MQ 7TR Equivalent & Substitute Parts

Part Overview

The MQ 7TR is a 7A 125VAC/VDC board mount axial fuse manufactured by Bel Fuse Inc. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing design support and procurement. The MQ 7TR serves as a fast-blow protection device in through-hole applications requiring 7 ampere current limiting at 125 volt AC and DC ratings.

Key Parameters

Parameter	Value
Current Rating	7 A
Voltage Rating - AC	125 V
Voltage Rating - DC	125 V
Response Time	Fast Blow
Mounting Type	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Breaking Capacity @ Rated Voltage	50A AC, 300A DC
Operating Temperature Range	-55°C ~ 125°C

Substitute Part Grouping Explanation

Substitute parts for the MQ 7TR are qualified based on electrical and mechanical parameter equivalence. The following criteria determine substitution validity:

Electrical Parameters (Must Match):

Current Rating: 7 A
Voltage Rating - AC: 125 V
Voltage Rating - DC: 125 V
Response Time: Fast Blow
Breaking Capacity @ Rated Voltage: 50A AC, 300A DC

Mechanical Parameters (Must Match):

Mounting Type: Through Hole
Fuse Type: Board Mount (Cartridge Style Excluded)
Package / Case: Axial
Operating Temperature Range: -55°C ~ 125°C

Acceptable Variations:

Physical dimensions may vary within functional tolerance (diameter and length)
DC Cold Resistance values within operational specification
Melting I²t values within acceptable thermal performance range
Packaging format (Cut Tape vs. other formats)
Approval agencies and compliance certifications

The following parts meet these substitution criteria:

0251007.NRT1L (Littelfuse Inc., PICO® II 251 Series)
0251007.MRT1L (Littelfuse Inc., PICO® II 251 Series)

Parameter Comparison

Parameter	MQ 7TR (Bel Fuse)	0251007.NRT1L (Littelfuse)	0251007.MRT1L (Littelfuse)
Current Rating (Amps)	7 A	7 A	7 A
Voltage Rating - AC	125 V	125 V	125 V
Voltage Rating - DC	125 V	125 V	125 V
Response Time	Fast Blow	Fast Blow	Fast Blow
Mounting Type	Through Hole	Through Hole	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)
Package / Case	Axial	Axial	Axial
Breaking Capacity @ Rated Voltage	50A AC, 300A DC	50A AC, 300A DC	50A AC, 300A DC
Melting I²t	8	10.4	10.4
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Size / Dimension	0.125" Dia x 0.280" L (3.18mm x 7.10mm)	0.110" Dia x 0.280" L (2.80mm x 7.11mm)	0.110" Dia x 0.280" L (2.80mm x 7.11mm)
DC Cold Resistance	0.012 Ohms	0.0107 Ohms	0.0107 Ohms
Product Status	Obsolete	Active	Active
Approval Agency	CE, CSA, cURus	CSA, cURus, TUV	CSA, cURus, TUV
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Both 0251007.NRT1L and 0251007.MRT1L are active production parts from Littelfuse Inc. and provide direct electrical equivalence to the obsolete MQ 7TR. Selection between these two substitute parts should be based on packaging availability and inventory requirements.

0251007.NRT1L is available in Cut Tape (CT) packaging with 175,060 pieces in stock, providing high availability for volume applications.

0251007.MRT1L is also available in Cut Tape (CT) packaging with 2,400 pieces in stock, suitable for lower-volume requirements.

Both substitute parts carry CSA, cURus, and TUV approvals, exceeding the original MQ 7TR certification scope (CE, CSA, cURus). Both are ROHS3 compliant, meeting current environmental compliance standards. The minor dimensional variation (0.110" diameter vs. 0.125" diameter) and DC cold resistance difference (0.0107 Ohms vs. 0.012 Ohms) remain within acceptable operational parameters for board mount through-hole applications.

Frequently Asked Questions (FAQ)

Q: Can 0251007.NRT1L and 0251007.MRT1L be used interchangeably with MQ 7TR?

A: Yes. Both parts meet all electrical and mechanical substitution criteria: identical current rating (7A), voltage ratings (125VAC/VDC), response time (Fast Blow), breaking capacity (50A AC, 300A DC), and operating temperature range (-55°C ~ 125°C). Physical dimensions vary slightly, but both are compatible with through-hole board mount applications.

Q: What is the difference between 0251007.NRT1L and 0251007.MRT1L?

A: Both parts are electrically and mechanically identical. The primary difference is packaging format and inventory availability. 0251007.NRT1L has significantly higher stock (175,060 pcs), while 0251007.MRT1L has lower availability (2,400 pcs). Both are supplied in Cut Tape (CT) packaging.

Q: Are the substitute parts RoHS compliant?

A: Yes. Both 0251007.NRT1L and 0251007.MRT1L are ROHS3 compliant, meeting current environmental regulations. The original MQ 7TR RoHS status was not specified.

Q: Do the substitute parts have better certifications than the original MQ 7TR?

A: The substitute parts carry expanded approval agency certifications. MQ 7TR holds CE, CSA, and cURus approvals. Both Littelfuse substitutes hold CSA, cURus, and TUV approvals, providing additional third-party validation.

Q: Will the smaller diameter of the substitute parts (0.110" vs. 0.125") affect board mount compatibility?

A: No. Both substitute parts maintain the same axial package configuration and 0.280" length, ensuring compatibility with through-hole board mount footprints designed for the MQ 7TR. The diameter reduction does not impact electrical performance or mechanical fit in standard fuse holder applications.

Q: What is the significance of the Melting I²t difference (8 vs. 10.4)?

A: The Melting I²t value indicates thermal energy required to melt the fuse element. The substitute parts have a slightly higher value (10.4 vs. 8), which remains within acceptable operational parameters for 7A fast-blow fuses at 125V ratings. This variation does not affect substitution validity for equivalent circuit protection.

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