Finding a Short?

[Sinnerx96]

Sorry to start a new thread, but this is somewhat of a separate issue, even though it might help my problem. I haven't seen much info about finding a short, here. You can read about my problem I'm having HERE
If you are interested.

I'm about to send my A12 module to SCA to have it looked at. But I figured that I'd take some time to go over this with a fine toothed comb before I do so. Could be a good learning experience for me, as I plan to build more SCA kits in the very near future.

Anyway,...How would I go about finding a short? I seam to have this feature on my DMM. It reads "Open", then Beeps and says "Short" when it finds a short. Where do I place the Negative Lead of the DMM, when placing the Positive lead on suspect joints? Ground?

Just out of curiosity, I placed the Negative Lead on Pin 4 of U1. Then by touching the Positive Lead on all the joints, I did find some shorts. What does this mean? Is this how I find a short? What can fix a short? A better solder joint?

Thanks in advance for anyone willing to help out a fellow electronics noob.

-Tony-

[dkatz42]

A short circuit is simply a connection where there shouldn't be one. This is usually due to sloppy soldering bridging adjacent pads together, though it can also be caused by uninsulated leads touching one another (pretty rare on circuit boards) or by a manufacturing flaw on the circuit board itself (also rare.)

The simplest way to look for shorts is to simply look at every solder joint on the board, making sure that each is clean, there isn't too much solder, etc. This is a fishing expedition.

The best way, given that you have an actual problem, is to take the schematics and knowledge of the circuit and examine the connections in the area of the circuit giving trouble, but there are relatively few of us qualified to take this approach.

Randomly connecting ohmmeter probes won't tell you anything useful. You'll see a "short" whenever you test across two things that are actually supposed to be connected (of which there are many.) The trick is finding connections that aren't supposed to be there.

If you're trying to find shorts this way, the two probes go between two points that ought to not have a direct connection. If you do the math, there are probably tens of thousands of combinations on the card, so this is clearly not a useful strategy.