GDC-125MA Equivalent & Substitute Parts Reference

Part Overview

The GDC-125MA is a 125 mA, 250 V AC/DC glass cartridge fuse manufactured by Eaton - Electronics Division. This slow-blow fuse element is designed for 5mm x 20mm holder applications and requires an external fuse holder for installation. The part maintains Active product status with 793 pieces in current inventory. Equivalent and substitute parts are identified to support procurement flexibility, supply chain continuity, and application-specific compliance requirements across multiple manufacturers and series designations.

Key Parameters

Parameter	Value
Current Rating	125 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	5mm x 20mm
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35A
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)

Substitute Part Grouping Explanation

Substitution eligibility for the GDC-125MA is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Current Rating: 125 mA (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Breaking Capacity @ Rated Voltage: 35A (exact match required)

All substitute parts listed meet these mandatory electrical and mechanical parameters. Secondary parameters including melting I²t, DC cold resistance, operating temperature range, and approval agencies vary by manufacturer and series but do not affect functional substitutability within the specified electrical envelope. Compliance certifications and RoHS status are provided for design validation and regulatory requirements specific to end-use applications.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Series	Current Rating (Amps)	Voltage Rating - AC	Response Time	Package / Case	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance (Ohms)	Approval Agency	Inventory (Pcs)
GDC-125MA	Eaton - Electronics Division	GDC	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.063	1.97	cURus, IMQ	793
BK/GMD-125-R	Eaton - Electronics Division	GMD	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.043	8.125	CSA, UL	1631
BK/S506-125-R	Eaton - Electronics Division	S506	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.063	1.97	BSI, CCC, CSA, IMQ, SEMKO, UR, VDE	1120
BK1/S506-125-R	Eaton - Electronics Division	S506	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.063	1.97	BSI, CCC, CSA, IMQ, SEMKO, UR, VDE	1978
S506-125-R	Eaton - Electronics Division	S506	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.063	1.97	BSI, CCC, CSA, IMQ, SEMKO, UR, VDE	985
0034.3108	SCHURTER Inc.	FST 5x20	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.064	Not Specified	CCC, cURus, VDE	2282
0034.3763	SCHURTER Inc.	FSL 5x20	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.161	Not Specified	cULus	1968
0034.5608.11	SCHURTER Inc.	SMD-FST	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.064	Not Specified	cURus, VDE	967
0218.125HXP	Littelfuse Inc.	218	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.1465	4.2	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE	1785
0218.125MXP	Littelfuse Inc.	218	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.1465	4.2	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE	19944
0218.125TXP	Littelfuse Inc.	218	0.125	250 V	Slow Blow	5mm x 20mm	35A	0.1465	4.2	CCC, CE, CSA, KC, SEMKO, UL, VDE	1241

Engineering Selection Recommendations

All listed substitute parts maintain Active product status and satisfy the mandatory electrical and mechanical parameters for direct substitution with the GDC-125MA. Selection among equivalent parts should be based on the following factors:

Compliance and Certification Requirements: The GDC-125MA carries cURus and IMQ approvals. Substitute parts from Eaton (BK/GMD-125-R, BK/S506-125-R, BK1/S506-125-R, S506-125-R) provide CSA, UL, and extended international certifications (BSI, CCC, SEMKO, UR, VDE). SCHURTER parts (0034.3108, 0034.3763, 0034.5608.11) offer cURus, VDE, and cULus certifications. Littelfuse parts (0218.125HXP, 0218.125MXP, 0218.125TXP) provide the broadest certification scope including CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE.

Inventory Availability: Littelfuse 0218.125MXP offers the highest inventory level at 19,944 pieces. SCHURTER 0034.3108 provides 2,282 pieces. Eaton S506 series variants (BK1/S506-125-R at 1,978 pieces and BK/S506-125-R at 1,120 pieces) support secondary sourcing.

Thermal Operating Range: SCHURTER and Littelfuse parts specify operating temperature ranges (-55°C to 125°C for most variants), while Eaton GDC and GMD series do not specify operating temperature limits. SCHURTER 0034.3763 operates within -40°C to 85°C.

RoHS and REACH Compliance: All substitute parts carry ROHS3 Compliant status and REACH Unaffected designation where specified, supporting environmental and regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can BK/GMD-125-R replace GDC-125MA in all applications?

A: BK/GMD-125-R meets all mandatory electrical and mechanical parameters (125 mA, 250 V AC, 5mm x 20mm, 35A breaking capacity, slow-blow response). However, the DC cold resistance differs (8.125 Ohms vs. 1.97 Ohms) and approval agencies vary (CSA, UL vs. cURus, IMQ). Verify that end-use application compliance requirements accept CSA and UL certifications.

Q: What is the difference between Eaton S506 variants (BK/S506-125-R, BK1/S506-125-R, S506-125-R)?

A: All three S506 variants are electrically and mechanically identical with matching current rating, voltage, package, breaking capacity, melting I²t (0.063), and DC cold resistance (1.97 Ohms). Inventory levels differ: BK1/S506-125-R (1,978 pcs), BK/S506-125-R (1,120 pcs), and S506-125-R (985 pcs). Selection may be based on availability and procurement lead time.

Q: Why do Littelfuse 218 series parts show higher melting I²t values (0.1465)?

A: Melting I²t is a thermal characteristic that does not affect functional substitutability within the specified electrical envelope. All parts maintain the same 125 mA current rating, 250 V voltage rating, and 35A breaking capacity. Melting I²t variation reflects internal element design differences between manufacturers but does not alter circuit protection performance at rated parameters.

Q: Are SCHURTER parts suitable for applications requiring UL certification?

A: SCHURTER 0034.3108 and 0034.5608.11 carry cURus certification (which includes UL recognition). SCHURTER 0034.3763 carries cULus certification. These certifications satisfy UL requirements. Littelfuse and Eaton parts with explicit UL approval provide alternative options if direct UL listing is mandated.

Q: Can I use 0218.125MXP (Littelfuse) as a drop-in replacement for GDC-125MA?

A: Yes. The 0218.125MXP meets all mandatory substitution criteria: 125 mA current rating, 250 V AC voltage, 5mm x 20mm package, 35A breaking capacity, and slow-blow response time. The part is mechanically and electrically compatible. Littelfuse 218 series carries comprehensive international certifications (CCC, CE, CSA, K-MARK, SEMKO, UL, VDE) and maintains the highest inventory availability (19,944 pieces).

Q: What is the significance of the different series designations (GDC, GMD, S506, FST, FSL, SMD-FST, 218)?

A: Series designations identify manufacturer product lines and internal design variants. All listed parts within each series maintain identical electrical and mechanical specifications for the 125 mA, 250 V rating. Series differences reflect manufacturing processes, approval pathways, and compliance certifications but do not affect functional interchangeability at rated parameters.

Q: Should I prioritize parts with specified operating temperature ranges?

A: Operating temperature range specification provides additional design margin documentation. SCHURTER and Littelfuse parts specify -55°C to 125°C (or -40°C to 85°C for FSL variant), while Eaton GDC and GMD series do not specify limits. If application operates outside standard ambient conditions, select parts with documented temperature specifications that encompass the required range.

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