Noob Question: How do I test pcb components w/ a Multimeter?

[Silent Shadow]

I'm very new to using a multimeter but I know my way around inside video game systems well enough. I'm trying to figure out how to properly test things like caps, fuses, transistors, resistors, chips, etc that are on pcbs.

I know that if I set my mm to DC V I can gets some responses, but how do I know what I'm actually looking for?

The only thing I have been able to do properly was test AC adapters/power supplies.

I did try searching the forums, but couldn't seem to find what I was looking for.

Any help is really appreciated!

[Kurt_]

caps, fuses, transistors, resistors, chips, etc that are on pcbs.

Continuity: Set your multimeter to the continuity setting (or if it's a cheap digital one, the lowest resistance setting) Nothing means no continuity.

Caps are weird to test. Mostly you just assume that they die or don't die.

Fuses: See continuity, since fuses die by breaking the connection

Transistors: Search Google. I know you use the continuity function.

Resistors: Set your multimeter to the proper resistance range.

Chips: Depends on the chip.


I suggest reading your multimeter's manual.

[Silent Shadow]

Thanks for the input. In between what you have said and leafing through the thin manual on the mm I can now check resistors properly

I realized that part of what is tripping me up is the fact that I'm not familiar with the measurements: how many Ohms = K Ohm, etc etc.

I'm trying to find a good reference chart on this now.....

[Limewater]

Actually, you can't expect to get accurate resistor readings while the resistor is on the PCB.

When a resistor is in a circuit, if you try to measure its resistance, you will actually be measuring the resistance of that resistor in parallel with the rest of the circuit. So, you'll get a resistance value, but you can't expect it to be correct.

But, for the record, there are 1000 ohms in a K-Ohm.

[Kurt_]

Ahh. You're american. That explains some things.

Like most things, (expecially scientific things) the ranges are in metric

K = Kilo = 1000 from the base unit
M = Mega = 1 000 000 from the base unit or 1000 from the kilo unit.
G = Giga = 1 000 000 000 from the base unit, 1000 from the mega unit.

m = Milli = .001 from the base unit.
u = Micro = 0.000001 from the base unit

Or just go here:
http://www.mathleague.com/help/metric/metric.htm

[Silent Shadow]

Limewater - Thanks for the tip. I'll keep that in mind. I was just testing resistors that were not mounted yet.

Kurt - It's not really the prefixes that trip me up, it's more the symbols that represent the units of measurement themselves. It seems that depending on where I look the symbol is represented differently. Sometimes they say "resistance", sometimes it's just "the symbol", sometimes its says "200K" etc etc. So I guess I really just need to read more and get familiar with all the various ways one can write these measurements.

Thanks for the info guys, I appreciate it.

[timmeh87]

you cant really test transistors or caps with a multimeter, at least with only the standard resistace-voltage-current settings.

ive seen multimeters with capacitance measurements, but ditto for what limewater said about measuring components in-situ.

ive also seen multimeters with a simple junction transistor test connector, but the part has to be out of the circuit and it only works on BJTs (junction transistors that is). for the most part the only things you can easily and reliably measure are voltages and resistances, and sometimes current.

for current, you need to put the multimeter in series with the current you are measuring. otherwise you will A) short out your circuit B) get garbage results.