Transistor Unstabilized Circuits

Wendy

Joined Mar 24, 2008
23,415
One of the reasons I hated those old style cases is exactly what you're fighting, the leads aren't clear.

Thing about ground, you have the basic concept, now just build on it. Remember what I said about AC power and RF electronics? Ground with respect to AC power cords is a safety feature, and is actually connected to the earth outside (which is where the word ground came from). A lot of the Wikipedia articles have good explinations on the concept.
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
Hobbyist

Are you saying that collector and emitter can't be in the same column or they will short?

Or are you saying the wire in question is not connected to the transistor but goes straight to ground?

For the former, that would have me really confused. Aren't collector and emitter meant to be connected to each other?

For the latter the wire goes into f17 which is directly below g17 which is the collector. The wire does not bypass the transistor, it is in column 17 row f. The transistor collector and emitter are also in column 17.

You may need to zoom to see it properly as the wire in question is a little twisted but definately goes into column 17.

I do think however, I have wired the circuit incorrect because I believe what I used to think is the collector terminal is actually the emitter.

I am hoping someone can read the ancient encrypted symbology on this pre-historic tranisister and tell me which symbol denotes the collector and emitter....???

PS.
If the former case is true, i.e. the collector and emitter should not be in the same column, could you please explain why? Thats how they are in circuit diagrams....
 
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Thread Starter

howartthou

Joined Apr 18, 2009
111
One of the reasons I hated those old style cases is exactly what you're fighting, the leads aren't clear.

Thing about ground, you have the basic concept, now just build on it. Remember what I said about AC power and RF electronics? Ground with respect to AC power cords is a safety feature, and is actually connected to the earth outside (which is where the word ground came from). A lot of the Wikipedia articles have good explinations on the concept.
Thanks for your patience Bill, I think I have it now. :)
 

hobbyist

Joined Aug 10, 2008
892
Hobbyist

The transistor collector and emitter are also in column 17.

....???
I did zoom in, please help me out then in understanding your breadboard.

Isn't the column column 17 have all 5 terminal holes connected together as one strip.

If you plug 2 transistor leads in column 17 aren't they connected together. All my breadboards have 5 holes per term. strip (column) and the columns are seperate from each other.

Why is the collector and the emitter in the same column but not the base lead..I'm still thinking that one lead should be in each column when it comes to connecting a transistor into the breadboard.

I'm not trying to be a nuisance but I just think it is not hooked up right.

Sorry if I'm wrong...
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
Hi Hobbyist

I am happy to keep discussing this until we have a mutual understanding.

On my breadboard the holes in a column are connected to each other.

So that means the collector and emitter are connected which leads me to think you are correct. They are shorted in this setup!

I owe you a big thank you for persisting here :)

I don't know why it did not occur to me. I should turn the transistor so the emitter and collector and base are all in separate columns!

Thanks again for picking me up on this! A short would have blown my ancient transistor.

Now all I need to do is find out which terminal on the transistor is collector and emitter.

Once I know that I will wire it up again and post the picture here.

Thanks!!
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
It is difficult to see since the wires are all black but I think the pot is wired correctly.
The collector and emitter of the transistor are shorted together and are both connected to ground.
Hi Audioguru!

Yes you are correct. You have pointed this out in your first post, and Hobbyist makes this point clearer to me further down in this thread!

I guess you are not "Audioguru" for nothing. I should have paid more attention to your comment about the transistor being wired to short.

Thanks for pointing it out twice, my lesson here is to read responses more carefully.

As I said to Hobbyist, I will post a new photo of the circuit as soon as I work out which transistor terminal is collector and which is emitter.

Thanks to you and Hobbyist for saving my POT!! :D
 

Audioguru

Joined Dec 20, 2007
11,248
Hobbyist

Are you saying that collector and emitter can't be in the same column or they will short?
A few days ago I said that the collector and emitter of the transistor are shorted together.

As shown on the schematic, the emitter connects to ground (0V) and the collector connects to the 1k resistor R1.

Why don't you use a modern transistor that has a good datasheet showing which pin is which?
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
A few days ago I said that the collector and emitter of the transistor are shorted together.

As shown on the schematic, the emitter connects to ground (0V) and the collector connects to the 1k resistor R1.

Why don't you use a modern transistor that has a good datasheet showing which pin is which?
Yep, Audioguru I will heed your words very carefully from now onwards (read my message to you above), I learned a lesson and you helped save my POT. Thanks again. :)

There are a series of experiements I have to do with this particular transistor. I believe they require a germanium transistor because it heats up faster than a silicon transistor, in fact it may take a long time to heat a silicon tranisistor...:rolleyes:
 

hobbyist

Joined Aug 10, 2008
892
Hi Hobbyist

I am happy to keep discussing this until we have a mutual understanding.

On my breadboard the holes in a column are connected to each other.

So that means the collector and emitter are connected which leads me to think you are correct. They are shorted in this setup!

I owe you a big thank you for persisting here :)

I don't know why it did not occur to me. I should turn the transistor so the emitter and collector and base are all in separate columns!

Thanks again for picking me up on this! A short would have blown my ancient transistor.

Now all I need to do is find out which terminal on the transistor is collector and emitter.

Once I know that I will wire it up again and post the picture here.

Thanks!!
Hi,
Your welcome..
Glad to be of help.
 

Audioguru

Joined Dec 20, 2007
11,248
With the transistor's collector shorted to its emitter, it would do nothing and would not be harmed.

A modern silicon transistor will heat exactly as much as the ancient germanium transistor and will also demonstrate that it conducts more current as it heats up.
Every datasheet for a silicon transistor shows that its base-emitter voltage and its current gain are affected by temperature.
 

hobbyist

Joined Aug 10, 2008
892
There's got to be a way to do a non destructive test to determine the terminals.

For instance an ohm meter or some sort of a very low current probe, couldn't you bias the base then place one of the other leads at a voltage above the base voltage then use a low current led setup, to hook to the emitter from grond and check brightness, and volt. drop at the led. record that data,

then switch the two leads and do the same test, if it is hooked up backwards then emitter is more positve than base then led could not light up. But if hooked up properly then emitter is lower than base so transistor can conduct.

If you use large enough resistors to limit the current...

Just suggestions to get the ball roling...
 

PRS

Joined Aug 24, 2008
989
Now that I see it again, it looks like the collector is hooked up to nothing and the wire that should have gone to the collector is hooked to the emitter.
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
Hi All

I appreciate the responses, I just need a little time to reconfigure the circuit and post it here as you have been a great help I actually don't have anymore questions for now - but will post the revised circuit soon and ask for feedback then.

Audioguru
I did not know that shorting the transmitter to the collector would not harm the transistor but I believe you anyway. You did point out that I could blow the POT.

I also agree both types of transistors are affected by temperature thats why they need to be stabalised with resistors etc, as you would already know. But I think the germanium will heat faster? I remember they have slight different behaviors with regard to heat...something to do with how hot they can get before they burn out...

Hobbyist
Yes! I remember there is a test you can do with an ohm meter. I also have a transistor testor on my multimeter! And I have a data sheet on all my parts that mey have info on the ancient symbols! One of these have to work. I will let you know soon.

Paul
Either way, the transistor leads (CBE) should each be in separate columns....
 

Thread Starter

howartthou

Joined Apr 18, 2009
111
Hi All
Finally found out the E B C of my ancient 2N2431 transistor. The attached picture shows if you look at the transistor from the bottom (i.e. the pins staring at you) you will notice the middle pin is offset from the other two (forming a triangle), so thats the Base.

The Base pin must be at the bottom when looking at it, so the Collector is on the left and the Emitter is on right.

See the photo to see what I mean.

I also tested it on my multimeter. It appears to be a PNP type measuring 200 hFE.

So I am off to wire it up again. Be back soon...
 

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howartthou

Joined Apr 18, 2009
111
Hi All (again)

Attached is my second attempt after a lot of good advice from all of you.

You will have to take my word for it that the Emitter is at column 17, Base is at 18 and Collector is at 19, becuase you can't possibly see it in the photo (also read previous message for how I worked this out).

I have also attached the circuit diagram again for convenience.

So, before I turn it on, can you please let me know if its right this time?

Thanks again everyone.
 

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