solder lifespan

Comments

• John

  January 2012 edited January 2012

  Good to hear about the successful repair! I have witnessed this phenomenon too, but I've never attempted the particular repair myself. I'm pretty bad a soldering, unfortunately.
  
  I'm not an expert at this, but the way I understand it, there is one potential issue. That chip is a microfuse, similar to any kind of fuse, in that it is there to protect hardware from being damaged. Instead of the hardware being damaged, the fuse blows. So if the soldering job is bypassing the chip and creating a connection around it, the backlight may work for now, but a surge or other problem may cause the unprotected hardware to be permanently damaged. It's hard to say if that kind of situation would ever occur, and the machine might very well be just fine for the rest of its lifetime.
  
  If you DIDN'T bypass the chip, and the chip is still connecting both ends of the solder trace and serving its protective function, then I would say you've restored the situation 100%, microfuse protection intact. But I have to wonder why the backlight went out in the first place if the microfuse is still good...perhaps microfuses can be zapped, and then they are once again good after the charge diffuses? I'm not really sure. I suppose the best solution would be to replace the microfuse, just to be safe. Or maybe the microfuse was never really blown, and you merely repaired a trace that had cracked?
  
  But generally I'd say, if it's working, leave it, especially with something that small, because it's easy to make mistakes, and a second attempt might not go as well as the first.
  
  Anyway, I don't know if that helps, but congrats again! Also, if you want expert advice on this subject, there is a guy on iFixit.com/answers named AB Cellars who really knows his stuff when it comes to soldering.
  
  John
• abcellars

  January 2012 edited January 2012

  From reading what you have written, I am not sure if you reattached a chip that had a bad solder joint or put solder to connect the ends of the fuse to bypass it. If you reattached it because of a bad solder joint then you are good to go. Bypassing a fuse can make something work, but not fix it - there is a difference. Fuses are there to protect the critical and expensive parts. The fuse in question is a 2A, 402 SMD package. Since the system uses 24v - 27v at the highest brightness a 32v rating or higher will work fine. Voltage is how fast electricity is flowing. Current/amperage is how much electricity is flowing or being drawn. Fuses are about limiting how much electricity is in a circuit, in this case 2A, and need to have a voltage rating higher than that of the circuit. The voltage rating of a component is the highest voltage it can handle and it will degrade/fail faster if rated at the actual voltage in the circuit.
• devitol

  January 2012

  Thanks for the info. Do you know anywhere that replaces chips this small? I don't think I'm qualified enough to replace. Let alone where to buy the chip.
  
  
• abcellars

  January 2012 edited January 2012

  I live in the US and do this kind of work. Any place that has a fine tip soldering iron and good optics, preferably a stereo microscope (knows how to properly use them both) can solder this in, without difficulty. The fuse can be acquired from: http://search.digikey.com/us/en/products/F0402E2R00FSTR/478-2857-1-ND/768557 or a number of other places, such as Mouser, Newark, Farnell, etc.. that specialize in electronic parts. If you decide to do this work yourself I would order 10 of them. Usually there is a price break there and shipping will be the major contributor to the total cost. For a part like this the shipping should be the same for 1 or 100 of them, from the types of sources I have named. Parts this small, you can almost count on dropping at least once if you aren't use to working with them. Depending on where you have dropped it, you may or may not find it again. Depending on why your fuse blew it may or may not blow again the first time you turn your laptop on or sometime in the future. I'd count on using 2 out of what you order and there is only a couple of USD difference between 2 and 10. You can save back some or all of the ones that remain in case of future need and/or sell some or all of what remains on eBay or similar selling forum to recoup some of your investment.
• devitol

  January 2012

  Thanks for the info. What's the best way to get in touch with you for solder work?
• John

  January 2012

  Just an FYI, this site has user-to-user messaging, so you can click on the Inbox at the top, and then click "Start A New Conversation" to send someone an e-mail.