Looking for unijunction transistors

[Kolloi]

I have a lot of old scrapped electronics items strewn about my place. I'm looking for unijunction transistors.. I know where I can buy them online but if I already have them in some kind of device then then I'd rather not buy them. Anyone have any ideas on what sort of devices might contain salvageable UJTs? Thanks

 

[Hero999]

Unijunction transistors are kind of obsolete; why do you want one?

 

[blueroomelectronics]

Unijunction transistors are kind of obsolete; why do you want one?

Unijunctions are often used for building time machines for getting back to 1976 when you could actually buy one. Sort of a paradox.

 

[audioguru]

COOL!
I found an old unijunction transistor.
How do I make a time machine so I can go back to the "dark ages"?

 

[blueroomelectronics]

I think the plans were part of a Radio Shack Science Fair kit. You also need a mercury switch & neon indicator bulb.
Unfortuneatly 1976 is a far back as it will go, the 1920 version needs a DeForest vaccum tube.

Ps don't drink the mercury.

 

[audioguru]

I had a mercury switch but its glass broke.
I had some old vacuum tubes but their glass also broke.
When I was a kid I plugged an NE-2 neon bulb into 120VAC and it dissappeared. I am lucky thet my hand and my vision also didn't disappear.

I dated my wife in 1976.

I wasn't born yet in 1920.

The mercury is in the water near Japan. That is why they walk funny.

 

[blueroomelectronics]

That's it an NE2, I've seen them used as colon on Nixie clocks

I did use a unijunction once I can't remember but I think it made a sawtooth wave. I liked it at the time but then the 555 was even more fun.

The 555 was / is the most popular IC ever made, if you can't buy one locally move.

 

[audioguru]

Do you remember the old PUT???
Programmable Unijunction Transistor.

 

[blueroomelectronics]

I recall it, barely. I think programmable means something with ones & zeros now.

Coffee ran out, fading fast sleepy time soon.

 

[Nigel Goodwin]

I have a lot of old scrapped electronics items strewn about my place. I'm looking for unijunction transistors.. I know where I can buy them online but if I already have them in some kind of device then then I'd rather not buy them. Anyone have any ideas on what sort of devices might contain salvageable UJTs? Thanks

The only units I've ever seen unijunction transistors in were some very old Grundig televisions, they were used as the frame oscillator device - it was something which failed, and I've probably still got some in stock somewhere?.

But as suggested, it's very old technology now.

 

[Hero999]

What do you want to do with your UJT?

I think think of at lest ten ways of achieving what a unijunction transistor does, ranging from a neon lamp to a PIC.

I used a unijunction transistor when I was a child too. I made a beeper using a piezo transducer as a timeing capacitor. This was back in the early 90s, I got the UJT from Tandy which them in a clearance sale. I remember the packaging being really dusty as they had probably been in the store since 1976 which was before I was born.

I've never seen a PUT before but I've heard about them on this forum.

 

[Kolloi]

Thanks for the replies. I want one in order to find out what this circuit sounds like:

https://www.aaroncake.net/circuits/torgan.asp

As 'transistor organs' are something of a cult classic of the 60s and 70s, in a sense I will be going back to 1976 . If on the other hand as one user said it just makes a basic saw wave, then that's less interesting but I might build it anyway, depending on whether I can get hold of a UJT. For some reason I keep imagining a theremin-like sound coming from a UJT oscillator...

 

[Kolloi]

[double post]

 

[Nigel Goodwin]

Thanks for the replies. I want one in order to find out what this circuit sounds like:

https://www.aaroncake.net/circuits/torgan.asp

As 'transistor organs' are something of a cult classic of the 60s and 70s, in a sense I will be going back to 1976 . If on the other hand as one user said it just makes a basic saw wave, then that's less interesting but I might build it anyway, depending on whether I can get hold of a UJT. For some reason I keep imagining a theremin-like sound coming from a UJT-based oscillator...

Just a basic sawtooth, most such 'organs' just used a normal two transistor multivibrator instead.

 

[Hero999]

If you build a 555 circuit the waveform on the capacitor is near-sawtooth shaped. You can easilly amplify it and drive a speaker using the LM386.

It isn't difficult to select different value resistors to change the frequency.

Another option would be to use a reverse bias oscillator, which is much simpler but the frequency is directly proportional to the battery voltage.
**broken link removed**
http://www.diy-electronic-projects.com/p184-Reverse-Bias-Oscillator

 

[Kolloi]

thanks Nigel and Hero

I think on balance if it's just a simple sawtooth then I can synthesise it easily enough with a computer and I needn't bother building a circuit.

 

[Hero999]

The only disadvantage with that is it isn't portable unless you use a PDA or mobile phone.

The reverse bias oscillator will cost nothing to make - you can get all the parts from an old radio which can be found at your local tip.

 

[audioguru]

The "transistor organ" has a sawtooth waveform at its timing capacitor but its output is short duration pulses which sound like a buzzer.

I think the pitch of the tones change as the battery voltage runs down.

 

[mvs sarma]

Philips device 2N2646 used to be popular those days and was extensively used for local time base in telecom power plants- like 48V 400A float rectifiers. Perhaps teat can be searched in the LOTs that you have access to.

 

[Kolloi]

Philips device 2N2646 used to be popular those days and was extensively used for local time base in telecom power plants- like 48V 400A float rectifiers. Perhaps teat can be searched in the LOTs that you have access to.

In the 'LOTs' I have access to??