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I have a SOT23-3 component marked CB RF (dash above F) as shown in the following images:

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I thoroughly searched both the web and a number of SMD code databases for information but I haven't been able to come up with anything.

Can you help me to identify the component?

I am assuming it is a switching mosfet as the PCB I'm repairing is a switch mode power supply and I've seen these switching mosfet's blow up before. You can see the component and surrounding it is blackened. I am still learning electronics so forgive me if I'm missing something obvious.

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    \$\begingroup\$ The focus / lighting of those picture is horrible. \$\endgroup\$
    – Rev
    Commented Nov 22, 2022 at 11:44
  • \$\begingroup\$ That's not SOT-23-3. Looks more like SOT-89. \$\endgroup\$
    – Hearth
    Commented Nov 22, 2022 at 14:44

2 Answers 2

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CB and RF... one of those is likely the part code, and the other ancillary data.

Package appears to be SOT-89 (TO-243, SC-62)

https://smd.yooneed.one/code4342.html shows several candidates for CB such as 2SD1368-B NPN transistor AF, 100V, 1A, 1W, B=160..300, 100MHz Same with RF: https://smd.yooneed.one/code5246.html

You'll likely have to deduce it further by reversing some of the circuitry surrounding it (i.e. is it really the primary switching device? If 24 VDC input, it could have a much lower voltage rating than if it were 240 VAC input, etc.)

And since this component failed, chances are high that something else has also failed. Expect more work to be needed - Q4 looks like it also got quite hot.

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Looks a lot like a 2SC4132 1.5A 120V NPN transistor, but no idea if that makes any sense in this context. It certainly could not be the output device in an off-line switcher.

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