General electronics repair tips

Today I wanted to give some general repair tips for electronics. I've previously mentioned the two most common reasons for failure are lead-free solder and bad capacitors.

Lead-Free Solder:

Unfortunately diagnosing lead-free solder is not easy. Probably the correct way is to investigate each and every solder joint on the circuit board. You could use a multimeter to check it electronically and/or a visual inspection using magnification. But this can be time consuming considering the number of solder joints on a board. Obviously the first step is to verify the board has lead-free solder. This can be done is several ways:

1. Visual appearance - lead-free solder has a flat or non-glossy appearance whereas leaded solder is shinny.


2. Age of the item - the older it is the less likely it is to have lead-free solder. Before the mid 2000s and it's probably more likely to be leaded, after the mid 2000s and it's more likely to be lead-free solder.


3. Symbols - look for lead-free symbols (like "RoHS") on either the board itself or the case. If you find this symbol it for sure has lead-free solder, but the absence of this symbol does not necessarily mean leaded solder.

IF the board uses lead-free solder and IF you can't find anything else wrong with it, then lead-free solder is likely the problem. But how do you fix it? I know the theory, although I don't speak from personal experience. Ultimately you need to remelt the solder to repair the cracks. So you need to subject all or part of the board to heat - up to 260 C (500 F). The official way to do this is using a hot air rework station. But this is a specialized tool that few people own. If you own a heat gun you can use that. You can even put the board in the oven, or if the board is one-sided you can put it onto a griddle. You need to heat the affected part of the board up to 260 C then back down. Too much heat will damage the board. Also, be aware some of the components on the board (like plastics) may burn, so you might need to cover them with foil to shield them from the heat.

Bad Capacitors:

A bad capacitor can be easier to identify and relatively easy to repair. Often times you can visually detect when a capacitor has failed. It may bulge on the top, even start to leak from the inside (see pictures below). Unfortunately not all bad caps bulge, so you may need a special cap tester. But if you see a bulging cap you know it's bad. Replacing a bad cap is fairly easy, all you need is a soldering iron and the replacement part. To get the replacement part you need to know two things, the rating and the voltage. These will be written on the side of the bad capacitor. For example 830uF 25V. This is 830 uF (or microfarads) at 25 volts. When you order replacement parts get the exact same farad number, as for the volts you can get the same or a little higher. You can try your local electronics shop (e.g. RadioShack), but I'll tell you right now the chances they will have exactly what you need are slim. Instead order online, digikey.com and mouser.com are both great sites specializing in these parts. And these replacement parts are cheap to. Cost depends on the rating of the capacitor, but each component will probably cost you less than a dollar. So you could replace all the capacitors in a piece of electronics for only a few dollars.

Both of these repair techniques work with solder and soldering tools like irons. I suggest you watch some of the videos on youtube by "CuriousInventor" - he has great tutorials.