BK/ETF-500MA Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The BK/ETF-500MA is a 500 mA, 277 V AC board mount fuse manufactured by Eaton - Electronics Division. This component is classified as Obsolete product status. 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 with active product status are necessary for new designs, production continuity, and long-term component availability.

Substiute Parts

BK/ETF-500MA

Eaton - Electronics DivisionIn Stock: 768BK/ETF-500MA Datasheet

Current PartRFQ

SR-5-500MA-BK

Eaton - Electronics DivisionIn Stock: 1117SR-5-500MA-BK Datasheet

SimilarRFQ

37205000411

Littelfuse Inc.In Stock: 1207137205000411 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the BK/ETF-500MA is determined by the following critical electrical and mechanical parameters:

Primary Matching Criteria:

• Current Rating: 500 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 Considerations:

• Voltage Rating - AC: The main part operates at 277 V AC. Substitute parts rated at 250 V AC are acceptable for applications where the circuit voltage does not exceed 250 V AC, as the lower voltage rating provides equivalent protection at reduced voltage levels.
• Size / Dimension: Physical dimensions must accommodate the PCB mounting footprint. Substitute parts with dimensions within ±0.006" (0.15mm) diameter and ±0.016" (0.40mm) height are mechanically compatible.
• Operating Temperature Range: Substitute parts must support the application's operating temperature requirements.
• Approval Agency: Substitute parts must carry relevant safety certifications (SEMKO, UL, cULus, VDE, CCC, KC-MARK) appropriate to the target market.

The identified substitute parts (SR-5-500MA-BK and 37205000411) match all primary criteria and are mechanically compatible. Both are active products with enhanced compliance certifications.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The BK/ETF-500MA is obsolete. Both substitute parts (SR-5-500MA-BK and 37205000411) carry active product status, ensuring long-term availability and continued manufacturing support.

Compliance and Certification: Both substitute parts exceed the certification requirements of the main part. SR-5-500MA-BK and 37205000411 carry expanded approval agencies (CCC, cULus/cURus, KC-MARK, SEMKO, VDE) compared to the main part (SEMKO, UL). Both substitute parts are ROHS3 compliant and REACH unaffected, meeting modern regulatory requirements.

Voltage Rating Application: The substitute parts are rated at 250 V AC, compared to the main part's 277 V AC rating. Selection between the main part and substitutes depends on circuit voltage:

• For circuits operating at or below 250 V AC: Either substitute part is suitable.
• For circuits operating above 250 V AC and up to 277 V AC: The main part BK/ETF-500MA is required if still available through inventory channels.

Mechanical Compatibility: Physical dimensions of substitute parts (0.335" Dia x 0.319" H for SR-5-500MA-BK; 0.335" Dia x 0.315" H for 37205000411) differ slightly from the main part (0.329" Dia x 0.303" H). These differences fall within acceptable mechanical tolerance for radial through hole mounting. PCB footprint verification is recommended prior to implementation.

Electrical Performance: Breaking capacity differs between the main part (100A) and substitutes (35A). Both substitute parts provide adequate protection for 500 mA circuits. Melting I²t values (2 for substitutes vs. 1.5 for main part) indicate slightly slower thermal response in substitutes, maintaining slow blow characteristics.

Temperature Range: The main part operates across -55°C ~ 125°C, while substitutes operate across -40°C ~ 85°C. For applications requiring extended low-temperature operation below -40°C or high-temperature operation above 85°C, the main part BK/ETF-500MA is required.

Recommended Selection: For new designs and production continuity: 37205000411 (Littelfuse TR5® 372 series) is recommended. This part offers active product status, comprehensive global certifications, superior DC cold resistance (0.155 Ohms), and established supply chain availability (11989 Pcs in stock).

For Eaton ecosystem preference: SR-5-500MA-BK provides equivalent functionality with active status and expanded certifications while maintaining manufacturer continuity.

Frequently Asked Questions (FAQ)

Q: Can SR-5-500MA-BK or 37205000411 directly replace BK/ETF-500MA in existing designs?

A: Direct replacement is possible for applications operating at 250 V AC or below. The substitute parts are mechanically compatible with standard radial through hole PCB footprints. However, applications requiring 277 V AC operation must retain the original BK/ETF-500MA or verify that circuit voltage does not exceed 250 V AC. PCB layout verification is recommended due to minor dimensional differences.

Q: What is the significance of the voltage rating difference (277 V vs. 250 V)?

A: Voltage rating indicates the maximum circuit voltage at which the fuse provides rated protection. A 250 V rated fuse is suitable for circuits operating at 250 V AC or lower. For circuits operating between 250 V AC and 277 V AC, the original 277 V rated part is required. Verify actual circuit voltage before selecting a substitute.

Q: Are the substitute parts certified for the same markets as the original?

A: The substitute parts carry expanded certifications. BK/ETF-500MA is certified by SEMKO and UL. SR-5-500MA-BK is certified by CCC, cULus, KC-MARK, SEMKO, and VDE. 37205000411 is certified by CCC, cURus, SEMKO, and VDE. Both substitutes meet or exceed the original certifications and support broader global market requirements.

Q: Do the substitute parts meet RoHS compliance?

A: Yes. Both SR-5-500MA-BK and 37205000411 are ROHS3 compliant and REACH unaffected. The original BK/ETF-500MA RoHS status is not specified in available documentation.

Q: What is the impact of different melting I²t values (1.5 vs. 2)?

A: Melting I²t describes the thermal energy required to melt the fuse element. The main part (1.5) melts slightly faster than the substitutes (2). Both maintain slow blow response characteristics. The difference is negligible for standard 500 mA circuit protection applications.

Q: Are there dimensional compatibility concerns with the substitute parts?

A: Substitute parts are slightly larger (0.335" Dia vs. 0.329" Dia; 0.319" H vs. 0.303" H for SR-5-500MA-BK). These differences are within standard PCB radial component tolerance. Verify that the PCB footprint accommodates the larger diameter and height before implementation.

Q: Which substitute part offers better long-term availability?

A: 37205000411 (Littelfuse) shows higher current inventory (11989 Pcs) compared to SR-5-500MA-BK (1071 Pcs). Littelfuse maintains established global distribution channels for the TR5® 372 series. For production continuity, 37205000411 is the preferred choice.

Q: Can the substitute parts operate in the full temperature range of the original (-55°C ~ 125°C)?

A: No. Substitute parts operate across -40°C ~ 85°C, which is narrower than the original (-55°C ~ 125°C). For applications requiring operation below -40°C or above 85°C, the original BK/ETF-500MA is required.

Q: What is the difference in DC cold resistance between the parts?

A: BK/ETF-500MA: 0.21 Ohms; SR-5-500MA-BK: 0.242 Ohms; 37205000411: 0.155 Ohms. Lower resistance reduces voltage drop across the fuse during normal operation. 37205000411 offers the lowest resistance, resulting in minimal circuit voltage loss.