I will update this some more when I get learn some more case specific use for it with the xbox. Below I have added a little more of what I know.
A multimeter is a black box of electronic circuitry that allows you to troubleshoot just about any type of electrical wiring or device. You simply dial the proper function and scale, touch the two test leads to the wiring or device in question and check the meter reading. Depending on the setting, the multimeter will tell if you have a broken connection, no power, poor connections, faulty parts and more.
With all its numbers, dials and switches, a multimeter (also known as a volt-ohm meter, or VOM) can be pretty intimidating. Yet its well worth learning, is relatively inexpensive and should be in the toolbox of anyone seeking to do wiring diagnostics and appliance repair. Here, well walk you through the basics and show you six quick, down-to-earth tests you can safely use today.
Your VOM can pay for itself quickly by simply analyzing whether the dozens of batteries devoured by toys and electronic devices are still good (Photo 1). But only using these instruments to check batteries is like harnessing a draft horse to pull a roller skate. Explore a sampling of other possible uses, as shown in Photos 2 6.
Multimeter terms
(IMG:
http://www.keepmedia.com/Pubs/display/2004/08/26/455074.jpg)
Its hard to visualize electricity, so Ive always thought of it like a river. In a river, theres a certain volume of water (similar to electrical amperage, or amps) flowing with a certain potential force (like voltage) that encounters obstructions as it flows (resistance measured in ohms). Hold that big picture in your mind, then add these key concepts about both electricity and VOMs:
Alternating current (AC) voltage: The type of electricity that powers your house.
Direct current (DC) voltage: The type found in auto and household batteries.
Resistance (measured in ohms): The lower the reading, the easier electrical current (measured in amps) flows through circuit material.
An open circuit equals trouble: There is high resistance from a broken connection, a faulty part or a switch thats been turned off. There isnt a complete circuit path and no current will flow.
A closed circuit is good: It means a minimum of resistance is present because a connection or part is working. Note: Check the pathways in the wiring or device being tested for any random loose wiring thats touching the circuit youre testing. Sometimes a broken connection (short circuit) can look like a closed circuit. Short circuits can harm you, destroy equipment and start fires.
Continuity testing determines if an open, shorted or closed circuit exists in an appliance, electrical or electronic device and is a common use for multimeters.
On a VOM, infinity signifies an open circuit. On an analog multimeter, infinity shows up as an unwavering needle that wont move off the far left side on the display. On a digital multimeter, infinity reads 0.L.
On a VOM, zero means a closed circuit has been detected. The display needle moves to the far right side of an analog scale; zero reads 0.00 on a digital VOM.
Selecting the proper range is very important and refers to setting the function switch on your multimeter to a voltage or amperage value thats higher than the top value you anticipate testing. Digital multimeters have a nifty feature, auto-ranging, that automatically selects the widest possible range once you set the function switch for ohms, current and voltage (AC or DC). Auto-ranging gives you the safest testing capacity each time you change back and forth from, say, measuring resistance to voltage readings.
USING VOMs
Both types of multimeters require you to decide which to test for first: ohms, voltage or current. Next, select the range youll be testing. For example: On an analog multimeter, if you were to test AC voltage in a 120-volt wall outlet, but only set the function switch to 30 AC volts, youd overload and damage the multimeter. Instead, select a setting greater than 120 AC volts.
VOMs come with two colored testing probes that connect to jacks in the meter. The probes have electrically insulated handles with metal tips. Generally, the red probe plugs into the + meter jack and the black probe plugs into the - jack. When the test probes contact a circuit, the findings are displayed on the LCD readout or analog meter scale.
A test for voltage and amps uses the electricity present in a live circuit to power the meter. For resistance (ohms) and continuity tests, batteries inside the VOM send a weak current through the circuit being tested to get the reading. We suggest you stay away from live circuit tests until youve mastered using the VOM on the resistance and continuity tests we show. Before running a resistance test, avoid possible injury to yourself and damage to the multimeter by disconnecting power to appliances and shutting off circuits.
GOOD TECHNIQUES
When testing DC voltage or amps, match the polarity of the probes to the + and - terminals of the DC source being measured. Matching polarity isnt necessary for testing either AC voltage or amps, or for continuity or resistance readings.
For the most accurate readings, hold the probe tip points (not the sides) tightly to a contact. Avoid touching the metal tips with your fingers. Your body could act as a circuit and influence a reading (and get you zapped!).
Each time you do an ohms test using an analog multimeter, touch the two probes together and use the calibration dial to zero it out. For a digital multimeter, touch the probes together and it automatically calibrates itself.
Ensure accurate readings by periodically cleaning oxides off the metal probes and keeping the tip points sharp with fine-grit sandpaper or emery cloth.
DIGITAL VS. ANALOG VOMs
For appliance and electronic repairs, buy a digital, not analog, multimeter. This type is much simpler to read and you can change the functions on it more easily. Digital multimeters (Photo 2) have LCD readouts, do continuity testing, and cost from $35 on up. Some digital multimeters also feature auto-ranging and overload protection and other advantages analog multimeters lack.
Analog multimeters have multiple scales on the dial (Photo 1), a moving needle and many manual settings on the function switch. Its tricky spotting the correct scale to read on the dial, plus you sometimes have to multiply the reading by 10 or 100 to get your final value. Depending on features (make sure it can do continuity testing), prices start at about $15.
For easier, hands-free viewing, choose a multimeter with a stand that will prop it up or hang it on a wall. If a multimeter doesnt come equipped with either jumper wires or alligator clips (both about $4 each), buy them. Alligator clips are often used to firmly grip wiring or contacts for hands-free safe and accurate readings. Both types of multimeters and these accessories can be purchased at electronics stores, home centers and hardware stores.
TESTING AN XBOX FUSE
On all versions, 1.0-1.6 there is a small fuse located right behind where the power cord plugs into the PSU.
One versions it looks like a small black round cylinder with T3.15a 250v printed on the top.
On another version it looks like a small white tube with silver endcaps on either side, and has T3.15a 250v engraved on the silver. It also has T3.15a 250v printed on the circuit board just below it.
On the last version it looks like a little black piece of rubber tube sticking up with CSA LR116075 printed in white on the side.
On all the versions you can follow where the wires from the fuse run into the board, and then flip it over to see where they are soldered into.
To test the fuse you need to set it to 15 or 20 volts DC. The symbol on the multimeter for Volts DC has a V with a long line, and a dotted line underneath of it.
make sure the powercord is plugged in, and the system is turned off, and touch the red probe to one end of the fuse, and the black probe to the other. You should get a reading of 0.03 or 0.02 on the multimeter. If you don't then the fuse needs to be replaced. On an analog multimeter (the one thats not digital) The arrow should not move if the fuse is good.
If the fuse is good and you are still not getting any power, than the next step is to see if there is any power going to the motherboard. Leave the multimeter on the same setting and with the xbox plugged in and the power off, take the at or atx connector (the thing that plugs into the motherboard from the PSU) and touch the black probe to one of the black wires the run into the at/atx connector, and touch the red probe to the 3.3v standby which is the violet, or brown wire. You should get a reading between 3.15 and 1.45. If you don't than the PSU is dead and needs to be replaced. If you do, than you press the power on the xbox and test the other wires in the same way, always touching the black probe to the black wire.
Yellow: 11.5-12.5v
Red: 4.85-5.25v
Orange: 3.15-3.45
If all the wires test out ok, than the PSU is fine, and there is a problwm with your motherboard.
Below is a list of what the colored wires are, and what there voltage is. They names are color coded and go in the order they do on the PSU.
Delta 12 pin PSU
+12v
+5v
+5v
+5v
+3.3v
+3.3v standby
ground
ground
ground
ground
power on
power ok
Foxlink 12 pin PSU
+12v
+5v
+5v
+5v
+3.3v
+3.3v standby
ground
ground
ground
ground
power on
power ok
Mineaba 12 pin PSU
+12v
+5v
+5v
+5v
+3.3v
+3.3v standby
ground
ground
ground
ground
power on
power ok
Delta 20 pin PSU
power on power ok
ground ground
not used +3.3v
+3.3v not used
not used ground
ground +3.3v standby
not used ground
+5v +5v
+5v not used
+5v +12v
When I learn more, I will update this tutorial. Until then, I hope this will hope everyone.
This post has been edited by villevalo: Nov 16 2004, 09:01 AM
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Topic: Multimeter Tutorial (Read 71 times)