How to use a multimeter to troubleshoot

[Crowquill]

Like many of you, building an emulator cabinet was the first step to buying real arcade cabinets and PCBs. I now have two additional cabinets (a Primal Rage cabinet that I use for JAMMA boards and a Neo-Geo 2-slot). Also, like many of you, I've learned a lot of this stuff as I go and I'm always trying to help out others that are just getting started. One thing that is overlooked by many jumping into this, is the importance of both owning and knowing how to use a multimeter to troubleshoot problems that will arise.

A multimeter is undeniably a tool that you will NEED if you are wanting to own and work on arcade games, pins, or troubleshoot any other electronics projects.

Despite this, there doesn't seem to be any specific info on the site about using one.

I'm thinking it might be good to have a centralized place (updated WIKI entry and maybe a stickied post) to get people started on diagnosing their problems using a multimeter. As with much of this site, I'm thinking that tips on practical applications are best.

Before you jump into working on an arcade game you should already understand basic electronic principles like circuits, voltage (including the difference between AC and DC), and continuity. You will be dealing with a lot of wiring, so you will have to know how to at least crimp on connectors. Eventually you will also have to have a working knowledge of soldering. You will also need to know the difference between wiring things in series versus wiring parts in parallel. If any of these concepts are unfamilliar to you, read up in a basic electronics book before starting.

Anytime you're working with live electricity be very careful. Taking shortcuts, being careless, and jumping in before you know what you're doing can be extremely harmful to both you and your game.

[ChadTower]

Here you go.

[Crowquill]

BUYING

You can pick up one up at a good variety of places. Radio Shack has them, home improvement/hardware stores, Sears, computer stores, auto parts stores, etc.  You can also buy them online many, many places.

I'd stick to a digital multimeter instead of an analog one. Digital will have a nice, large-sized LCD display of numbers. An analog meter will have a peak meter with a moving needle. Digital is MUCH easier to use.

For our purposes, you should have absolutely no problems finding a decent one for $20 or under. For what you'll be using it for you don't need a super-fancy one. On most inexpensive models you'll be adjusting the range that you're measuring manually. This isn't a big deal at all as you'll mostly be measuring voltages over a small range anyway. If you can find a cheap auto-ranging one, it's not a bad feature. Fluke is a brand name that you'll encounter if you do much research on multimeters. Very nice equipment, but for basic testing it's overkill. You also might check out what kind of battery it takes. I've seen RadioShack ones that use a funky 12V battery that would be more expensive to replace than a 9V or a couple AA batteries.

Here are pictures of a common, inexpensive multimeter and a much nicer Fluke one. As you can see the auto-ranging ones have a lot less settings on the dial.

[Crowquill]

HOW TO USE:

Here you go.

I was just about to post that link and give you credit for it.  I thought this might save you some posts. It's probably the best starter tutorial I've seen. My only gripe is that it skips over continuity instead of just giving the really simple explanation that it is.


Here are a few other tutorials:

A Video Tutorial. There's also a downloadable PDF link there that might be good for reference.

If you really have some spare time here's a  29 minute-long video tutorial.

There is a very brief listing in the Wiki that needs to be expanded.

[ChadTower]

To be fair, that's not my web page, I just post the URL when appropriate.

[Crowquill]

How to check voltages in a JAMMA cabinet. This is assuming you've used/tested at least one other board in this cabinet before and know the monitor and speakers are working.

Plug up the JAMMA harness to the PCB, plug it in and hit the switch. Check the voltages that are getting to the game PCB. It has to be tested with a load (connected to the PCB) or you'll get false readings. If you need to learn more about JAMMA read THIS.

I find it's usually easiest to test at the slightly exposed pins on the JAMMA edge connector. Put the red probe on one of the 5V pins and the black on one of the ground pins near it.

If the voltage isn't in the 5.05V-5.10V range, you'll want to look for a knob on the power supply. This'll adjust the voltage to both the 5V lines and the 12V lines. If the voltage is OK, you'll want to hit the coin switches a couple times and hit start. If you still get no sound or video, you PROBABLY have something wrong with the PCB. double-check for a volume knob and check the dipswitches. Some games have a "hold" switch. If this is on, the game will not start.

For troubleshooting and testing it can be helpful to pick up a cheap, known-working JAMMA PCB that you won't be upset if it gets damaged. Personally, I use CombatTribes.

[shardian]

What people who delve into electronics without any prior knowledge should do is go to the book store or local Lowes/Home Depot and get an electronics basics book. Using a multimeter with no knowledge of what you are measuring is the equivalent of a cop using a radar and saying "wow, 97 mph. Wonder what that means? The book says 80 is the max, so it must be bad". (Yes, I know my analogy sucked)

I have the Home Depot- Basic Home Wiring book and it goes over all the tools, including the multimeter, that you will encounter when doing electrical work.

[ChadTower]

Electrical work is different from electronics work, but when it comes to wiring up the power supply to everything, that is electrical.  Electronics work, how to troubleshoot PCB components and trace circuits, that's an entirely different issue that you wouldn't find a book on at Lowe's.  I've actually found it pretty difficult to find good thorough sources on electronic work.

[shardian]

Electrical work is different from electronics work, but when it comes to wiring up the power supply to everything, that is electrical.  Electronics work, how to troubleshoot PCB components and trace circuits, that's an entirely different issue that you wouldn't find a book on at Lowe's.  I've actually found it pretty difficult to find good thorough sources on electronic work.

AC/DC, resistance, continuity, current, etc is the same. That is the basics that needs to be understood before anyone lays a hand on exposed wiring/electronics.
If you are looking at a board with multimeter in hand and wondering whether your setting should be AC or DC, you DEFINITELY need to do some reading.

[ChadTower]

Yep.. I've read a couple of those $10 wiring books from Lowe's... they don't do a very good job of explaining those particular concepts.  They're more about tying wire nuts, making recepticle terminations, mounting ceiling fans and cannister lights.

This book is by far the best all inclusive one I've found on the subject with an eye towards our specific purposes.

[shardian]

Of course, this book would do the best:
http://product.half.ebay.com/Introduction-to-Electric-Circuits_W0QQprZ1697184QQtgZinfo
The first half will read easily enough and teach all of the theory behind what is going on in an electric circuit.

Personally, I have always wanted one of these to learn hands on:
Electronics lab

[ChadTower]

Of course, this book would do the best:
http://product.half.ebay.com/Introduction-to-Electric-Circuits_W0QQprZ1697184QQtgZinfo

Best Price: $0.94
List Price: $125.00 (Save 99%)

 

[shardian]

Of course, this book would do the best:
http://product.half.ebay.com/Introduction-to-Electric-Circuits_W0QQprZ1697184QQtgZinfo

Best Price: $0.94
List Price: $125.00 (Save 99%)

 

It is a college textbook, that original price is very right. I paid close to $100 for my newer copy. It is worth like $10 now.

[ChadTower]

Oh I know, but looking at the two prices together, it's funny.  I used to have calc books that cost $100+ and were "worth" an extra value meal at the end of the semester.

[shardian]

Oh I know, but looking at the two prices together, it's funny.  I used to have calc books that cost $100+ and were "worth" an extra value meal at the end of the semester.

I paid for my honeymoon cruise with half.com and a bunch of books that my bookstore either wouldn't take back, or would only give me pop money for. That was awesome.

[Crowquill]

What people who delve into electronics without any prior knowledge should do is go to the book store or local Lowes/Home Depot and get an electronics basics book. Using a multimeter with no knowledge of what you are measuring is the equivalent of a cop using a radar and saying "wow, 97 mph. Wonder what that means? The book says 80 is the max, so it must be bad". (Yes, I know my analogy sucked)

Good point. A bold note about this and general electricity warning has been added to first post. Did I miss anything?

[CheffoJeffo]

Timely topic -- I was reading the DMM articles in Randy Fromm's Big Blue Book last night and thinking that this stuff is gold. I already knew the basics, but there is so much there.

Worth signing up for his tech department just to get the BBB.

[RayB]

I copied Randy's DMM page, back when it was free...

All you really need to know is the basics.

If measuring AC, set the DMM to AC section.

If measuring DC, set the DMM to the DC section.

Then figure out what the maximum value SHOULD be and set the DMM to the next highest value. So if you're measuring 12v DC, then set the DMM to 20v DC measuring setting.  Touch the ground prong to DC ground. And then touch the power probe to the 12v DC output. Read the value that appears. Easy as that.

[Level42]

http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Atari_TM-129_The_Book.pdf

[torez]

http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Atari_TM-129_The_Book.pdf

Wow nice find, thanks!

Yeah, remember spending around $500 a semester for my books.  At the end of the semester only a few were "returnable" and that's at around 20-25%.  Each year new edition of the books came out, so the company making them would make more money.  All they did is move pages around and renumber graphs/pictures, so if teacher talked about one in class, you would need that new book to understand what's going on.  I'm sure same thing is going on today.  What a ripoff!  I'm surprised nobody sued them for this kind of practice. 

[Level42]

I have to thank Ken Layton for pointing me to the Arcade Archive. Then I did a lot of digging there, very nice site !

I really like that book. IMHO every one here should read it 

Lot's of thing I recognize, because I'm working/educated in electronics. But sometimes you still learn new things, f.i. using a simple pencil eraser for cleaning PCB edge connectors. Before that, I used a glass-fiber pen, but it's much more harsh then the eraser. The eraser trick works great, just did all the connectors on my SW pcb set.

There is one thing I find VERY strange in this book. When soldering, the drawings suggest to keep the soldering iron on the PARTS side of the PCB. I've never been taught this, and I always solder on the solder side.....weird !

[RayB]

There is one thing I find VERY strange in this book. When soldering, the drawings suggest to keep the soldering iron on the PARTS side of the PCB. I've never been taught this, and I always solder on the solder side.....weird !

Shouldn't it be the side with the "traces" ?

[Level42]

Indeed, and that's what I've always seen/learned/heared......check out the pictures on The Book (talk about arrogant !) by Atari

[WunderCade]

Here are a few other tutorials:

A Video Tutorial. There's also a downloadable PDF link there that might be good for reference.

If you really have some spare time here's a  29 minute-long video tutorial.

There is a very brief listing in the Wiki that needs to be expanded.

Chad's link is the best Layman's tutorial for newbs.

The Makezine Tutorial was fine, but the you really couldn't see what they were doing very well.

And the 29 minute tutorial was very convoluted and the presenter had a style that better serves people who already have a rudimentary understanding.

Hands down...Chad's tutorial gets my vote. It's simple and you can print it out into PDF.

[Level42]

Chad found a nice link about how to use an Oscilloscope:

http://www.ionpool.net/arcade/tech/scope_files/scope.html

[RayB]

How about adding an answer to this question:
How do you know when your meter no longer works correctly?

[Level42]

Depends.
Most problems are due to test-leads that go bad over time. I've had that happen once in a while, but I'm using them every working day.

I always test the continuity of the test leads before using the DMM in "diode/continuity mode". That is, I simply short the test-leads and check if I hear the beep. Simple, but essential.

The meter itself. A good one will indicate battery power loss. The really good meters (I've always used Fluke's) seem to run an eternity on their factory set.

If you want to test it for errors then you have to measure a voltage that you KNOW is good. F.I. a power supply that you know is working 100% and you know gives a nice and stable +5V or +12V. If you measure and read something else it's probably the meter.

On AC you could measure mains voltage, but there's quite some tolerance on the mains voltage, remember that.

[purplec]

lads and ladies just a quick question do you check voltages at the board or do check down at the break connectors.

just wondering

thanks purplec

[channelmaniac]

When checking the +5v output of the power supply check it on the board and not at the output of the power supply.

If the wires are too thin there will be some voltage drop. Set the 5v line to 5.0 to 5.1v and you'll be good to go for most games. Some are picky and like the voltage a little higher or a little lower. For example, I looked at a Carnevil game that would get very hot and crash if you gave it more than 4.9 volts. Strange game.

Also, if you suspect your multimeter isn't working then open up the battery compartment and check the fuses. If you hook up DC or AC voltage when measuring Ohms then one or more fuses will blow.

DO NOT PUT OVERSIZE FUSES IN A METER. Yes, I yelled. Ask my 9yr old, I yell whenever there's a safety issue.

[miles2912]

Found a great tutorial on how to measure your pc's power supply voltage.


Link to it

[Mauzy]

Here you go.

Anyone know of an updated link for this? I keep getting a 403 Access Forbidden...

[SirPeale]

Here you go.

Anyone know of an updated link for this? I keep getting a 403 Access Forbidden...

Working for me.

[toomuch45]

thanks for the tips for the multimeter ive used one before on other things but i forgot how it functions but thanks again

[Mauzy]

Here you go.

Anyone know of an updated link for this? I keep getting a 403 Access Forbidden...

Working for me.

Yeah me too. Must have had an off day or something...

[kayoteq]

Here's a good basics of metering tutorial: http://www.ladyada.net/learn/multimeter/index.html


It reinforces my mistake in not doing more research. My 'bad resistors' were fine out-of circuit. After 2 of those, I stopped..

What, in your experience, indicates a true bad resistor in a circuit, other than say, carbon and soot from the short...
or is it truly 'measure, note the odd ones, come back, take it out, measure it, put it back if it's okay, repeat'??

 The ones I r&r'd were, in theory, part of the circuit that I thought was failing.. but they were all fine.

[ChadTower]

Here's a great site on the basics of digital circuits... ties right in with using your DMM to explore them.

[venkman]

thanks for this guide 

[mvsfan]

ive got a good question on multimeters. why do they seem to be one of the only devices that i own that dont have a snap off battery cap? youve either got to take the whole damn thing apart or it has a battery door with 2-4 screws that you have to remove to replace the battery.

this is a simple detail thats highly annoying to me. Its not a big deal but it just seems to me that every single worthless Billy Mays product that my grandma gladly buys always has a snap on battery door.

these morons on the other hand who sell multimeters are in the business of selling electrical testing equipment and they cant get that simple fact right.

[Level42]

Having to unscrew the battery compartment of a quality multimeter is  a safety measure. Depending on the schematics, the battery contact can have connection to a test lead. So there is a risk of electrical shock if you touch it while the multimeter leads are still connected to some dangerous voltage. The screws prevent the compartment from accidentally becoming open in normal operation. And they serve as a hurdle hopefully making you think twice when you intentionally change the battery.

[channelmaniac]

Having to unscrew the battery compartment of a quality multimeter is  a safety measure. Depending on the schematics, the battery contact can have connection to a test lead. So there is a risk of electrical shock if you touch it while the multimeter leads are still connected to some dangerous voltage. The screws prevent the compartment from accidentally becoming open in normal operation. And they serve as a hurdle hopefully making you think twice when you intentionally change the battery.

The screw on back also stays on the meter when it is dropped.

Note, I said "when it is", not "if it is"... all meters will be dropped eventually, and likely way more than once.