Confusing NPN transistor circuit

[newbie102]

Hi everyone, I am newbie when it comes to electronics.
I am just wondering how this circuit works.

It is from a TV remote control.

The part that confuses me is that nothing is connected to the
emitter on T2 and T3 and nothing connected to the base on T1.

I just learned how to use eagle schematic, please bear with me.

 

[AnalogKid]

IF the three devices you are showing as bipolar transistors actually are (some could be FETs or diodes), then those pins are connected to something. Also, your pin assignments for the transistors might be incorrect; all transistors do not have the same pinout.

Are any of these components through-hole, or are they all surface-mount?

ak

 

[newbie102]

Thank you for responding. They are all surface mounted SOT-23.

 

[Nigel Goodwin]

I would say it's almost certainly drawn out completely wrong, TV remotes are extremely simple devices, with very little in them (other than a large chip that does everything), and assuming the devices in question are actually transistors they WILL have connections to the other terminals, but you might not be able to see them.

I would say it's unlikely to have three transistors in a TV remote - only one would be usual?.

 

[Diver300]

Thank you for responding. They are all surface mounted SOT-23.

I suspect that only T2 is a transistor. The others may be diodes in SOT-23 packages.

 

[Nigel Goodwin]

Here's an old schematic - interestingly I see it uses a PIC

**broken link removed**

This is a typical remote design, although usually the chip will be unidentifiable - the 455KHz resonator is pretty standard, and is a part that fails (they break off, due to people dropping the remote).

 

[newbie102]

Thanks everyone.
I replaced the two LED's and it worked.

 

[Nigel Goodwin]

Thanks everyone.
I replaced the two LED's and it worked.

IR LED's fail as well - so resonators, IR LED's, and the reservoir electrolytic capacitor (causes VERY short battery life) are all fairly common failures, and pretty well all you can change anyway.

Most remote failures though are due to abuse and damage (and cups of tea spilt on them!!).

 

[Diver300]

IR LED's fail as well - so resonators, IR LED's, and the reservoir electrolytic capacitor (causes VERY short battery life) are all fairly common failures, and pretty well all you can change anyway.

Most remote failures though are due to abuse and damage (and cups of tea spilt on them!!).

Ours fail most often by getting lost, but that's maybe a bit off-topic.

 

[Nigel Goodwin]

Ours fail most often by getting lost, but that's maybe a bit off-topic.

Well ones that got lost never made it to me for repair

There's also the 'eaten by the dog' issue as well!.

 

[Diver300]

There's also the 'eaten by the dog' issue as well!.

How did you know about my PICkit3 !!!!!!!!!!!