ST-2-24 Equivalent & Substitute Parts Reference

Part Overview

The ST-2-24 is a laminated core power transformer manufactured by Signal Transformer, rated at 1.1VA with dual secondary windings capable of parallel (12V, 90mA) or series (24V, 45mA) output configurations. The primary winding accepts 115V input with 2500Vrms isolation. This through-hole mounted component is designed for PC pin termination and is currently in active production status with ROHS3 compliance.

Substitute parts are identified when equivalent electrical performance, mechanical compatibility, and regulatory compliance can be maintained across alternative manufacturers while preserving the core functional specifications of the transformer.

Key Parameters

Parameter	Value
Primary Voltage	115V
Secondary Voltage (Parallel)	12V
Secondary Voltage (Series)	24V
Output Current - Parallel	90mA
Output Current - Series	45mA
Power Rating	1.1VA
Core Type	Laminated
Primary Windings	Single
Secondary Windings	Dual
Center Tap	No
Mounting Type	Through Hole
Termination Style	PC Pin
Isolation Voltage	2500Vrms

Substitute Part Grouping Explanation

The 3FS-224 manufactured by Tamura qualifies as a direct substitute for the ST-2-24 based on the following critical parameters:

Identical primary voltage specification (115V)
Identical secondary voltage outputs in both parallel (12V) and series (24V) configurations
Identical output current ratings (90mA parallel, 45mA series)
Matching power rating (1.1VA)
Identical core type (Laminated)
Matching winding configuration (Single primary, Dual secondary, No center tap)
Identical mounting type (Through Hole) and termination style (PC Pin)
Equivalent isolation voltage (2500Vrms)

Physical dimensions show minor variations within acceptable tolerances for through-hole PCB mounting applications. Both components maintain equivalent regulatory compliance status.

Parameter Comparison

Parameter	ST-2-24 (Signal Transformer)	3FS-224 (Tamura)
Primary Voltage	115V	115V
Secondary Voltage - Parallel	12V	12V
Secondary Voltage - Series	24V	24V
Output Current - Parallel	90mA	90mA
Output Current - Series	45mA	45mA
Power - Max	1.1VA	1.1VA
Core Type	Laminated	Laminated
Primary Windings	Single	Single
Secondary Windings	Dual	Dual
Center Tap	No	No
Mounting Type	Through Hole	Through Hole
Termination Style	PC Pin	PC Pin
Isolation Voltage	2500Vrms	2500Vrms
Length	34.90mm	35.56mm
Width	28.60mm	31.00mm
Height - Seated (Max)	24.60mm	25.40mm
RoHS Status	ROHS3 Compliant	RoHS Compliant
ECCN	EAR99	EAR99
HTSUS	8504.31.4035	8504.31.4035

Engineering Selection Recommendations

Both the ST-2-24 and 3FS-224 maintain active product status and equivalent regulatory compliance. The ST-2-24 carries ROHS3 certification, while the 3FS-224 carries RoHS compliance. Both components are classified under identical ECCN (EAR99) and HTSUS codes, confirming equivalent export and tariff treatment.

Selection between these components should be based on:

PCB layout constraints: The 3FS-224 exhibits slightly larger footprint dimensions (35.56mm L × 31.00mm W × 25.40mm H) compared to the ST-2-24 (34.90mm L × 28.60mm W × 24.60mm H)
Supply chain availability: ST-2-24 inventory is 1024 pieces; 3FS-224 inventory is 1212 pieces
Packaging requirements: ST-2-24 is supplied in box packaging; 3FS-224 is supplied in tube packaging
Moisture sensitivity: 3FS-224 is rated MSL 1 (Unlimited); ST-2-24 is not applicable for MSL

Frequently Asked Questions (FAQ)

Q: Can the 3FS-224 be used as a direct replacement for the ST-2-24 in existing designs?

A: Yes. The 3FS-224 provides identical electrical specifications across all primary and secondary voltage/current parameters, matching core type, winding configuration, mounting type, and termination style. Physical dimensions show minor variations within acceptable tolerances for through-hole PCB applications.

Q: What are the key differences between these two transformers?

A: Electrical and functional specifications are equivalent. Physical differences include: length (34.90mm vs 35.56mm), width (28.60mm vs 31.00mm), and height (24.60mm vs 25.40mm). Packaging differs (box vs tube). RoHS certification levels differ (ROHS3 vs RoHS). Weight data is unavailable for the 3FS-224.

Q: Are there any compliance or regulatory differences?

A: Both components carry EAR99 ECCN classification and 8504.31.4035 HTSUS code. The ST-2-24 is ROHS3 compliant; the 3FS-224 is RoHS compliant. Both maintain equivalent export and tariff treatment.

Q: What should be considered when switching from ST-2-24 to 3FS-224?

A: Verify PCB layout accommodates the slightly larger footprint of the 3FS-224. Confirm packaging requirements align with procurement and assembly processes. Both components are through-hole mounted with PC pin termination, ensuring mechanical compatibility with existing PCB designs.

Q: Are isolation voltage and safety ratings identical?

A: Yes. Both transformers provide 2500Vrms isolation voltage, meeting equivalent safety and isolation requirements for the application.

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