GDB-125MA Equivalent & Substitute Parts

Part Overview

The GDB-125MA is a 125 mA fast-blow glass cartridge fuse rated for 250 V AC/DC operation in a 5mm x 20mm package form factor. This Eaton Electronics Division component requires a compatible fuse holder for installation and is currently in active product status with 981 pieces in stock. Glass cartridge fuses of this specification are widely used in industrial control circuits, consumer electronics, and power distribution applications where overcurrent protection is required. Substitute parts are identified to provide design flexibility, supply chain alternatives, and compatibility with various equipment specifications and regional compliance requirements.

Key Parameters

Parameter	Value	Criticality for Substitution
Current Rating	125 mA	Critical - Must Match Exactly
Voltage Rating (AC)	250 V	Critical - Must Match Exactly
Fuse Type	Cartridge, Glass	Critical - Must Match Exactly
Package / Case	5mm x 20mm	Critical - Must Match Exactly
Response Time	Fast Blow	Critical - Must Match Exactly
Mounting Type	Requires Holder	Critical - Must Match Exactly
Breaking Capacity @ Rated Voltage	35A minimum	Important - Must Meet or Exceed
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)	Critical - Must Match Exactly

Substitute Part Grouping Explanation

Substitution of the GDB-125MA is permissible only when all critical electrical and mechanical parameters are identical. The following parameters must match exactly across the main part and any substitute:

Current Rating: 125 mA
Voltage Rating (AC): 250 V
Fuse Type: Cartridge, Glass
Package / Case: 5mm x 20mm
Response Time: Fast Blow
Mounting Type: Requires Holder
Physical Dimensions: 0.205" Dia x 0.787" L

The Breaking Capacity at Rated Voltage must be equal to or greater than 35A. Secondary parameters such as DC Cold Resistance, Melting I²t, approval agencies, and RoHS compliance status do not prevent substitution but may be relevant for specific application requirements or regional regulatory compliance.

All identified substitute parts meet these critical requirements and are manufactured by Eaton Electronics Division, Littelfuse Inc., SCHURTER Inc., or OptiFuse, all established suppliers of fuse components.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Series	Current Rating (mA)	Voltage Rating (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Approval Agency	RoHS Status
GDB-125MA	Eaton - Electronics Division	GDB	125	250	Fast Blow	5x20mm	35	0.005	2.8	-	Not Specified
BK/GMA-125-R	Eaton - Electronics Division	GMA	125	250	Fast Blow	5x20mm	35	0.0024	4.895	CSA, PSE, UL	ROHS3 Compliant
BK/S500-125-R	Eaton - Electronics Division	S500	125	250	Fast Blow	5x20mm	35	0.005	2.8	-	ROHS3 Compliant
BK1/S500-125-R	Eaton - Electronics Division	S500	125	250	Fast Blow	5x20mm	35	0.005	2.8	-	RoHS Compliant
GMA-125-R	Eaton - Electronics Division	GMA	125	250	Fast Blow	5x20mm	35	0.0024	4.895	CSA, PSE, UL	ROHS3 Compliant
0034.1507	SCHURTER Inc.	FSF 5x20	125	250	Fast Blow	5x20mm	35	0.00484	Not Specified	CCC, cURus, VDE	ROHS3 Compliant
0217.125HXP	Littelfuse Inc.	217	125	250	Fast Blow	5x20mm	35	0.00478	3.82	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE	ROHS3 Compliant
0217.125TXP	Littelfuse Inc.	217	125	250	Fast Blow	5x20mm	35	0.00478	3.82	CCC, CE, CSA, KC, SEMKO, UL, VDE	ROHS3 Compliant
0235.125HXP	Littelfuse Inc.	235	125	250	Fast Blow	5x20mm	35	0.00273	5.75	CE, CSA, KC, UL	ROHS3 Compliant
0235.125MXP	Littelfuse Inc.	235	125	250	Fast Blow	5x20mm	35	0.00273	5.75	CE, CSA, KC, UL	ROHS3 Compliant
FSC-125MA	OptiFuse	FSC	125	250	Fast Blow	5x20mm	100	Not Specified	Not Specified	cULus, UL 248	ROHS3 Compliant

Engineering Selection Recommendations

All identified substitute parts are active products with confirmed inventory availability and meet the critical electrical and mechanical specifications required for direct substitution with the GDB-125MA.

Eaton Electronics Division Substitutes (Same Manufacturer):

BK/GMA-125-R, GMA-125-R, BK/S500-125-R, and BK1/S500-125-R maintain full compatibility with the GDB-125MA. The GMA series variants include CSA, PSE, and UL certifications. The S500 series variants provide ROHS3 compliance. These options are preferred when maintaining a single-manufacturer supply chain is a design requirement.

Littelfuse Inc. Substitutes:

0217.125HXP and 0217.125TXP (Series 217) provide comprehensive international approvals including CCC, CE, CSA, UL, VDE, and regional certifications (K-MARK, SEMKO, KC). These parts are suitable for applications requiring broad regulatory compliance across multiple markets.
0235.125HXP and 0235.125MXP (Series 235) provide CE, CSA, KC, and UL certifications with operating temperature range of -55°C to 125°C. These variants are appropriate for temperature-sensitive applications.

SCHURTER Inc. Substitute:

0034.1507 (FSF 5x20 series) provides CCC, cURus, and VDE certifications with operating temperature range of -55°C to 125°C, suitable for applications requiring European and Asian market compliance.

OptiFuse Substitute:

FSC-125MA provides cULus and UL 248 certifications with a higher breaking capacity of 100A at rated voltage, exceeding the 35A minimum requirement. This part is suitable for applications requiring enhanced fault current handling capability.

Selection among these substitutes should be based on specific application compliance requirements, regional regulatory mandates, and equipment design specifications rather than on electrical performance, as all parts are electrically equivalent.

Frequently Asked Questions (FAQ)

Q: Can the GDB-125MA be replaced with any of the listed substitute parts?

A: Yes. All listed substitute parts are direct electrical and mechanical equivalents. They share identical current ratings (125 mA), voltage ratings (250 V AC), fuse type (cartridge glass), package dimensions (5mm x 20mm), response time (fast blow), and mounting requirements. All meet or exceed the 35A breaking capacity specification.

Q: What is the difference between the Eaton GDB series and the Eaton GMA series?

A: Both series are 125 mA, 250 V AC/DC fast-blow glass cartridge fuses in 5mm x 20mm packages. The GMA series includes CSA, PSE, and UL certifications, while the GDB series does not specify approval agencies. The GMA series has a lower melting I²t value (0.0024 versus 0.005) and higher DC cold resistance (4.895 Ohms versus 2.8 Ohms).

Q: Are there differences in operating temperature ranges among the substitutes?

A: Yes. The GDB-125MA, BK/GMA-125-R, GMA-125-R, BK/S500-125-R, and BK1/S500-125-R do not specify operating temperature ranges. The Littelfuse 217 and 235 series, SCHURTER 0034.1507, and OptiFuse FSC-125MA all specify -55°C to 125°C operating range, with OptiFuse FSC-125MA limited to -55°C to 90°C. Applications requiring operation outside standard temperature ranges should specify parts with documented temperature ratings.

Q: What does "Fast Blow" response time mean?

A: Fast Blow indicates the fuse will open quickly when current exceeds the rated 125 mA threshold. All listed substitutes share this fast-blow characteristic, ensuring consistent overcurrent protection response across all equivalent parts.

Q: Can I use the FSC-125MA OptiFuse part if my equipment specifies GDB-125MA?

A: The FSC-125MA is electrically and mechanically equivalent to the GDB-125MA and will function identically in the same holder. However, the FSC-125MA has a higher breaking capacity (100A versus 35A), which may affect equipment certification or compliance documentation. Verify with equipment manufacturer specifications before substitution.

Q: What is the significance of the Melting I²t parameter?

A: Melting I²t describes the thermal energy required to melt the fuse element and is expressed in ampere-squared seconds. While all substitutes meet the 125 mA current rating, variations in Melting I²t (ranging from 0.00273 to 0.005 across the listed parts) reflect differences in fuse element design. These differences do not prevent substitution but may affect precise trip timing in sensitive applications.

Q: Are all substitute parts RoHS compliant?

A: All listed substitute parts are RoHS3 compliant or RoHS compliant. The GDB-125MA does not specify RoHS status. If RoHS compliance is a design requirement, select from BK/GMA-125-R, BK/S500-125-R, BK1/S500-125-R, GMA-125-R, 0034.1507, 0217.125HXP, 0217.125TXP, 0235.125HXP, 0235.125MXP, or FSC-125MA.

Q: Which substitute part has the broadest international certifications?

A: The Littelfuse 0217.125HXP includes CCC, CE, CSA, K-MARK, SEMKO, UL, and VDE certifications, providing the most comprehensive coverage for international markets including North America, Europe, and Asia-Pacific regions.

Q: Can I mix different substitute parts in the same equipment?

A: Yes, provided the equipment design does not specify a single part number. All listed substitutes are electrically and mechanically equivalent and will function identically. However, for consistency and traceability in production and maintenance, using a single part number across identical circuits is recommended.

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