Testing ICs with Multimeter HELP!!

[clanggedin]

I am going to be testing some ICs and a Resistor on a board tonight with a multimeter I just bought last night. I am so new at this testing stuff that I don't know really what I am doing.

How do I test ICs with the meter?? Do I connect the black lead to ground and then touch the red lead to the IC?? Do I do this with power to the board??

Do I need to desolder one end of the resistor to get a proper reading?? I head that to test Capacitors on side needs desoldered is that the case with Capacitors??

Do I always touch black to ground or would I touch the black test lead to negative sometimes

I am trying to help a friend out with one of his boards, but I may be in way over my head.

Any help, like a link to a web page would be appreciated. Searching came up with nothing really useful. This also may be something that could be stickied for newbs like me.

[menace]

To properly test electrical components they should always come out of circuit (i.e. lifting one leg is good enough)  For caps the only way to know for sure is to test them with an esr meter (equivalent series resistance) or use a capacitance function on your multimeter if you have one. 

Most IC's can't be diagnosed with a multimeter without having some knowledge of how the IC is wired internally and most are too complicated for that.  You would need a dedicated tester to properly test it.  Transistors can be checked easily--just do a google search on just that and you should get some hits on simple tests that will indicate your transistors current state.  The same applies to mosfets.  Diodes should only give a reading in one direction and if you are measuring variable resistors or pots, you should have the leads touching the two outside legs and that will indicate the total resistance--to check the range move the red lead to the center leg and turn the put, your resistance should go up or down depending on which outside leg your other lead is on. 

Black is negative/ground but make sure that you are dealing with DC and not AC.  AC can be read in either direction.  hope that helps...

[clanggedin]

Thanks for the help.. I allso found a section about using a DMM on Randy Fromms's site.

http://slot-tech-ftp.serveftp.com:8080/technical_department/general%20electronics/dmm/dmm.htm

[Navmaxlp]

All components should be removed from a circuit prior to testing when checking resistance. The reason for this is, a multimeter actually places a small bit of current through the component under test. Electric current always takes the path of least resistance so if the component is in a circuit and there is an easier path of resistance, you may not be reading what you think you are.

Be careful testing capacitors with a DVM. The afformentioned current can actually charge the capacitor with a voltage and shock you if you touch the leads. (Actually this can be a lot of fun in small doses. Charge capacitor toss to friend, watch reaction).

On an IC chip that is in circuit you can read a few things if power is applied. First off, on all chips, there is a small notch cut out of one end. If you hold the chip vertically with the notch facing up, the top left hand pin is pin one and the top right hand pin is the last. The count goes in a counterclockwise direction so the pin directly below pin one is pin 2 until you reach the bottom then procedes up the right hand side of the chip. If memory serves correct, pin one ios always ground and the last pin is always source voltage. Please remember that IC chips are extremely static sensitive and any electrical charge from your body can destroy it. Best bet is to always ground yourself when testing electronics of any type.

I wrote a guide for transistor testing in the monitor faq. Not worth rewriting the whole thing here.

http://forum.arcadecontrols.com/index.php/topic,14906.msg295222.html#msg295222

Hope that helps and wasn't too confusing.

[Ken Layton]

Testing an IC or a capacitor is best done with specialized ($$) test equipment made just for that.

 I use a Huntron Tracker  ($1,500) for transistors, diodes, and IC's. I also use a CapAnalyzer88a (around$200) for testing electrolytic capacitors as well as a digital capacitance meter (around $100).