December 9, 2010

Retinning soldering iron tips

I use cheep 30w Radio Shack soldering irons. They work reasonably well for most soldering. The only problem is that their tips are junk. They don't stay tinned properly and before you know it only half of your tip is tinned. I'm in a perpetual state of broke so i didn't want to wast my money on a new tips for my irons. I just used them until there was almost no tinning left on them and I had to hold it at just the right angle to solder anything. 
Before retinning
I know that an iron could be retinned with tinning junk you can buy but that cost the same as the price of the tips i didn't want to buy. Besides I figured that I could tin it with normal solder if I cleaned the tip first. The ends of these irons where so caked with baked on junk that they where going to need some serous cleaning. They where also pitted in spots so I thought I could solve that problem at the same time. I chucked them in my drill and filed the old tinning and junk off the tips with a nail file. Next I reshaped them with a mettle file. This left them ruff and dull looking so I used steel wool and the drill at top speed to smooth the tips out until they where a shiny. Now the tips just needed to be tinned now so I reinstalled them into the irons and plugged them in. The copper surface of the iron worked better for transferring heat then the tinned surface so they heated up almost instantly. All I had to do to finish the project was completely cover the end of the iron in solder and wipe of the extra solder on a damp paper towel. Now the tips are better formed then they where new and the tinning is as good as new. 

After retinning. Its not the best pic my camera doesn't take micro photos well. 

December 8, 2010

Replacing Capacitors in a Motherboard.

     Last year I was given two computers. One of them worked fine but the other one started POST then splashed an error code and shut off. The code showed up and POST hit the kill switch almost simultaneously. It took an hour of restarting my computer righting down three of four digest and starting the computer again to get the entire code. After Googleing the error code I found a website that vaguely pointed to bad capacitors. After a closer inspection of my motherboard I confirmed that the caps where bulging. Scavenging through my junk box I discovered that I had every kind of capacitor possibly imagined except the 2500 pf  caps to replace the bad ones on the motherboard. I also have heard all kinds of stories about needing all kinds of specialized junk to work on motherboards like temp controlled soldering irons. all i had was the 20 year old 30 watt trash shack tinder box I annexed from my dads electrical box the year before. I wasn't letting any details like them stop me. So i rummaged through my box of junk some more and found another motherboard with 6000 pf caps. If I placed two of them in series i would end up with 3000 pf caps. Close to the 2500 pf i was looking for. There was also a 15 % tolerance to work in so i did some more math.
2500 + 15% = 2875
 (6000/2) - 15% = 2550 (Now that i think of it this should have bean 30% tolerance as the two tolerances would add together.)
After I finished the math I mumbled something about how close enough was good enough and decided to go on with the project.
I decided to take the caps of the donor bored first. I think thy must have used some kind of conductive glue instead of solder because it wasn't melting. I spent what seamed like hours bent over to board trying to get the solder to melt but it just sat there laughing in my face. I cracked after that hour and went for the heavy machinery; my rotary tool with a cut off wheel. I'm almost positive I was laughing maniacally as i slowly lowered the wheel to the board intent on cutting out the offending parts. It was probably because of this laughter that I inhaled all the dust from the Dremel in one big gulp causing me to have a coughing fit. Old motherboard 3 me zip (the third offence of the motherboard is a deferent story). I was about to through that cursed motherboard away in disgust at being thwarted once more by a peace of fiberglass. When the realization hit me that I could cut it too peaces with a pair of tin snips. Finally I would have my revenge on that board. It also got the capacitors off it to so it was win win i suppose. I ended up leaving the board on the bottom of the caps and just soldering wires onto the tag end of the lead that was still sticking out. Linking pairs of them together in series first.* Then I soldered leads onto the remaining tag ends to install into the board. Next I had to desolder the caps from the board I was working on. I was apprehensive at first because of my past experience with this posses but as I placed my iron on the first lead the solder melted almost before the iron hit it. all I had to do was push in the leads with the iron and the bad caps fell out. This was a huge relief i thought i was going to have to pull all the capacitors off the board by hand and solder to the exposed leads left behind.
 So I reassembled the computer and installed terned it on. It booted up on the first try. I later discovered that the on board Ethernet cart and sound card didn't work. So i added expansion cards for them. The computer worked for me for about a year before I no longer needed it and took it apart for other projects.

I do not recommend that you try repairing motherboards yourself it's a pain. This is simply to show how I solved a problem not to show you how you can do the same thing. I also don't recommend playing with electrolytic capacitors without knowing what your doing I've seen them blow up and it can be scary. I also never would have done this if I didn't have another computer to use as I might have killed the computer and all its parts.

*(Electrolytic  capacitors are linear so you have to use the right orientation or they will blow up.)