antique matchbox circuit? wha? :-)

Discussion in 'General Electronics Chat' started by chrisbitz, May 6, 2009.

  1. chrisbitz

    Thread Starter New Member

    May 6, 2009
    2
    0
    I recently cleared out a deceased 96 Year-old relative's house, and found this bizzare item.

    It's built in a wooden matchbox, and has that really old cloth-covered wire.

    The transistors are both labelled MAT 100, and the red things (dunno if they're resistors or capacitors) are both labelled 5000 20%.

    There's space for a 1.5v AA battery.

    [​IMG][​IMG][​IMG]

    I can't imagine what it could be for, having a mono male jack on it. maybe it was a tone generator, that you plugged into a mic socket or something?

    I appreciate you can't see the other side, but the jack plug is so corroded, I think it would damage the box to turn the circuit over?

    Anyway, I was hoping someone here could figure out what it was?

    Many thanks!

    Chris.[​IMG]
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    I think it is indeed some kind of signal generator.
    I think it is build like a multivibrator.
    It will probably give a squarewave as output.
    The red things are 5000 pF capacitors.
    The MAT100 will be some transistors.

    Greetings,
    Bertus
     
  3. gryskop

    Member

    Mar 1, 2008
    26
    0
    From the amount of components there it looks like a simple astable multivibrator circuit. The collector resistors are the same value, the base resistors the same value and both caps the same as well
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    You are right gryskop.
    The transistors will be PNP types and the powersupply turned around.

    Greetings,
    Bertus
     
  5. chrisbitz

    Thread Starter New Member

    May 6, 2009
    2
    0
    Wow! Thanks very much for teh replies guys...

    umm, what's an astable multivibrator? What's it used for, and why might an old man have one? :)

    He was a bit of an engineer, and had loads of tools, but nothing like a soldering iron, solder or wires.... so I don't think he was an elecronics enthusiast... so maybe he bought it from a friend or something?

    Thanks very much for helping me with my family puzzle!

    Chris.
     
  6. gryskop

    Member

    Mar 1, 2008
    26
    0
  7. Darren Holdstock

    Active Member

    Feb 10, 2009
    262
    11
    That's really neat, hang on to that. Those 2-transistor astables were very popular in the 60s and 70s as crude but effective signal sources for basic diagnostics, especially of audio equipment. The 555 timer didn't appear until 1971, and it was initially expensive compared to the two transistor circuit. My father built a germanium PNP version too, as a signal injector. I still have it.

    There's a chance the one in the OP was built for testing musician-type equipment, judging by the 1/4" jack plug. It'd be interesting to turn it on to see what happens. I don't know if the battery polarity is marked, but if it isn't, then the way to tell is that only the emitters of the transistors are tied directly together, and that node is battery positive. There may be some DC bias on the output of your matchbox circuit, as there doesn't seem to be a cap for DC blocking.

    Your circuit will look a bit like the one on the right here, if you ignore the LEDs.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Could you put a ruler next to that picture? It looks like it takes a "AA" battery, but without a size comparison. I tend to go with the consensus, it was used as a tone generator.

    Square waves, such as multivibrators produce, were also useful for RF signal generators. Is it possible your relative was a HAM or into electronics.
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
  10. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    I have found this on the MAT100 transistor:

    [​IMG]

    Greetings,
    Bertus
     
Loading...