Another soldering question

Discussion in 'General Electronics Chat' started by Challenged101, Jan 27, 2016.

  1. Challenged101

    Thread Starter New Member

    Jan 27, 2016
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    My soldering skills have been confined to splicing wires and replacing a diode. After reviewing Youtube tutorials, I've decided to attempt to replace a burnt out lcd on the climate control unit of my car. I purchased a cheap variable temp soldering station from Fry's and am now struggling to practice desoldering on a old mother board. The iron has a real fine pencil tip tinned with .032 rosin core solder. Initially, I was able to desolder a few joints but now am unable to. I'll clean and tin the tip and try again and again. One tutorial suggested adding fresh solder to a troublesome joint but I can't get it to melt. Supposedly, the station is a 70w unit with a 392f-897f range. I focused a infrared thermometer on the tip and for some reason it registered cold. I tested the iron against some wire and registered in the 140f range with the station turned up to the max..Tested a 25w pencil iron with roughly the same results. I don't know if I have a equipment or technique issue.
    Thanks for any constructive suggestions.
     
  2. SLK001

    Well-Known Member

    Nov 29, 2011
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    I think your soldering iron has burned out. Take/send it back to Fry's.
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    If you press the bare solder end to the iron tip and it does not melt your iron is either set too low or has a problem.

    See if you can exchange it.
     
  4. Challenged101

    Thread Starter New Member

    Jan 27, 2016
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    I can tin the tip without issue but the moment I apply the tip to a soldered joint, nothing happens, it won't melt and neither will new solder dabbed on the joint.
     
  5. SLK001

    Well-Known Member

    Nov 29, 2011
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    Intermittent contact in the heater circuit. Return for exchange.
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Motherboards are particularly difficult to solder and desolder because they have multiple layers that sink away the heat from your iron tip quickly. It's often necessary to use a preheater under the board. Your iron may not be working correctly but you chose a challenging practice medium. ;)
     
    Roderick Young likes this.
  7. Challenged101

    Thread Starter New Member

    Jan 27, 2016
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    Thank you KJ for your reply. I just picked up a 60w digital station from RadioShack and am still having no success no matter how high I set the temp. It is gratifying to know that the problem is probably my source of material rather than technique. Will a board out of a tv be easier to work with?
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Probably. It depends on the construction and layout. By the way, an infrared thermometer will read very low when aimed at a reflective target so unless you can figure out a way to make flat black solder, it won't be useful there.
     
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Or you adjust its emissivity value.. Most IR's have that setting for anything other than a perfect black body..
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Its still a skill/technique that you just haven't acquired yet :p
     
  11. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Make sure you have a large enough tip and a good amount of solder to act as a thermal bridge to the lead/pad junction you're trying to heat.
     
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