Equivalent & Substitute Parts for 3SYT-S Yellow LED T-1 Through Hole

Part Overview

The 3SYT-S is a yellow LED indication component manufactured by Bivar Inc., featuring a 3mm T-1 through-hole package with clear lens transparency and 50mcd brightness rating at 2V forward voltage. This product is classified as obsolete, making identification of functionally equivalent substitute parts essential for ongoing design support and procurement continuity. The component operates at 20mA test current with a 30° viewing angle and 590nm peak wavelength, serving as a discrete indicator in electronic assemblies requiring yellow light emission.

Key Parameters

Parameter	3SYT-S Value
Manufacturer	Bivar Inc.
Color	Yellow
Lens Size	3mm, T-1
Lens Transparency	Clear
Lens Style	Round with Domed Top
Voltage - Forward (Vf) Typical	2V
Current - Test	20mA
Millicandela Rating	50mcd
Viewing Angle	30°
Wavelength - Peak	590nm
Mounting Type	Through Hole
Package / Case	Radial
Height (Max)	4.50mm
Moisture Sensitivity Level	1 (Unlimited)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the 3SYT-S are identified based on the following critical parameters that determine functional compatibility:

Primary Compatibility Criteria:

Color: Yellow
Mounting Type: Through Hole
Package / Case: Radial
Lens Size: 3mm or 3.0mm T-1 configuration
Voltage - Forward (Vf): 2V nominal operation
Current - Test: 10mA to 20mA range

Secondary Consideration Parameters:

Lens Transparency: Clear or Diffused (both acceptable for indication applications)
Lens Style: Round with Domed Top or Round with Flat Top
Millicandela Rating: 2.1mcd to 125mcd (brightness variation acceptable based on circuit design)
Viewing Angle: 30° to 120° (application-dependent)
Wavelength - Peak: 583nm to 591nm (yellow spectrum range)
Height (Max): 4.50mm to 7.00mm (PCB clearance dependent)

Substitutes are grouped into two categories: Direct Voltage Equivalents (2V operation) and Alternative Voltage Options (1.8V, 5V, 12V) for designs requiring voltage flexibility.

Parameter Comparison

Parameter	3SYT-S	264-7UYD/S530-A3	414-10UYD/S530-A3	LTL-4251	LTL-4251N	HLMP-1719	HLMP-1620
Manufacturer	Bivar Inc.	Everlight Electronics	Everlight Electronics	Lite-On Inc.	Lite-On Inc.	Broadcom Limited	Broadcom Limited
Color	Yellow	Yellow	Yellow	Yellow	Yellow	Yellow	Yellow
Lens Size	3mm, T-1	2.90mm Dia	3.00mm Dia	3mm, T-1	3mm, T-1	3mm, T-1	3mm, T-1
Lens Transparency	Clear	Diffused	Diffused	Diffused	Diffused	Diffused	Diffused
Lens Style	Round with Domed Top	Round with Domed Top	Round with Flat Top	Round with Domed Top	Round with Domed Top	Round with Domed Top	Round with Domed Top
Voltage - Forward (Vf) Typical	2V	2V	2V	2.1V	2.1V	1.8V	5V
Current - Test	20mA	20mA	20mA	10mA	10mA	2mA	10mA
Millicandela Rating	50mcd	125mcd	40mcd	8.7mcd	5.6mcd	2.1mcd	2.2mcd
Viewing Angle	30°	60°	120°	40°	60°	50°	60°
Wavelength - Peak	590nm	591nm	591nm	585nm	585nm	N/A	583nm
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	Radial	Radial	Radial	Radial	Radial	Radial	Radial
Height (Max)	4.50mm	6.20mm	7.00mm	6.55mm	5.85mm	6.35mm	6.35mm
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
RoHS Status	N/A	N/A	N/A	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct 2V Voltage Equivalents (Recommended Primary Substitutes):

The Everlight Electronics parts 264-7UYD/S530-A3 and 414-10UYD/S530-A3 operate at 2V forward voltage matching the 3SYT-S specification. Both are active products with current manufacturing status. The 264-7UYD/S530-A3 provides higher brightness (125mcd) with 60° viewing angle and diffused lens, suitable for applications requiring increased visibility. The 414-10UYD/S530-A3 offers 40mcd brightness with 120° wide viewing angle and flat-top lens style, accommodating designs with broader light distribution requirements. Both maintain through-hole radial mounting and 3mm T-1 package compatibility.

Lite-On LTL-4251 and LTL-4251N Series (2.1V Operation):

The LTL-4251 and LTL-4251N represent active alternatives with 2.1V forward voltage, within acceptable tolerance of the 2V specification. LTL-4251 delivers 8.7mcd at 40° viewing angle with 10mA test current. LTL-4251N provides 5.6mcd at 60° viewing angle, also at 10mA test current. Both feature ROHS3 compliance and T-1 3mm package configuration. Height specifications (6.55mm and 5.85mm respectively) require PCB clearance verification against the original 4.50mm maximum height.

Alternative Voltage Options (Conditional Substitutes):

Broadcom HLMP-1719 and HLMP-1719-A0002 operate at 1.8V forward voltage with 2.1mcd brightness and 2mA test current, suitable for low-power indicator applications. HLMP-1620 operates at 5V with 2.2mcd brightness and 10mA test current. HLMP-1621 operates at 12V with 2.2mcd brightness and 13mA test current. These alternatives require circuit redesign to accommodate different voltage and current specifications but maintain T-1 3mm through-hole radial package compatibility and ROHS3 compliance.

Compliance Considerations:

All recommended substitute parts carry ROHS3 compliance certification. The Lite-On LTL-4251 series indicates REACH Affected status, while LTL-4251N and all Broadcom parts show REACH Unaffected status. Procurement decisions should account for regulatory requirements specific to end-use applications and geographic markets.

Frequently Asked Questions (FAQ)

Q: Can the 264-7UYD/S530-A3 directly replace the 3SYT-S without circuit modification?

A: The 264-7UYD/S530-A3 operates at 2V forward voltage matching the 3SYT-S specification and maintains identical through-hole radial mounting and 3mm T-1 package configuration. However, the diffused lens transparency differs from the clear lens of the original part, and brightness is higher (125mcd vs. 50mcd). Circuit compatibility depends on whether the application can tolerate increased brightness and diffused light distribution. PCB clearance must accommodate the 6.20mm maximum height versus the original 4.50mm.

Q: What is the key difference between LTL-4251 and LTL-4251N?

A: Both parts operate at 2.1V forward voltage and 10mA test current with identical wavelength specifications (588nm dominant, 585nm peak). The primary differences are brightness rating (8.7mcd for LTL-4251 versus 5.6mcd for LTL-4251N) and viewing angle (40° versus 60°). LTL-4251N has a lower maximum height (5.85mm versus 6.55mm), providing better PCB clearance compatibility with the original 4.50mm specification. LTL-4251N shows REACH Unaffected status while LTL-4251 is REACH Affected.

Q: Can I use HLMP-1620 (5V) or HLMP-1621 (12V) as substitutes?

A: HLMP-1620 and HLMP-1621 require circuit redesign due to different forward voltage specifications (5V and 12V respectively versus 2V for the 3SYT-S). These parts are suitable only for applications where the power supply and current-limiting resistor can be modified to accommodate the higher voltage requirements. Both maintain T-1 3mm through-hole radial package compatibility and ROHS3 compliance. Brightness is significantly lower (2.2mcd) compared to the original 50mcd.

Q: What does "diffused" lens transparency mean compared to "clear"?

A: Clear lens transparency provides direct light transmission with minimal scattering, resulting in a focused beam with defined brightness hotspot. Diffused lens transparency scatters light across a wider area, reducing peak brightness intensity but improving visibility across broader viewing angles. The 3SYT-S features clear transparency with 30° viewing angle, while substitute parts with diffused lenses typically offer 60° to 120° viewing angles. Selection depends on whether the application requires focused or distributed light emission.

Q: Are all substitute parts ROHS3 compliant?

A: All listed substitute parts carry ROHS3 compliance certification. The original 3SYT-S does not specify RoHS status due to its obsolete classification. For new designs or procurement requiring regulatory compliance, all recommended substitutes meet ROHS3 requirements. Lite-On LTL-4251 indicates REACH Affected status, while LTL-4251N and all Broadcom parts show REACH Unaffected status. Verify specific regulatory requirements for your application and geographic market.

Q: What is the significance of the 30° viewing angle on the 3SYT-S?

A: The 30° viewing angle indicates a narrow, focused light beam suitable for applications requiring directional indication with minimal light scatter. This narrow angle, combined with 50mcd brightness and clear lens, produces a concentrated bright spot visible from a limited range of viewing positions. Substitute parts with wider viewing angles (60° to 120°) distribute light across broader areas, reducing peak brightness but improving visibility from multiple angles. Circuit design and mechanical mounting determine whether narrow or wide viewing angle is appropriate.

Q: Can I substitute based on millicandela rating alone?

A: No. While millicandela rating indicates brightness intensity, substitution requires matching multiple parameters: forward voltage (2V specification), mounting type (through-hole radial), package size (3mm T-1), and color (yellow). The 264-7UYD/S530-A3 has higher brightness (125mcd) but different lens transparency and height. The HLMP-1620 has lower brightness (2.2mcd) but requires 5V operation. Brightness alone does not determine compatibility; all electrical and mechanical parameters must align with circuit requirements.

Q: What packaging options are available for substitute parts?

A: Substitute parts are available in multiple packaging formats: Bulk (standard loose components), Tape & Reel (TR) for automated assembly, and Cut Tape (CT) for smaller quantities. The 264-7UYD/S530-A3 and HLMP-1620 are available in Bulk packaging. The 414-10UYD/S530-A3 is available in Tape & Reel format. HLMP-1719-A0002 is available in Cut Tape format. Packaging selection depends on production volume, assembly equipment capability, and procurement quantity requirements.

Q: How do I verify PCB clearance compatibility?

A: Compare maximum height specifications: the original 3SYT-S is 4.50mm maximum height. Substitute parts range from 5.85mm (LTL-4251N) to 7.00mm (414-10UYD/S530-A3). Measure available vertical clearance on your PCB above the component mounting location. If clearance is less than the substitute part's maximum height, mechanical interference will occur. Additionally, verify that the 3mm T-1 lens diameter fits within the PCB hole pattern and surrounding component spacing.

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