Examining PCBs Last Updated on: 6/19/2013

I make no claims as to the accuracy of the information provided here. It is "AS IS" and you are warned to use this information "At your own Risk"

This information is provided to help you restore or convert your video games. The Tips & Tricks are what have worked for other people to some degree. Your mileage will vary depending on your situation.

I really do appreciate the fact that these individuals have spent the time and effort to share their knowledge with us.

If you have a Tip or Trick that you would like to add to my site, please drop me an email.

I reserve the right to edit for content, and formatting.

 

Another tip from Mark Jenison!

Editors Note: Please be sure to see Bob Roberts note at the end as its an important side note to this tip. If you are not familiar with the terms "Solder Side" and "Component Side", its very easy. The side of the board that has all the chips, resistors, etc.. on it is the "Component Side" and the side where everything is soldered, is the "Solder Side"

Here is his Tip:

Simon Whittam e-mailed me about writing something up about this topic and gave me a few ideas about it's content, so I've got to give credit where is due. Most of this is common sense stuff, but it's written more like a procedure document for beginners. Follow up the thread with tips of your own.

I've been learning a lot from the follow ups that people are posting. Great information, guys! I'm glad to see people are enjoying these little articles.

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Small Tip #9

Frequently, you'll run across arcade boardsets which are in untested condition; you see them being sold on the newsgroup or pick them up from your local amusement operator. These can be trash or treasure once you test them, but there's a few things you'll want to do before you get that far.

Visual inspection of the board is very important. There can be a lot of tell tales signs that can save you a lot of debugging time down the road if you look carefully.

Depending on the condition of the board, you may want to clean it first. If it's been sitting on a shelf for years, it probably needs a good cleaning. If it's relatively clean, skip this part.

Let's start on the solder side first.

Check the bottom of the board for previous work. Are there surface wires or signs of resoldered devices? Check the work, and try and speculate why it was done.

Next, check for scratches, cuts and scrapes on the bottom. When boards get stacked or boxed together, devices and heat sinks can scratch the bottom of boards and cut traces. If you see any deep scratches, use a multi-meter to check continuity along the traces to make sure none were cut. I bought a few boxes of boards from Great Western Trading company a few years back, and 50% were fixed by simply repairing cut traces on the solder side. Sometimes a scratch will smear two traces together, so you should check them for shorts, too.

Also, sometimes the IC legs stick so far out the bottom that they can be folded over onto other traces. Make sure the IC legs are not folded over and shorting to another trace it's not supposed to. Check for solder blobs or splashes that may be inadvertently shorting two lines together, especially if there is evidence of previous amateur work.

Resolder any and all header pins; these are the pins which stick out perpendicular to the boardset where the connectors attach to. Williams boards, along with Tempest and Battlezone boards, are notorious for having cracked solder joints at the header pins.

Now, flip the board over to the parts side.

Check socketed devices for corrosion; I've seen IC legs that look fine in the socket, but crumble to dust when removed. I've been told to use an eraser tip to clean the IC legs, but for years I've used a small piece of sand paper and just sanded LIGHTLY and haven't had any problems. If the socketed devices look clean, it doesn't hurt to reseat them; pry them up with a small screw driver and push them back in. Check to make sure that the IC legs do not fold when you re-insert them. Verify that all devices are correctly oriented (all their "notches" face the right way).

Also, check for missing devices. Sometimes operators will pull valuable chips from boardsets. However, not all sockets on all boards are supposed to be populated (there's no EPROM #5 on a Defender ROM board, for example). Always question empty sockets.

Next, check for broken devices. Anything that has a higher elevation than the other parts is likely to have been crushed if stacked upon. Trim pots and clock crystals are frequently broken devices (if your board has no clock crystal on it, you know something is wrong :-)). Large capacitors also should be checked. Wiggle them a little bit; they should be firm. If one (or more) capacitor legs are loose and sliding in and out of the cylinder, you should probably replace it. You'll have to look closely to find problems with the smaller devices like broken diodes and broken or burnt resistors. Check for burnt or cracked ICs and transistors, too. If you have to replace an IC, remove the IC and put a socket in it's place first.

Clean off the edge connector (if there is one) using the same method above for cleaning IC legs.

It's ready to be tested!

Needed
------
Tools for soldering
Multi-meter

References
----------
To take your board testing one step further, see
http://www.spies.com/arcade/info/Identify-unknown-boards

Advanced Tips

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Find a ground and +5VDC rail and ohm them together. They should not be a direct short (0 ohms). If they are, something is very wrong, but finding out exactly what is wrong is the hard part. Do this with the other power rails on the board. I usually hook up my volt-meter to ground and +5VDC points on the board so when I switch on the power, I can monitor the power coming up (and switch it back off quickly if I'm not getting what I expect).

--

As always Bob Roberts has good advice, and this subject is no different :-)

Mark...my invited comment would be as I have said before, even though you have not experienced any problems, I would never bring sandpaper to the game. Remember that sand is not a conductive, but rather a dielectric in it's natural state, before being sent out to Silicon Valley, and can therefore present some troubles caused by the falling particles of sand.

I agree that an experienced tech could get away with this even though it is very abrasive and can take the nickel plating off the legs of ICs & edge pads, but if it is practiced, I think that Scotch-Brite is much safer & easier to use even though it has the same draw back as an eraser or sandpaper....the dielectric debris can get into a crevice that could & does open a circuit, especially when reseating chips.

In a shop, where an air compressor is routine equipment, it is not as much of a problem, but it can happen under those circumstances, as well.

Keep up the informative posts....great stuff! We'll have a new generation of collector/techs, which there is a shortage of at present.

Happy Gaming.....
--
Big Bear Thanks The Real Bob Roberts
For parts http://personal.msy.bellsouth.net/~bob147

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