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What is this thing?

E

ewag2

Well-Known Member
Premium Member
Hi, I was told that this is a Korean mine. Can anyone here positively identify what it is?

The body has a diameter of 5 inches and a height of about 2 3/4 inches. In metric it measures 127 mm diameter and about 70mm tall. (Depending on how tight the lid is screwed down.) The only exterior marking I can find is what looks like it might be a large "D" stamped into the lid where there also seems to be a large blue dot that is partially obscured. On the inside, the two loose wires from the copper coil look like they might have been attached at the two tiny holes in the circuit board. The only distinguishing features of the exterior of the body are visible in the pictures.
 

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Hi ewag2,from the looks of the writing and colour coding on the resistors it looks distinctly western,
Regards,
Don,
 
It could still be South Korean.

Electronic components in the west have standardised markings. I'm not sure about North Korea, but the South could have produced a pcb looking like that.

If you can post a picture of the writing on the capacitors there should be a date and manufacturer code on them.
 
An oscillating circuit of some description, manufactured post 1968. What are the markings on the transistor?

TimG
 
Maybe an anti detector device/mine? It explodes when a detector is sweeped over.
Regards, DJH
 
Glevum, The only writing I can see on the capacitors is "ARCO PM .0081+/-2% 100V"

Is the large silver rectangular thing held on with the two cable ties a capacitor also? It has no markings that I can see.
 
TimG, The markings on the transistor are "JAN2N918 E-CRP7422" . I'm almost certain that's what it says, though the markings are very tiny and I could have misread a digit.
 
ARCO is an US Company that manufactures capacitors.
The transistor is a 2N219. The 'JAN' prefix denotes that it conforms to US military standards.
The 'large silver rectangle thing' appears to be a crystal.

TimG
 
What is the box and the screw on lid made of? Plastic or steel . Thin walled , thick walled?
 
pzgr40 said:
What is the box and the screw on lid made of? Plastic or steel . Thin walled , thick walled?
Click to expand...

The box and lid are thick walled and made of plastic, with a rubber gasket between them. The plastic body and lid are very thick and durable. I think it's at least 1/4 inch thick.
 
Last edited:
TimG said:
ARCO is an US Company that manufactures capacitors.
The transistor is a 2N219. The 'JAN' prefix denotes that it conforms to US military standards.
The 'large silver rectangle thing' appears to be a crystal.

TimG
Click to expand...

Thanks TimG for this information. While I still don't know exactly what this thing is, this brings me closer to an answer. I was told it was Korean, but maybe that was because it is something the US used in South Korea or it is something we supplied to South Korea. I still hope to find out.
 
Andy, I don't think putting batteries in it to see what it does would be very prudent if it is of unknown origin...
 
OK then take it to an electronics guy and see if he can recognize the parts and what they would do in that configuration
 
A quick visual tracing of the circuit shows it's a very simple crystal oscillator. From the component values, the oscillation frequency of this circuit is likely to be around 120-150kHz.

The size and date of the crystal can suggests a low frequency crystal in the range 100-500kHz, and the inductance of the coil works out at 350 to 450 microhenry*. Given the capacitor values, the operating frequency comes out in the range 120-150kHz. The 2N918 was an excellent transistor for oscillators in the low frequency to VHF range.

Putting batteries in and reconnecting the coil won't produce any visible or audible results. An oscilloscope or low frequency spectrum analyser will indicate whether it still works. The radiated signal, in addition to the metal content of the components, would also most likely set off certain types of metal detector, which suggests the device might be for training.




Tom.


*For dimensions in inches, the inductance of a single-layer, air-cored coil is given by

L = {Radius[SUP]2 [/SUP]x Turns[SUP]2[/SUP]} / {9 x Radius + 10 x Length}
 
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Snufkin said:
A quick visual tracing of the circuit shows it's a very simple crystal oscillator. From the component values, the oscillation frequency of this circuit is likely to be around 120-150kHz.

The size and date of the crystal can suggests a low frequency crystal in the range 100-500kHz, and the inductance of the coil works out at 350 to 450 microhenry*. Given the capacitor values, the operating frequency comes out in the range 120-150kHz. The 2N918 was an excellent transistor for oscillators in the low frequency to VHF range.

Putting batteries in and reconnecting the coil won't produce any visible or audible results. An oscilloscope or low frequency spectrum analyser will indicate whether it still works. The radiated signal, in addition to the metal content of the components, would also most likely set off certain types of metal detector, which suggests the device might be for training.




Tom.


*For dimensions in inches, the inductance of a single-layer, air-cored coil is given by

L = {Radius[SUP]2 [/SUP]x Turns[SUP]2[/SUP]} / {9 x Radius + 10 x Length}
Click to expand...

Thank you Tom for this very interesting and detailed information. I look forward to finding out what kind of training device this is. Rob
 
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