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Weller WTCPT tip not hot enough

Discussion in 'Electronic Repair' started by George Orwell, Aug 23, 2008.

  1. Eeyore

    Eeyore Guest

    Unlike me designing power amps where a similar slip tends to result in a lot of
    magic smoke being let out.

    Graham
     
  2. Eeyore

    Eeyore Guest

    Vibration is the killer with lead-free. Never mind the tin whiskers.

    But did you also know about tin pest ? I have no idea how much the temperature
    is affected by the copper (and silver for the rich) in lead-free but the Japs
    also use bismuth IIRC.

    " At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin
    transforms from the (silvery, ductile) allotrope of ?-modification white tin to
    brittle, ?-modification grey tin. Eventually it decomposes into powder, hence
    the name tin pest.

    The decomposition will catalyze itself, which is why the reaction seems to speed
    up once it starts; the mere presence of tin pest leads to more tin pest. Tin
    objects at low temperatures will simply disintegrate. "
    http://en.wikipedia.org/wiki/Tin_pest

    Graham
     
  3. N_Cook

    N_Cook Guest

    In the situation where you can just pull a component from a board, not
    desoledered, it is sometimes possible to see a grey powdery surface to the
    component, suggestive of tin-pest.

    And for using tin tinned new RoHS components destined for both old boards
    and Pb-Sn solder or new boards and silver solder, burr the tin off with a
    "diamond" cintride burr on a Dremmel, before tinning with the intended
    solder. A solid layer of tin is asking for trouble - turn to dust tin-pest.
     
  4. Eeyore

    Eeyore Guest

    These phase changes are called allotropes.

    No surprise. A guitar amp kept in the garage will see those temps.

    And whiskers.

    The military etc are doing an enhanced version of what you describe.

    Graham
     
  5. Eeyore

    Eeyore Guest

  6. Eeyore

    Eeyore Guest

  7. Eeyore

    Eeyore Guest

    How cold does the electronics in your car get in winter ?

    Graham
     
  8. N_Cook

    N_Cook Guest


    Do you know of a precise term, military or civil, for the process of
    mechanical (or other method) removal of full tin tinning of component legs,
    prior to use ?

    With that pic of tin-pested cap I should have said that the solder joints
    otherwise looked normal, only this surface layer tinning of the pin had
    transformed to grey.
     
  9. Arfa Daily

    Arfa Daily Guest

    Oh I had to work on them too ! Our company was responsible for background
    music machines that were rented out ro shops etc. They used a sort of
    cassette tape that was endless (!) in that it wound off the centre and back
    on to the outside. Bit like an 8 track mechanism, but only had four tracks,
    as I recall. Anyways, they had a bloody great amplifier built into them,
    based on 2N3055s. Being an early design, there was no protection or bias
    stabilization, and you only had to bring a 20k / volt meter near to some
    points to get them to run away, releasing their magic smoke ... Happy days.
    It's back when engineers learnt the business properly d:~}

    Arfa
     
  10. Arfa Daily

    Arfa Daily Guest

    No problem Jim, and it's nice to know that there are still people out there
    honest enough to admit to such a situation ! I would be interested to know
    what your friend's findings have been. If you once start working with
    lead-free, you won't mistake it for leaded again ! The first thing you will
    notice is why you suddenly don't seem able to make a shiny 'good' looking
    joint any more. The stuff is also a lot 'stiffer' as it comes off the reel.
    You might be surprised just how unpleasant the the stuff is to work with,
    compared to 'proper' solder - and that goes for the aggressive flux fumes as
    well. I wonder if your friend's place have put in additional bench
    extraction / ventilation to ensure that he doesn't breath the stuff ...

    Arfa
     
  11. Eeyore

    Eeyore Guest

    I see. I misunderstood that the first time you posted that pic.

    Quite possible, that seems to be the process.

    Graham
     
  12. Eeyore

    Eeyore Guest

    I don't myself but there must be one since there's a market for it.

    I followed.

    Graham
     
  13. Eeyore

    Eeyore Guest

    An, the days of 50uA meter movements. I do still have a small one and even found
    a leather BT case designed for it on the local market.

    Graham
     
  14. Eeyore

    Eeyore Guest

    I wonder just what we have waiting in store for us.

    I had considered applying to the Comission for exemption for all goods
    regularly subjected to vibration (such as used on location video and sound
    recording) and which also might be subjected to freezing temps in use or
    transit which could at least exempt pro A/V gear.

    It seems one (at least one) loudspeaker manufacturer successfully got an
    exemption on these grounds.

    Graham
     
  15. Arfa Daily

    Arfa Daily Guest

    My good old AVO 8 Mk IV, which was originally issued to me as an apprentice
    in about 1970, is still used every day. For 'resistance path' fault finding,
    and semiconductor junction basic proving, it is still my instrument of
    choice. There's something very comforting about seeing a needle swing over
    to 'about the right place'.

    I do of course have a raft of digital multimeters, both portable and bench,
    and a full array of digital capacitance and ESR and so on meters for more
    precise measurements where needed, but I find that a good quality analogue
    meter still fits the bill for much general service work.

    Arfa
     
  16. Arfa Daily

    Arfa Daily Guest


    I guess that just about covers almost all electronic gear then ! Lets just
    go for a complete ban on lead-free solder ! Power to the electronic
    engineering industry !!!!!

    Hmmmm. Video gear on location in freezing temperatures .... "So viewers,
    after a 2 hour descent, we see the first signs of the Titanic coming into
    view in remarkably sharp detail ... " Phhhttt !!! "Oh shit ..."
     
  17. Eeyore

    Eeyore Guest

    And it's horrid seeing the movement protection fail !

    I only really use it where the mechanical averaging is useful, such as noise
    measurements.

    Otherwise it's my trusty Fluke 77. I think I've only ever seen one 'go wrong'
    and it was repaired or replaced under warranty even though we didn't have the
    invoice because they track the serial numbers themselves.

    Graham
     
  18. Eeyore

    Eeyore Guest

    LOL !

    The freezing often occurs overnight in the truck. Never mind road quality for
    vibration getting it there.

    Graham
     
  19. Eeyore

    Eeyore Guest

    Is this a specific ruling you've come across ? Certainly interesting.

    Graham
     
  20. Hmmm...I used to be an apprentice at a company that manufactured
    background music machines utilising those big cartridges. They sounded
    bloody awful with violin music on - used to warble something chronic.
    For test purposes us young lads recorded stuff like Jimi Hendrix on
    them!

    Roy
     
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