Equivalent & Substitute Parts for AP/ETF-125MA

Part Overview

The AP/ETF-125MA is a 125 mA, 277 V AC board mount radial fuse manufactured by Eaton - Electronics Division. This component is classified as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design support and procurement. The fuse features slow blow response characteristics and is designed for through-hole radial mounting in vertical orientation. Substitute parts must maintain electrical compatibility while meeting current manufacturing and compliance standards.

Substiute Parts

AP/ETF-125MA

Eaton - Electronics DivisionIn Stock: 1039AP/ETF-125MA Datasheet

Current PartRFQ

SR-5-125MA-AP

Eaton - Electronics DivisionIn Stock: 1086SR-5-125MA-AP Datasheet

SimilarRFQ

MRT 125-AMMO

Bel Fuse Inc.In Stock: 1036MRT 125-AMMO Datasheet

DirectRFQ

MRT 125-BULK

Bel Fuse Inc.In Stock: 1956MRT 125-BULK Datasheet

DirectRFQ

37201250411

Littelfuse Inc.In Stock: 387837201250411 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the AP/ETF-125MA is determined by the following criteria:

Primary Matching Parameters:

• Current Rating: 125 mA (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Package / Case: Radial, Can, Vertical (exact match required)
• Fuse Type: Board Mount (Cartridge Style Excluded) (exact match required)

Secondary Compatibility Parameters:

• Voltage Rating - AC: 250 V substitutes are acceptable for 277 V applications when breaking capacity and thermal characteristics are verified
• Physical Dimensions: Substitutes within 0.006" diameter and 0.016" height tolerance maintain board mount compatibility
• DC Cold Resistance: Range 1.35 - 1.6 Ohms acceptable

Substitute Classification:

Direct Substitutes (Identical Voltage Rating): None available in active status.

Compatible Substitutes (Reduced Voltage Rating): SR-5-125MA-AP, MRT 125-AMMO, MRT 125-BULK, and 37201250411 all operate at 250 V AC, which is lower than the original 277 V specification. These parts maintain identical current rating, response time, and mounting characteristics.

Parameter Comparison

Engineering Selection Recommendations

For 277 V AC Applications:

The AP/ETF-125MA operates at 277 V AC. All identified substitute parts operate at 250 V AC maximum. Selection of a 250 V rated fuse for a 277 V circuit represents a voltage derating condition. This substitution is not recommended for direct replacement in circuits designed for 277 V AC operation without circuit redesign or voltage reduction measures.

For 250 V AC Applications (If Circuit Voltage Permits Redesign):

Among the active substitutes, the following are recommended based on product status and compliance certifications:

MRT 125-AMMO and MRT 125-BULK (Bel Fuse Inc.):

• Active product status with extended production support
• Operating temperature range -55°C ~ 125°C matches original specification
• Breaking capacity of 50 A at rated voltage
• ROHS3 Compliant and REACH Unaffected
• AEC-Q200 certification provides automotive-grade reliability
• Identical physical dimensions to main part (0.329" Dia x 0.303" H)
• MRT 125-BULK offers bulk packaging for high-volume procurement

37201250411 (Littelfuse Inc., TR5® 372 Series):

• Active product status with established supply chain
• ROHS3 Compliant and REACH Unaffected
• Breaking capacity of 35 A at rated voltage
• Operating temperature range -40°C ~ 85°C (reduced from original -55°C ~ 125°C)
• Slightly larger physical dimensions (0.335" Dia x 0.315" H) require PCB layout verification

SR-5-125MA-AP (Eaton - Electronics Division):

• Active product status from original manufacturer
• Operating temperature range -40°C ~ 85°C (reduced from original -55°C ~ 125°C)
• Breaking capacity of 35 A at rated voltage
• ROHS Compliant
• Slightly larger physical dimensions (0.335" Dia x 0.319" H) require PCB layout verification

Frequently Asked Questions (FAQ)

Q: Can the AP/ETF-125MA be directly replaced with a 250 V rated substitute in a 277 V circuit?

A: No. The AP/ETF-125MA is rated for 277 V AC operation. All identified substitutes are rated for 250 V AC maximum. Direct substitution in a 277 V circuit would place the fuse in an overvoltage condition. Substitution is only appropriate if the circuit voltage is reduced to 250 V AC or lower, or if the circuit design is modified to accommodate the voltage difference.

Q: What are the physical compatibility considerations when substituting fuses?

A: The main part measures 0.329" diameter x 0.303" height. SR-5-125MA-AP and 37201250411 are slightly larger at 0.335" diameter x 0.319" and 0.315" height respectively. PCB footprint and mounting hole spacing must be verified before substitution. MRT 125-AMMO and MRT 125-BULK maintain identical dimensions to the original part.

Q: Which substitute offers the best thermal performance?

A: MRT 125-AMMO and MRT 125-BULK both support the full operating temperature range of -55°C ~ 125°C, matching the original AP/ETF-125MA specification. SR-5-125MA-AP and 37201250411 are limited to -40°C ~ 85°C. For applications requiring extended low-temperature operation below -40°C, the Bel Fuse MRT series is required.

Q: What is the difference between MRT 125-AMMO and MRT 125-BULK?

A: Both parts are electrically and mechanically identical. The difference is packaging: MRT 125-AMMO is supplied in Tape & Box (TB) format, while MRT 125-BULK is supplied in bulk packaging. Selection depends on procurement volume and assembly process requirements.

Q: Are all substitute parts RoHS compliant?

A: Yes. All identified substitutes are RoHS compliant. MRT 125-AMMO, MRT 125-BULK, and 37201250411 are ROHS3 Compliant. SR-5-125MA-AP is RoHS Compliant. The original AP/ETF-125MA RoHS status is not specified.

Q: Which substitute has the highest breaking capacity?

A: The original AP/ETF-125MA has a breaking capacity of 100 A at rated voltage. Among substitutes, MRT 125-AMMO and MRT 125-BULK offer 50 A breaking capacity. SR-5-125MA-AP and 37201250411 offer 35 A breaking capacity. For applications requiring high breaking capacity, the Bel Fuse MRT series is preferred.

Q: What certifications should I verify for my specific application?

A: Certification requirements depend on application standards. MRT 125-AMMO and MRT 125-BULK include AEC-Q200 certification for automotive applications. All substitutes include SEMKO and VDE certifications. Verify that the selected substitute meets all applicable industry and regional compliance requirements for your specific application.