If you need to troubleshoot your computer, then you’ll need the right tools for the job. In this video, you’ll learn about multimeters, power supply testers, loopback plugs, and POST test cards.
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If you’re doing anything with hardware, you’re going to want a multimeter. But before you start poking around with power, make sure you know what you’re doing. You don’t want to run into any problems where you have electrocuted yourself accidentally. So be sure that you’ve trained and know exactly how to use these multimeters in your environment.
These multimeters do so much for us. They can measure voltage, and current, and resistance. You’ll sometimes see them referred to as a VOM. That stands for a Volt-ohm meter. There are analog versions, there’s digital versions, and all of them are pretty inexpensive.
The accuracy will vary widely, though. There are some multimeters you can buy for thousands of dollars, or you can buy one for less than $10. You just want to make sure that you have the right kind of multimeter for what you’re trying to do.
Whenever I’m looking at a multimeter, I want one that is very clear, relatively easy for me to use. I’m not looking for a huge amount of accuracy,and I think my multimeter, which is shown here, probably cost me about $20. And that’s about right for the type of work that I do with my computers and the type of things that I need from a multimeter.
Multimeters are great for checking things like AC voltage. That alternating current that’s coming right out of your connection in the wall can tell us what type of voltages we have to be seeing so we can validate that we’re getting exactly the right kind of power for the power supply that’s inside of our computer.
Once our power supply is converting things to direct current, we can check those voltages as well with our multimeter, check the motherboard, check to see if your CMOS battery has enough charge inside of it to maintain the configuration of your computer. All that can be done by checking the DC voltage.
Continuity checks to be useful as well. You can check fuses, you can check to be sure the cables are connected from one end to the other. Multimeters usually have also a beeping sound you can turn on, so not only are you seeing visual feedback on the multimeter display, you can listen, and when you hear the beeping noise, then you have continuity from one side of the circuit to the other.
The newest power supply testers are really easy to use. Most of them have this nice display on the front where I can plug in the power directly from my power supply. And then I can plug in other components into that same power supply as well, and it will give me statistics about voltages and information about what I happen to have plugged in and how much voltage it happens to be using.
This is so easy to use, I don’t have to stumble around with probes on a multimeter on all of the different connections. I simply plug in all of my components, and this will tell me everything.
If you’re working at all with network connections, or serial connections, or wide area network connections, then you might also want to have some loopback plugs available. These loopback plugs are used for testing physical ports, and they’re usually used in conjunction with a piece of software that will send information out the port and see if it is receiving information back in the receive side.
You’ll see these for serial ports, the RS-232, both the nine and some of the older 25 pin connections. For network connections, you’ll see loopback plugs for Ethernet or T1 or fiber type connections. Keep in mind these are not cross-over cables like you might see on the ethernet side of things. These are very specifically-built loopback cables the take everything coming out a transmit connection and send them back through the receive connection on that same device.
They look often like this– very simple, you have traffic coming in, you have traffic you’re sending right back out again. And you usually don’t need them unless there’s a problem. So it’s useful to keep them somewhere close to the hardware that you’re going to be using them with.
You might want to have different loopback ports or loopback cables for different types of media. You may need some for fiber, you may need some for copper, and you’re going to need exactly the right interface type for that loopback.
Just because it fits into an RJ-45 doesn’t mean it’s for Ethernet. It might be for a T1. So make sure you know exactly what they’re used for. And if you’d like to make your own, you can absolutely do that. Here’s a great website, spacehopper.org/5-in-1/ where you can make an ethernet cable, a crossover cable, a modem, a null modem, and a Cisco console cable, all from one series of adapters.
If we’re starting up our computer and we’re getting nothing from the start up, we may want to use one of these power on self test cards that will look at the power and give us some detailed error messages so that we can find out a little bit more about what might be going wrong with our hardware.