BK/ETF-1.25 Equivalent & Substitute Parts Reference

Part Overview

The BK/ETF-1.25 is a 1.25 A board mount radial fuse rated for 277 V AC, manufactured by Eaton - Electronics Division as part of the ETF series. This component is classified as obsolete, indicating that direct replacement with active production alternatives is necessary for new designs and ongoing procurement. The fuse features slow blow response characteristics and is designed for through-hole radial mounting in vertical orientation. Due to its obsolete status, equivalent substitute parts from active product lines must be evaluated based on electrical and mechanical compatibility parameters.

Substiute Parts

BK/ETF-1.25

Eaton - Electronics DivisionIn Stock: 1116BK/ETF-1.25 Datasheet

Current PartRFQ

SR-5-1.25A-BK

Eaton - Electronics DivisionIn Stock: 1113SR-5-1.25A-BK Datasheet

SimilarRFQ

0034.6616

SCHURTER Inc.In Stock: 52620034.6616 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BK/ETF-1.25 is determined by the following critical parameters:

Current Rating: All substitute parts must maintain the 1.25 A current rating to ensure proper circuit protection and prevent nuisance trips or inadequate protection.

Mounting Type & Package: All substitutes must be through-hole radial, can, vertical configuration to ensure mechanical compatibility with existing PCB layouts and footprints.

Response Time: Slow blow characteristic must be preserved to maintain compatibility with circuits designed for this fuse behavior.

Voltage Rating - AC: The primary constraint for substitution. The BK/ETF-1.25 operates at 277 V AC. Substitute parts with lower AC voltage ratings (250 V AC) may be used in applications where the actual operating voltage does not exceed the substitute's rating, but this represents a design downgrade and requires circuit analysis.

Approval Agencies: Substitutes must carry relevant safety certifications (UL, SEMKO, cULus, VDE, etc.) appropriate to the application's geographic and regulatory requirements.

The two identified substitute parts meet the core electrical and mechanical criteria but differ in voltage rating and breaking capacity specifications.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement in 277 V AC Circuits:

No perfect direct replacement exists among the provided substitute parts. Both SR-5-1.25A-BK and 0034.6616 are rated for 250 V AC maximum, which is below the original 277 V AC specification. Selection of either substitute requires circuit voltage analysis to confirm that actual operating voltage does not exceed 250 V AC.

SR-5-1.25A-BK Selection Criteria:

This Eaton part maintains manufacturer continuity and carries expanded international certifications (CCC, cULus, KC-MARK, PSE, SEMKO, VDE). It is RoHS Compliant and remains in active production. However, the reduced operating temperature range (-40°C ~ 85°C versus -55°C ~ 125°C) and lower breaking capacity (35 A versus 100 A) must be evaluated against application requirements. This part is suitable for applications operating within the reduced temperature range and where the lower breaking capacity is acceptable.

0034.6616 Selection Criteria:

This SCHURTER part offers the widest operating temperature range (-55°C ~ 125°C), matching the original specification. It includes explicit DC voltage rating (125 V DC) and higher breaking capacity for DC applications (50 A DC). ROHS3 compliance and REACH unaffected status provide regulatory advantages. This part is suitable for applications requiring the full temperature range and dual AC/DC voltage specifications.

Voltage Rating Consideration:

Both substitutes operate at 250 V AC. In applications where the circuit voltage is confirmed to remain below 250 V AC, either part is electrically compatible. In circuits designed for 277 V AC operation, substitution introduces a voltage margin reduction and requires engineering review.

Frequently Asked Questions (FAQ)

Q: Can SR-5-1.25A-BK be used as a direct replacement for BK/ETF-1.25?

A: SR-5-1.25A-BK matches the current rating (1.25 A), response time (slow blow), mounting type (through hole radial), and package configuration. However, the AC voltage rating is reduced from 277 V to 250 V. Substitution is permissible only if circuit analysis confirms that actual operating voltage does not exceed 250 V AC. The operating temperature range is also reduced (-40°C ~ 85°C versus -55°C ~ 125°C).

Q: Can 0034.6616 be used as a direct replacement for BK/ETF-1.25?

A: 0034.6616 matches the current rating (1.25 A), response time (slow blow), mounting type (through hole radial), package configuration, and operating temperature range (-55°C ~ 125°C). The AC voltage rating is reduced from 277 V to 250 V, requiring the same circuit voltage analysis as SR-5-1.25A-BK. This part additionally provides DC voltage rating (125 V DC) and higher DC breaking capacity (50 A DC).

Q: What is the significance of the breaking capacity difference between the main part (100 A) and substitutes (35 A AC)?

A: Breaking capacity defines the maximum fault current the fuse can safely interrupt without rupturing or creating a hazard. The main part BK/ETF-1.25 has 100 A breaking capacity, while both substitutes have 35 A breaking capacity. If the circuit's maximum fault current exceeds 35 A, the substitute fuses may not safely interrupt the fault. Circuit analysis must confirm that maximum available fault current does not exceed the substitute's breaking capacity rating.

Q: Why do the substitute parts have different physical dimensions?

A: SR-5-1.25A-BK measures 0.335" Dia x 0.319" H (8.50mm x 8.10mm), while 0034.6616 measures 0.335" Dia x 0.335" H (8.50mm x 8.50mm), compared to the original 0.329" Dia x 0.303" H (8.35mm x 7.70mm). These dimensional variations are within typical manufacturing tolerances for radial can fuses. PCB footprints designed for the original part must be verified to accommodate the slightly larger substitute dimensions, particularly the height dimension.

Q: What certifications should I prioritize when selecting a substitute?

A: Selection depends on the application's geographic and regulatory requirements. SR-5-1.25A-BK carries CCC, cULus, KC-MARK, PSE, SEMKO, and VDE certifications. 0034.6616 carries CCC, cURus, KC, PSE/JET, and VDE certifications. For North American applications, cULus or cURus certification is relevant. For European applications, VDE certification is relevant. For Asian markets, CCC, KC, and PSE certifications are relevant. Verify that the selected substitute carries certifications appropriate to your application's target markets.

Q: Is RoHS compliance a factor in selecting a substitute?

A: Both substitute parts carry RoHS compliance status (SR-5-1.25A-BK is RoHS Compliant; 0034.6616 is ROHS3 Compliant). If your application or end market requires RoHS compliance, both substitutes satisfy this requirement. The original BK/ETF-1.25 does not specify RoHS status.

Q: Can I use these substitutes interchangeably in the same circuit?

A: No. While both substitutes share the same current rating and response time, they differ in voltage rating, breaking capacity, operating temperature range, and physical dimensions. Selection must be based on specific circuit requirements. Once a substitute is selected and validated for a particular application, that specific part number should be used consistently.