To fix your computer, you’re going to need the right tools. In this video, you’ll learn about multimeters, power supply testers, loopback plugs, and POST cards.
One tool that you will use over, and over, and over again is a multimeter. Everyone should have a good multimeter. For instance, you can use it to check your AC voltages coming out of the wall. And make sure that you’re getting the right voltages that you would expect for your environment.
Multimeters can also be used to check to DC power of our computers. That’s the power that’s inside of our computer case coming from our power supplies. This is also useful to check the capacity of the batteries that we’re using.
And we can use our multimeters for continuity testing. We can look to see if there’s continuity across an individual wire, we can test fuses, and we can do an entire wire map. Where you can check the end of one cable interface, and check to see exactly what pins are connected between each other between both sides of the cable.
This is a good example of the different functions available in a multimeter. We can look at DC voltage. We can look at AC voltage. We can examine amperage through a DC voltage connection. We can test for continuity. We can look at resistance, and much more all from this single device.
Any time you’re working with power, you want to be very careful about what you’re doing. You need to understand exactly what you’re connecting to, and what you’re touching with the leads of your multimeter. You also don’t want to connect the leads together with your multimeter. Especially if you’re working with power, because you don’t want to short circuit anything between these two connections. If you have any problems, or any doubts, about what you’re connecting to, the best course is to always call a licensed electrician.
In the United States, our outlets have three prongs on them. One is a neutral, one is the hot, and one is the ground. To check voltages on these outlets, we might connect the voltages between the hot, and the neutral, and see if we are, indeed, getting the standard 120V.
If we’re connecting the neutral to the ground, we shouldn’t be getting any voltage between those two. And if we’re connecting the hot to the ground, we should instead, see 120V coming across our multimeter.
On the inside of our computer case, we can check our power supply output by connecting up the 24 pin connector to our motherboard, turning it on, and seeing what types of voltages we see. We would normally connect one of these probes to a ground connection, and use the other probe to connect to one of the voltages to see if we’re getting the right values from our power supply.
Instead of using a multimeter and individually going through each one of those connections, you might want to use a purpose built device, like this power supply tester. On these, you can plug in your normal power supply and see what type of voltages we’re seeing across all of those different connections. This particular power supply even has an LCD panel that will show us exactly the voltages coming from the power supply. And it’s very easy then, to plug in and immediately see what the status might be.
These are also relatively inexpensive. And they’re so quick to use, that you can save a lot of time just by connecting up one of these power supply testers. On this power supply tester, we would connect the power supply to this 24 pin connection. And then we can connect other components to the other side of the power supply tester. Perhaps the eight or four pin connections, a six pin connection, or a four pin that you might use for something like the case fans.
If you ever wanted to test the physical interfaces that might be on your computing devices, you might want to have available some loopback plugs. These are commonly used for things like serial connections, or RS-232 connections. So you might have a nine pin, or 25 pin serial port loopback plug.
There are also loopback plugs available for network connection. So you have one for ethernet, there might be a different loopback for T1, and a completely different connection for fiber. These are not cross-over cables. They’re simply taking the transmit and redirecting it back into the receive on that individual interface. These are not used to connect up multiple devices. They’re only used to look at a single interface on a single device.
If you’re using a loopback plug, it is almost always fora diagnostics purpose. So you can see if a particular interface is operating how you would expect. You would usually have loopback plugs available for all of the different interfaces that you’re using. There might be one for ethernet, and fiber, and T1 connections. And sometimes you can make your own loopback plug like I did here.
There’s also a nice website you can go to, to make a five-in-one cable that you use as an ethernet cable, a crossover, a modem, a null modem, and a Cisco console all by going to this ossmann.com/5-in-1.html.
Many high end motherboards have an LCD display that tell you exactly what the status is during the boot process. If your computer doesn’t have one of those, you might want to use a post card. The post card for power on self test is one that’s going to give you the same list of LED messages as the system is booting, so that you can see what the status is, and more importantly, where problems might be happening during the boot process.
You can use this external card and connect to a PCI or PCI express bus. There’s also a parallel connection you can connect to as well. And if you’re using the parallel connection, there’s a USB port on many of these post cards that allow you to power up the system while you’re using the parallel port. Whether you’re using an external post card, like this one, or you’re using the built in motherboard functions, this is a great way to troubleshoot and determine what’s happening during the boot process.
Category: CompTIA A+ 220-901