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Techs: What's on your Shelf of Weird Things?

Discussion in 'Electronic Repair' started by Matt J. McCullar, Jun 16, 2007.

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  1. I imagine that any bench tech who's been fixing electronic stuff for a while
    has at least a couple of components housed on what I call The Shelf of Weird
    Things: items that caused a very bizarre problem, or look strange, or
    whatever.

    Here are a few things from mine:

    * A three-legged resistor. It used to be two separate power resistors, but
    one got so hot it exploded and fused itself into the identical resistor
    immediately next to it on the circuit board. It looks like a letter "Y" and
    even close inspection makes one suspect it was actually manufactured this
    way.

    * A 7805 voltage regulator that works as long as the input voltage is from 8
    to 12 volts, but when it goes any higher than that, the output voltage drops
    to about 3 volts.

    * A 1-watt carbon resistor that's missing a 1-mm wide band of carbon,
    exposing the internal element. Looks like it was lasered neatly out.
    Resistor still tests good, though.

    * A 1N4001 diode with the cathode marking on the wrong end.

    * Transistors with the wrong part numbers printed on them! (Took us a
    LOOOONG time to figure this one out!)


    Others I've heard about:

    * Multimeter test leads that accidentally carried too much current through
    them, instantly fusing the internal wires into one big, solid mass. Some
    tech was trying to measure the high voltage on a laser power supply but
    forgot to switch the meter from "Ohms" to "Volts." Now he's got a fried
    meter and red and black coathangers.
     
  2. b

    b Guest

    On a related note, i've got a collection of stuff retrieved from
    inside vcrs.
    toys, straws, audio c60s, coins , etc.

    and evidence of botched 'repairs', like the line transformer with
    charred arc holes in, someone had stuck chewing gum and sellotape over
    in an attempt to 'fix'.

    will think about what else i have and post back!

    -B
     
  3. Meat Plow

    Meat Plow Guest

    <snipped for brevity>

    I have some microwave stuff from Western Electric that not too many would
    even know which end was which or even be able to take a decent guess as to
    what it did. Hell I don't even know and I've had this crap for 20 years :)
     
  4. JANA

    JANA Guest

    More so than having weird technical problems, try evaluating some of the
    customers! Some of them have the wildest stories about their TV or
    themselves.

    --

    JANA
    _____


    I imagine that any bench tech who's been fixing electronic stuff for a while
    has at least a couple of components housed on what I call The Shelf of Weird
    Things: items that caused a very bizarre problem, or look strange, or
    whatever.

    Here are a few things from mine:

    * A three-legged resistor. It used to be two separate power resistors, but
    one got so hot it exploded and fused itself into the identical resistor
    immediately next to it on the circuit board. It looks like a letter "Y" and
    even close inspection makes one suspect it was actually manufactured this
    way.

    * A 7805 voltage regulator that works as long as the input voltage is from 8
    to 12 volts, but when it goes any higher than that, the output voltage drops
    to about 3 volts.

    * A 1-watt carbon resistor that's missing a 1-mm wide band of carbon,
    exposing the internal element. Looks like it was lasered neatly out.
    Resistor still tests good, though.

    * A 1N4001 diode with the cathode marking on the wrong end.

    * Transistors with the wrong part numbers printed on them! (Took us a
    LOOOONG time to figure this one out!)


    Others I've heard about:

    * Multimeter test leads that accidentally carried too much current through
    them, instantly fusing the internal wires into one big, solid mass. Some
    tech was trying to measure the high voltage on a laser power supply but
    forgot to switch the meter from "Ohms" to "Volts." Now he's got a fried
    meter and red and black coathangers.
     
  5. Guest

  6. Bill Janssen

    Bill Janssen Guest

    Post some pictures. I bet someone on the list will know what you have.

    Bill K7NOM
     
  7. OK, here's one:

    http://repairfaq.cis.upenn.edu/Misc/sale/thing-1.jpg

    Inside, are two nested cylinders that are electrically insulated from
    the others, but attached to two of the pointy probes on the left via
    the two middle flanges.

    What is it? :)

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
  8. Pinballer

    Pinballer Guest

    heating element?


     
  9. Doubt it. Nothing between the cylinders except air. :)

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
  10. Meat Plow

    Meat Plow Guest

    Laser gizmo?
     
  11. Bill Janssen

    Bill Janssen Guest

  12. m kinsler

    m kinsler Guest

    http://repairfaq.cis.upenn.edu/Misc/sale/thing-1.jpg
    It looks like a shielded four-point probe for determining the sheet
    resistance of some soft material. If so, the shoulders on two of the
    probes would maintain a uniform penetration distance. I seem to
    recall that in such applications, two of the probes are connected
    across a voltage source in series with an ammeter and the other two
    are connected across a voltmeter. Presumably there'd be a connection
    to instrumentation cables.

    The only problem with this theory is that the finish on the device
    doesn't seem correct for this sort of a job.

    M Kinsler
     
  13. m kinsler

    m kinsler Guest

    Going back in my memory, I think I've actually seen something like
    this before, and now I think maybe that it's not a four-point probe,
    but some sort of RF antenna element. Those probes look awfully
    familiar somehow.

    This is an excellent exercise.

    M Kinsler
     
  14. Eeyore

    Eeyore Guest

    I reckon my best is a KT88 with a molten anode.

    Graham
     
  15. Ron(UK)

    Ron(UK) Guest

    Flux Capacitor?

    Ron(UK)
     
  16. Hopefully, it'll come to you while your sleeping. :) But I really
    do have no idea. I got it in a box of junk.

    http://repairfaq.cis.upenn.edu/Misc/sale/thing-1.jpg
    http://repairfaq.cis.upenn.edu/Misc/sale/thing-2.jpg

    Again, there's nothing inside besides two smaller nested cylinders,
    electrically insulated from the outer one with glass beads between
    the flanges.

    I rather like the idea of the probe, except there are only 3 electrically
    separate contacts and then how does one connect to it?
    :)

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
  17. jakdedert

    jakdedert Guest

    I still hang on to the pair of slip-joint pliers with which I tried to
    loosen a mains lug in a 100 amp disconnect box...live. If I open the
    pliers fully, one side of the jaw is a perfect fit for a certain size
    allen screw.

    One night at a gig, the house electrician left unexpectedly, holding
    150' feet of our '0' feeder cable captive. I had no way to shut off the
    power and the truck was fully loaded. I bade everyone give me plenty of
    room, put one hand in my pocket and attacked the problem with my handy
    slip-joints. I had all three hot legs disco'd and was going after the
    neutral when the slip-joints...slipped.

    I was ready, though and jumped back as soon as I felt them let go. It
    made a pretty spectacular ZZZAP! and blew the tool clean out of the box.
    They have a pretty nasty gash melted into the side that I use to
    remind me not to be stupid.

    I solved the problem by cutting the feeder where it came out of the box
    and left eight or ten inches behind.

    jak
     
  18. m kinsler

    m kinsler Guest

    I still hang on to the pair of slip-joint pliers with which I tried to
    The diagonal cutters on my pliers have a nice notch that I
    inadvertently fabricated when I cut through an energized line cord one
    fine day. It makes a nice wire-stripping notch.

    M Kinsler
     
  19. James Sweet

    James Sweet Guest

    Been there, done that. Shut off the circuit breaker, then cut the wire and
    POW! Oops, that wire snaked off to a different circuit! Breaker was now off
    though :)
     
  20. Bob Weiss

    Bob Weiss Guest

    I have a TIP-41 transistor that works perfectly until the package
    exceeds ~90 degrees F. Then the B-E junction goes open. Let it cool, and
    it works again. You can watch the junction open and close with the heat
    from your fingers. I assume a defective wirebond to the die is to blame.

    I also have a 6550 tube that lost negative grid bias while operating.
    The tube got so hot that the glass envelope melted and "sucked in" to
    touch the plate. :)

    Bob Weiss N2IXK
     
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