Are these variable capacitors?

Good morning all!

I've recently been going through a load of old "dud" electronics items seeing what bits & pieces I can salvage and re-use with future projects.
I was given this old radio, the speaker and case have been re-used but I was wondering what these components are that are shown in the picture. As a pure guess I think they're variable capacitors, but googling around I haven't had much success in confirming what they are. The name "Jeckson" is stamped on the tops and there are a few printed numbers on the sides of some of them.
I have also tried the Jeckson website but couldn't find individual components on their site.

So, I'll hand it over to you. Do you think you could help?

Have never seen capacitors in that style.
It is variable inductors / coils
Used to tune the MF amplifier


Hi, the Jeckson cans are indeed Inductors or more precisly transformer assemblies, the radio will be a superhet type.
So the transformers will be, Oscillator and Mixer coils, and intermediate frequency amplifier transformers.
The variable capacitor is the square clear assembly next to the coil with the Red adjusting slug.

Tom.... :slight_smile:

Thanks guys!

At least there's peeps on here who know what they're on about... unlike me! But it's a learning curve and I really appreciate the help!

I will have another question for you shortly... first to take some pics... different circuit.

No problem, good to see you are learning from these execises, glad to help.
Tom... :slight_smile:

I know I should put this next bit into another thread, but as you guys are here and have already been really helpful, I thought I would be cheeky and pick your brains some more....

This circuit is from one of those "rape alarms" you can buy... for some reason a rather eccentric female friend bought me one... if only a nymphomaniac female would come my way, I wouldn't pull the buzzer!!!!

Anyway I know what the other components are bar this mysterious black, 3 legged creature is (on the left of the pic, not the transistor in the middle). There are no markings anywhere on it. At first glance I thought it to be like an electrolytic cap (I'm not entirely electronics illiterate), I have googled 3 legged caps and they were once largely used in old guitar amps, particularly fenders. But is this one? And if you're feeling brave enough could you explain why the 3 legs?

Again thank you so much for your help and understanding.

I think it’s a transformer, with an open magnetic circuit and a common connection between primary and secondary, rather like a miniature ignition coil. Does the flat end look like a ferrite material, and is it magnetic?

Thanks for joining us dc42.

Well, it's certainly made of some form of magnetic material as it will happily stick to the magnets in my laptop lid (done with caution as to not crack the screen), but unless it produces a magnetic field when a charge is passed through it, it doesn't pick anything up or stick to anything else. It's relatively heavy for its size and the flat end has a "rough-ish" texture to it, a similar texture to that of the coating on the changeable tips of my digital soldering iron.

Can't we tell I'm a newbie hey?!

Getting it under the lamp and having a good look, it has some sort of clasp at either end with a small gap where it doesn't meet, along with 3 grooves that are about 1-2mm in width running just below the flat end at a slight angle... this is all under the black coating. I would try and take a pic but I don't think the camera will pick that up.

Does that help at all?

Thanks for your help! :slight_smile:

Well, it's certainly made of some form of magnetic material as it will happily stick to the magnets in my laptop lid

Definitely a transformer then. My guess is that the transformer primary, transistor, resistor and 10nF cap form an oscillator, and the secondary steps up the voltage to drive a piezo transducer, which is what makes the loud noise. Or the piezo is connected across the primary, and the secondary is the feedback winding for the oscillator.

You could disconnect it from the other components and measure the resistance between the pins. You may even be able to measure the resistance without disconnecting it (measure it both ways round, in case one of the transistor junctions conducts and gives you a false reading).

Hi guys, I’d agree with dc42, very simple but probably effective oscillator and driver for a piezo tranducer.
Some of these devices use audio tweeter units which are tuned units, get maximum output with not much to go wrong.

Tom… :slight_smile:

Side Note: the big square item in clear plastic (almost not shown at the top of the first picture) which is above the tunable transformers/coils colored red and yellow..,. is actually what a variable capacitor looks like... because that is what that is.


Thank you all so much for all your help.

It's nice to know that there's guys out there like you who are willing to help without getting obnoxious, arrogant or sarcastic about things.

You could disconnect it from the other components and measure the resistance between the pins.

dc42: I shall try that shortly. I'll post the readings if anyone is interested. First to grab some lunch!

Ok, done some readings.

On the board with the other components made no difference in the readings when off the board.

Taking center leg as shared/common leg I get the following readings:
Left leg: 0.120k
Right Leg: 0.05k

Taking one of the outer legs as common and measuring from there I get the following:
outer = 0.122k
inner = 0.119k

So it is a transformer, and either the centre leg or the right leg is the common connection.

Well I guess my parts collection is getting a little bigger!

Thanks for everyones help! I shall let you all have a relatively peaceful day!