuse Inc.In Stock: 773MQ 250 Datasheet

Current PartRFQ

0251.250MXL

LittelfuseIn Stock: 10320251.250MXL Datasheet

DirectRFQ

0251.250NRT1L

Littelfuse Inc.In Stock: 1123350251.250NRT1L Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the MQ 250 is determined by strict equivalence across electrical and mechanical parameters. All substitute parts must match the following criteria:

• Current rating: 250 mA
• Voltage rating: 125 V AC and 125 V DC
• Response time: Fast Blow
• Mounting type: Through Hole
• Fuse type: Board Mount (Cartridge Style Excluded)
• Package: Axial
• Breaking capacity: 50A AC, 300A DC
• Operating temperature range: -55°C to 125°C

The two qualified substitutes are both from Littelfuse Inc., PICO® II 251 series. These parts maintain electrical equivalence while offering active product status and improved availability compared to the obsolete MQ 250.

Parameter Comparison

Engineering Selection Recommendations

Both Littelfuse PICO® II 251 series parts (0251.250MXL and 0251.250NRT1L) are direct electrical equivalents to the obsolete MQ 250. Selection between these substitutes should be based on the following factors:

0251.250NRT1L (Cut Tape Packaging): This part offers the highest inventory availability (112,295 pcs) and is supplied in Cut Tape format suitable for automated assembly processes. It carries CSA and cURus certifications and is ROHS3 compliant. The REACH Affected status indicates compliance with REACH regulations.

0251.250MXL (Bulk Packaging): This part is supplied in bulk packaging and is suitable for manual assembly or reel-based processes. It maintains CSA and cURus certifications and ROHS3 compliance with REACH Unaffected status.

Both parts maintain the required electrical specifications and breaking capacity. The dimensional difference (0.110" vs 0.125" diameter) and resistance variance (0.665 vs 0.52 Ohms) are within acceptable tolerances for board mount axial fuse applications. The melting I²t difference reflects the updated design characteristics of the active PICO® II 251 series.

Frequently Asked Questions (FAQ)

Q: Can the 0251.250MXL and 0251.250NRT1L be used interchangeably with the MQ 250?

A: Yes. Both parts meet all electrical and mechanical equivalence criteria: 250 mA current rating, 125 V AC/DC voltage rating, fast blow response, 50A AC / 300A DC breaking capacity, and -55°C to 125°C operating temperature range. The primary difference is packaging format (bulk vs. cut tape).

Q: What is the impact of the dimensional difference between the MQ 250 and substitute parts?

A: The MQ 250 has a 0.125" diameter, while both Littelfuse substitutes have a 0.110" diameter. Both maintain the same 0.280" length. This dimensional change is within standard board mount axial fuse tolerances and does not affect electrical performance or PCB compatibility for standard through-hole applications.

Q: Does the DC cold resistance difference affect circuit performance?

A: The MQ 250 has 0.52 Ohms DC cold resistance, while the Littelfuse substitutes have 0.665 Ohms. This variance reflects design improvements in the PICO® II 251 series and remains within acceptable limits for fuse applications. Verify circuit design margins if resistance-sensitive applications are involved.

Q: Which substitute should be selected for new production designs?

A: For automated assembly processes, 0251.250NRT1L (cut tape) is recommended due to superior availability and standard reel packaging. For manual assembly or lower-volume applications, 0251.250MXL (bulk) provides equivalent electrical performance with flexible packaging options.

Q: Are there compliance differences between the substitutes?

A: Both parts carry CSA and cURus certifications. The 0251.250NRT1L is REACH Affected, while 0251.250MXL is REACH Unaffected. Both are ROHS3 compliant. Verify REACH compliance requirements for your specific application and end market.