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pull alarm help

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fairlight

New Member
I'm trying to reproduce a pull alarm from radio shack. I took it apart and followed the lines with the beep setting on the multimeter. The silicon black spot was scratched off with a razor blade. Unable to tell how it was connected inside there.

I think have got as far as possible for myself and need some assistance. What exactly is the bottom round thing with three connectors? I was thinking a capacitor of some sort. The red wire is bent and only connects to 21.

I also want to add another pull section, which was the main reason for disassembly.
The pull part is the rectangle on top.

Here are the pictures.
 

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dougy83

Well-Known Member
I'm trying to reproduce a pull alarm from radio shack. I took it apart and followed the lines with the beep setting on the multimeter. The silicon black spot was scratched off with a razor blade. Unable to tell how it was connected inside there.
That 'silicon black spot' was the IC that makes the beep signal.

I think have got as far as possible for myself and need some assistance. What exactly is the bottom round thing with three connectors? I was thinking a capacitor of some sort.
the black thing that looks like it has a coil of wire in it would be a transformer (if it has 3 wires), or an inductor (if it has 2 wires).

The red wire is bent and only connects to 21.
it connects to the 'pull switch' connector; when the string is pulled out, 21 is connected to the rest of the circuit and provides power for it to screech.
 

fairlight

New Member
I wonder if the IC can be substituted for a opamp chip or something?
It's probably impossible to find out the part number for the IC. Suitable replacement?

As for getting another pull trigger installed, I may try connecting wires to 12 and 14 to something, ground maybe? Then try another wire connected to 13 as the trigger wire.

Here is a picture of the whole alarm in case anyone recognizes it.
 

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