I previously purchased an ESR meter kit a while back for checking capacitors on things like LCD monitors, power supplies, etc. And it has served me very well, but unfortunately, I needed something that would measure inductance. And while you CAN do it with a function generator and oscilloscope, it’s just a pain to break out the pieces needed, power things up, etc. I wanted a simple meter for checking inductors/chokes (partially because I have a huge pile of unmarked inductors I got from a very kind neighbor), since older/larger ones usually aren’t marked at all. The one that most people point to for hobby/intermediate use is the DER DE-5000, which is found from various resellers on eBay, and is the OEM part for the IET DE-5000 (IET just calibrate it a bit better, and offer proof of calibration). After some looking, and time, I found an eBay seller selling the DER DE-5000 with the alligator clips, tweezers, and ground lead for $85 with free shipping (a good $40 less than anyone else) (which I’ve told people on the eevblog forums about this sale, and probably given the seller a good 10-15 sales).
Ever since I started doing LCD monitor, and G5 iMac repair, I’ve wanted/needed to pick up an ESR (Equivalent Series Resistance) meter. Electrolytic capacitors are the bain of pretty much all modern power supplies. Pretty much everything else in a modern power supply is invincible compared to the caps… and while I’ve been extremely lucky that every iMac and LCD monitor I’ve repaired had obviously bad capacitors (bulging), that isn’t always the case… which is where an ESR meter comes in.
I won’t get into ESR in general, but you can find info on wikipedia here, or on this site. But basically, as Electrolytic caps age, their ESR increases, and generally once it rises above it set point, the device it’s in will stop working. In many cases, you can tell when this happens due to bulging/leaking. But that isn’t always the case, and having a meter is a good idea. I purchased the Blue ESR kit made by AnaTek, based off a design by Bob Parker for $73 off eBay. The kit arrived in a standard box, and was well organized. In about an hour and a half of soldering, I had the unit up and going. Really all you need is a soldering iron, some flush cutters, and if you want to calibrate the battery low indicator, you’ll want a variable bench power supply. Other than that, it was a piece of cake. While hourly, it’s not worth the $20 saved to buy the kit, it was worth it to get the satisfaction of building a kit and having it work. The instructions are easy to follow, and the unit fired right up when I was done.
I’d highly recommend it if you spend time doing repairs. At some point I’ll buy the Blue Ring Tester kit as well, as it makes diagnosing bad transformers easier, but for now, I’ve probably spent enough on test gear for the time being.