What are these parts: (S1A 72, W21 74)?

[jmb4370]

I have a circuit board I am trying to analyze and trace, and there are two components that I am sure are transistors, but I can't find any datasheets based on these markings (Google or otherwise). The are very small surface mounted rectangular devices, with 2 pins on one side, and a single pin on the other side. The markings on one are "S1A 72", and on the other is "W21 74". In each case, the last two numbers (72 and 74) are written sideways along the short side of the rectangle, while the other markings are written along the long side of the rectangle.

If anyone can direct me to a datasheet of these items, that would be most appreciated.

 

[Speakerguy]

S1A sounds like a diode, but I don't think they come in that type of package. It sounds like you have SOT-23 or SC-70 packaged devices.

 

[jmb4370]

That is just what I kept coming up with for the S1A 72, but both the S1A 72 and the W21 74 are in the same format with 3 pins like a transistor in the SOT-23 format, and the S1A 72 appears to be driving a relay from the output of an IC, so I am sure it is a transistor.

I just found an example of the component with a similar marking code, now to just find the two I am actually looking for, in case anyone knows how to find the specific manufacturer for these two items.

I can now also see the second item is actually W2F (not W21 as I first reported) with a manufacture date of April 2007, while the first item is indeed a s1A, manufactured Feb 2007.

 

[Speakerguy]

Diodes Inc uses markings like that on its transistors. Is there any sort of mfg mark at all? (doubt it on an SOT23 but worth asking).

 

[jmb4370]

The part numbers, and they are transistors, are s1A, and w2F. The numbers on the right side are indeed date codes. I heard back from an electronics supplier who said without knowing the manufacturer first, the specific item could not be determined. Even with a magnifiying glass, I can't see any manufacturer markings or symbols. They are likely just low power transistors, as one is connecting a small 5v relay to the output of an IC, while the other one is connecting the output of one IC to the input of another IC.

Any other suggestions besides removing the parts from the board to see if there are any markings on the underside?