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Confusing NPN transistor circuit

newbie102

New Member
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.Remote.JPG
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

Well-Known Member
Most Helpful Member
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
 

Nigel Goodwin

Super Moderator
Most Helpful Member
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?.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Here's an old schematic - interestingly I see it uses a PIC :D


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).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
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

Well-Known Member
Most Helpful Member
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.
 

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