Hi,
I need to repair a batch of an obsolete pcb.
It has a sot23-3 component marked 22NY.
Does somebody know which part is it?
It seems it is not a transistor nor a diode. Its reference is U while diodes and transistors on the same board are marked as D and Q. And I have read a lot of lists of transistor and diode marking.
I have made searches on the internet with no success.
This is all the information I have. Thanks!
search for “SMD marking codes”. You will find a number of websites. You can then search for 22NY within those databases.
There are several of those part-marking documents online, but I have had only about 50% success when using them to identify mystery parts.
Can you trace out enough circuit connections to guess the part’s function?
As you said, the “U” designation may be helpful. Opamps, microcontrollers, logic gates, and EEPROMS have been put into SOT-23 packages, but they all need more than 3 pins. The only common IC’s that come to mind in SOT23-3 are 3-terminal regulators, and functionally similar voltage references like the TL431.
So-called “bias resistor transistors” include integrated resistances to help set operating points. Some designers (or documentation controllers) might use these as an excuse to label the component a “U” rather than a “Q”.
Dale
If you can sketch the schematic diagram (the mystery device and maybe 20 parts surrounding it) then there is a possibility that I or someone else might be able to figure out what device would work. Often times an exact match might not be required.
So either infer a schematic diagram, or draw the parts on the board as they are, identify them as much as possible and draw connecting wires. I am assuming that the copper plating is only on one side or two sides?
That is similar to my argument.
I have what is now a 30 year old gas range which has electronic controls. I fixed the control board twice. I confess there was a fair amount of luck involved. Small electrolytic capacitors become open circuits with heat and time; I replaced 470 nF 50V with two 220 nF film types. The second failure was a TO92 darlington transistor with a corroded lead broken at the plastic body. Obsolete; I think I found only a basic description and not even a datasheet. But I kluged two bipolar transistors with two resistors and stuck it into the 3 holes; this also worked.
You should also look where it’s connected. For example if a pin is wired to a components VCC that SOT-23 could be an LDO Regulator. If connected to a MCU reset, it could be a supervisor. Also look for decoupling capacitors. It could lead to some ideas. Measure two pins forward and reverse (6 measurements) in Diode mode. This may give an idea that this is a common anode/cathode diode or some kind of BJT/FET.
Thanks to all.
I will send you in a private message the reversed schematic I have made.
Finally I have found the part:
stm1061
I have found the picture of the 3.4 threshold voltage instead of the 2.2V though.
Thanks again John, Dale, Bob and Murat.
Be careful.
If you’ve found a part with the same SMD marking, it is a strong indication, but no guarantee that it is the same part.
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