Partisan Repair – Part Three: Inductors, Relays and Contactors, by DN

See Part One – Resistors and Capacitors

See Part Two – Diodes and Transistors

Inductors

These you won’t find many bad. If you do it will look a open circuit. Sometime a transformer or motor will have winding that short together, but it maybe very unlikely to catch it with a multi-meter. So I am not going to mess with inductors. But you will find many bad relays and contractors, so lets go over that.

Relays & Contactors

These require applying power to the armature or the coil of the device to be tested. I am only working with low voltage in these photos. If you decide to play with live voltage I was not the one who told you to do it, in fact I told you not to play with live voltages. Also in this category are solenoids, you will find lots of bad ones in the right field.

So here you got a relay who’s contact is normally open. So it should look like an open circuit or a resistance of infinity ideally. So from the picture it so far looks good. The two red probes on the left are across the two contacts we are checking with the meter. The red one in the middle goes to the positive of a 24V power supply. Notice I do not have both leads connect to the armature that is required to energize it.

So here you got a relay who’s contact is normally open. So it should look like an open circuit or a resistance of infinity ideally. So from the picture it so far looks good. The two red probes on the left are across the two contacts we are checking with the meter. The red one in the middle goes to the positive of a 24V power supply. Notice I do not have both leads connect to the armature that is required to energize it.

Now I connected the other leg of the armature or coil to the 24V power supply (the black lead) and she turned on. My meter reads 51.8 Ohms. We want this to read as close to 0.0 as possible. If it were sealed I would throw it away and replace it, but good relays are serviceable and this is a good one!

POP the cover off!

Here are the tools to use to clean this. The one on the top is a type writer eraser, I think only Germany makes these anymore. The bottom is called burnishing tool Jonard tools makes good ones!

Now that set of contacts is to my liking!

This is not meant to be comprehensive by any means. There is a lot of other stuff I would have liked to prepare, but the truth is if you were at minimum putting these thing cover into practice, you would start figuring out the rest of it. I tried as time permitted to chose the most common things and the easiest thing to do. Typically things are easy; but also when things are hard, they are hard! Like anything else you have to actually do this for it to make sense and once you do try, you will see it is not that difficult.

Final Thoughts

When it comes to repairing one of the most critical skill to possess is getting good a de-soldering. Soldering is fairly easy with a good iron; but if you have junk equipment and are bad a de-soldering you will mess up a lot of stuff. Here is what you would want if starting out.

1) Soldering iron! There are two type, constant wattage (power) or constant temperature. Buy one with a constant temperature setting like the cool dial on the front.

2) Solder wick. Buy the stuff with rosin in it.

3) Flux

4) At minimum get a thing to slurp up the solder like a de-soldering vaccume pump or even the spring loaded pen type ones that are cheap. Whatever you can afford.

5) A good multi-meter. I would recommend anything made by Fluke. But at minimum you need one that is true RMS for AC circuits, and can test diodes, capacitors and resistors.

Depending on the level of interest I could go into testing chips, circuits, soldering/de-soldering and working with surface mount components? But there is enough here to get you going and I am sure I missed a lot of things I should have covered. Cool thing about getting into electronics, is it is a cheap initial investment and there is plenty of free broken electronics to practice on!