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Extending the life of a Tek 2465?

Discussion in 'Electronic Repair' started by DaveC, Nov 21, 2003.

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  1. als

    als Guest

    John beat me to it. :)
    Copper shim stock and copper water pipe is your friend
    for odd heat sink configurations. Especially if you need
    to make some convoluted shape to conform to the space.
    Clean it well.
    <als>
     
  2. Airy R. Bean

    Airy R. Bean Guest

    Copper water pipe is also your friend if you
    need a specially-shaped bit for your soldering-iron.
     
  3. DaveC

    DaveC Guest

    This sounds interesting... Photos?
     
  4. DaveC

    DaveC Guest

    I need something 2.5 mm (a little less than 0.1 inch) thick. I know I can
    layer more than 1 piece, but would like to reduce the thermal interfaces to
    just 2 (tab to shim; shim to heat sink).

    Do water pipe or other off-the-shelf copper come in such thick sections? (the
    US penny -- early production dates -- comes to mind...)

    Thanks,
     
  5. Layers would lose you a lot of thermal conductivity. For 2.5 mm sheet or
    bar, I'd try a non-ferrous metal scrap merchant. On a good day, they
    sell it by the pound; on a bad day by the carat.
     
  6. 3/32" (2.4mm) copper flats are a standard size (in 1/2" , 5/8", 3/4",
    1", 2" width, by whatever length). There are retail shops that sell
    this stuff, at a real premium in price, but you can buy just a small
    amount if that's what you need.

    Best regards,
    Spehro Pefhany
     
  7. DaveC

    DaveC Guest

    Would soldering the 2.5 mm copper shim to a copper heat sink increase the
    thermal conductivity? Or is thermal compound between the copper shim and an
    aluminum sink best? Or use an aluminum shim and an aluminum sink?

    Suggestions welcome.

    Thanks,
     
  8. DaveC

    DaveC Guest

    Is this otherwise known as "bar stock"?

    Thanks,
     
  9. Yes, one type of copper bar stock.

    Best regards,
    Spehro Pefhany
     
  10. Airy R. Bean wrote
    #10 or #12 solid wire (used for house mains wiring)
    is good for making "specialty tips" for your soldering
    gun. Very handy for scooping out custom-size/shape
    cavities in foam for storing small items (microphones,
    etc.)
     
  11. N. Thornton

    N. Thornton Guest

    Airy R. Bean wrote
    Call me hignorant but how are you going to make a slobbering iron bit
    out of water pipe?

    Regards, NT
     
  12. mike

    mike Guest

    I've been following this thread with interest.
    Had to check the header to make sure this wasn't
    rec.plumbing.
    I don't know whether to laugh or be sad.

    What's the first thing one should do when designing a heat sink
    for an unknown component?
    MEASURE THE TEMPERATURE OF THE DEVICE TO BE HEAT SINKED/SUNK!
    If anybody published that number for the chip in question, I missed it;
    Please repost. It would also be nice to have a second number with a
    known heat sink so we could estimate power/heat flow.

    Without numbers, we have no idea whether this is a fix
    for something that ain't broke. Yes, cooler is almost always better,
    but there is a thing called diminishing returns. Just opening the
    box and poking your screwdriver in there entails risk.

    Heat sinking is a network (often a series string) of (thermal) resistances.
    Do the math. It should be obvious from the materials and the
    temperature difference (see, this is where you need to know the
    temperature of the device) where the critical resistances are.

    There are reasons why virtually every heat sink on the planet is made
    from aluminum. Makes absolutely no sense to worry about the differences
    between aluminum and copper when you don't have any idea how much
    heat you need to remove...or when you're gonna put in a bunch of
    extra (bad thermal) interfaces. Typically, the first tiny bit of
    heat sinking makes a big difference. It's all downhill, asymptotically,
    from there.

    Just to throw gas on the confusion, anybody looked at putting in a
    small length of tubing to direct some air flow on the chip? But then
    we'd have to measure the temperature to see if it worked...and that
    ain't gonna happen. ;-(

    mike
    Did I mention that someone should measure the *#$%^& temperature????
    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  13. I read in sci.electronics.design that N. Thornton <>
    Cut a short piece longitudinally, flatten it and roll it up.
     
  14. DaveC

    DaveC Guest

    I (OP) am using something I call intuitive logic. Some like to call it
    SWAG'ing.

    This chip dies in this model scope. Frequently. It is considered a high
    failure component. There is *no* replacement for this component available
    from new sources, only scavenged ones. And expensive. All failures not caused
    by reckless use (ie, overvoltage, etc.) are thermal failures, whether short
    term or long term, IMO. Heat sinking -- *any* heat sinking -- is going to
    reduce the risk of failure.

    So even a non-scientific attempt, as long as the methods employed (proper
    materials, reasonable craftsmanship) are not sloppy, is going to improve the
    probability that my investment in this scope will be protected. At least more
    so than if I left it w/o a sink.

    Yes, measuring temperatures and calculating the size of the sink would give
    me the exact protection I need, but if I shoot for overkill and am reasonably
    confident that I've achieved this, there's no need for engineering a
    solution.

    A bit unscientific, maybe. But so what? SWAG is good enough for me, in this
    application.

    Not every solution *needs* to be scientifically calculated.
     
  15. mike

    mike Guest

    This is likely true for the part of the failure equation that involves
    heat at the point your're heat sinking. That ain't the only possible
    failure mode.
    I haven't heard ANY basis for this assumption.
    Taking it apart involves risk.
    Torquing on the screws and the resultant change in stress on the pins
    involves risk. What if I told you that the failure rate was due to
    moisture entering the package because the pins are thermally stressed
    cause the tab is bolted down?
    Yep, but every solution should have a *problem*.
    How do you know you're shooting for overkill when you don't
    even know which direction you're shooting? Confidence based on no
    data??


    So, you're saying you don't have any idea how hot it is and you don't
    care. That's sad for me 'cause now I have to take mine apart and
    measure the damned thing to determine whether I should have taken it apart.

    It's been interesting to watch this thread twist and turn based on
    absolutely ZERO, none, not any data. I mean, you've had the thing apart
    multiple times. Is it so hard to stick a thermocouple on it for
    a few seconds???

    I'll measure mine, but I'll keep the data a secret....

    Thanks, anyway,
    mike

    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  16. DaveC

    DaveC Guest

    Don't own a thermocouple. Don't know anyone who does. Is it worth it to rent
    one? Probably not. My judgement call. Maybe a bad one, maybe not.

    As to the possibility that failure is due to other modes, well there's
    nothing I can do to ameliorate those, but reducing the heat of the device
    could help reduce the possibility of failure in these modes. Heat could be a
    contributing factor.

    *Any* heat sinking will help this situation.
    I'm sorry to hear that. Not that I can't have your data; I don't feel the
    need to collect it or use any. SWAG is fine for me. I am sorry that you don't
    feel that you want to contribute to others that might be looking at this
    thread that might find your data useful , this being a public "help each
    other as best you can" forum.

    Good luck,
     
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