Taking the Plunge - Board Repair

MagicMarc-er

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I'm starting to accumulate a number of bad cpu's that are all getting the required amount of power on each pin, but for some reason are not lighting up the led on the board and are not working. Most of these look perfect from a visual standpoint but something on the board is not working right so.....

I need to become proficient at board repair (something I had hoped to avoid) because there just aren't that many people who do this and even fewer who aren't incredibly backed up with work. Is there anywhere in this forum or on youtube or wherever, that gives a good primer on troubleshooting and then repairing boards? I have some rudimentary experience with a soldering gun but I'm not even sure how to test the individual components on a cpu to figure out where to begin.

Any advice would be greatly appreciated.
 
You are going to want a logic probe and become familiar with data sheets and schematics.
 
Pick one title and obtain a working version and several non-working boards. That way you have a "test standard" to compare the non-working boards against.

One word: Oscilloscope. You can "see" what's going on with the signals on the board.


Bill
 
You can see the signals with a scope, but it doesn't do any good unless you know what yer lookin' at. I don't recommend a logic probe....they will trigger on bad signals and make you chase your tail endlessly. Fine for checking for stuck switch inputs tho.

Board repair is *not* something you can learn in a couple hours. It can get quite involved and lots of digital theory comes into play on the tough ones (comparing timing signals, etc).

I'd recommend getting a good handle on basic electronics first, then start to study digital and CPU theory. The control pins on a CPU can tell you alot about what is going on when the board won't run. There are conditions that need to be met before the CPU gives the green light and it doesn't take much to throw a wrench in the works.

So by all means if you are interested in learning to repair older digital boards, go for it. Just be warned that you *will* invest a good amount of time before "getting a clue", and it can take years to get good at it. If the only reason for wanting to learn repair is just to get one board working, its prolly not worth the effort.
 
Thanks for the great responses. Maybe I should revise my question to include only the easiest or most common board problems.

For example, assuming a board is getting the right voltage on all inputs, and all traces have continuity, what would be the next logical step (regardless of which game the board came from)? Check resistors, or capacitors, or voltage regulators, or diodes or something else?

It would be great if there was some type of board repair checklist so you don't waste time on the least likeliest (or most difficult to repair) problems first.
 
Verify sockets first. They were cheap to begin with because the boards weren't expected to last 30 years. Then verify the contents of the roms. One bad one will keep the game from coming up. Look at data/address lines to verify they are running and are of valid logic level and "clean". Make sure none are shorted to each other. Look at the output lines of all rams to verify none are stuck. This can get tricky as you can have a bit stuck internally but the output(s) will still look fine. Check control signals at the CPU and make sure they are what it wants to see to allow the code to run. Etc, etc.

Vector games have their own set(s) of "rules" you need to have a handle on to t-shoot.
 
If you have a pcb not booting I would asusme once voltages are verifuied etc that check clock signal and reset lines comes next?
Then you can verify if the cpu itself, z80 or 6502 or whtever it happens to be itself is running at the IC level. Then maybe you can find out if it is not running, what other components are needed for the ic to run, and check those or if the cpu is running at ic level you can then see what things connected to it are not running. Honestly I know about enough about this to get myself in and out of trouble, if I missed some steps in a trouble shoot bubble map style some one else please add them.
 
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Sorry to dissapoint but you can't become a board repair technician overnight. To be good at it you need to first know how to solder and de-solder without giving it any thought or you are going to hack PCBs to bits.

Then you need to UNDERSTAND what each and every component does and what it is there for - - - most times without any schematic diagrams.

Like others have said - first do a basic electronics course because unless you have a sound background in what each part is for you will never move forward and be able to diagnose things.

There is no such thing as a 'step-by-step" how to fix guide because EVERY piece of electronics is different in some way even though they are often built from the same basic building blocks. You need to learn about and understand each of those building blocks so that you can then apply that knowledge to the repair in front of you.

There are no shortcuts to learning this …......
 
Personally marc, I don't think its all doom and gloom like I feel other responses make it sound...
 
I think you have a chance of success. There is a sticky at the top of this forum, start there. I agree that you won't become a successful board tech overnight, but you don't need professional training to do it either. I've had an interest in electronics since high-school and have spent the last 25 years doing it as a hobby. I've never been "professionally trained", attended any electronics schooling, etc.; but I have successfully repaired my own boards and boards for others.

You've got to start somewhere, I would just reccomned that your first board repair isn't one that you value highly. Expect to fail your first try and you can't be dissapointed.

Good Luck. I still remember the exhilleration of my first successfull board repair...

Brian.
 
Ignore the naysayers - I don't think they were trying to discourage you but the common theme is that in any pursuit, some sweat will be needed.

The best advice I saw was to suggest reading the stickies here and other arcade repair resources.

You'll find that repair techniques become like a personality - everyone has their favorite way to go about it. Like I posted earlier, if you pick one game board and become proficient at repairing it, you will gain the knowledge and confidence to branch out.

And most importantly - have fun - if you you are not having fun than do something else with your spare time that is fun.

Bill
 
I agree with most of the above posts but the soldering issue. I have seen very good techs that could not solder AT ALL and never owned an iron. How can this be you ask, he had a out of work person that he hired for baby sitting and this person was a re work tech also. He would test the board and have her change the parts. Worked great for him.

You need to read though this

http://forums.arcade-museum.com/showthread.php?t=177192

Then I suggest download the Atari book, it is in that thread I think.

Then look at this thread...

http://forums.arcade-museum.com/showthread.php?t=228509&highlight=ttl+book

And download one of these...I use the pocket one all of the time..

http://www.onecircuit.com/node/27

Lots of reading I know. If you get a chance go to a repair party and yes they do come up once in a while.

Soldering is best done on an old television or something like that until you get better. A good soldering iron will help.

MOST OF ALL, ask questions if you are unsure about something. It takes a few mins. to read and reply to a post. It can take hours 2 days to find a problem that may have been a simple fix, dips comes to mind here.

The best way, in my opinion is with the scope and a working board set. Lately it has not been working for me. I have several Operation Wolf boards that I am working on, with little luck.

Good luck and enjoy.

p.s. When you get you first board fixed, That is a great high.
 
Personally, I've been following threads that are detailed & with good responses. Even though I don't have a G08 right now, I'm paying attention to that thread, studying the pics, thinking about the problem & solutions. Those examples are very good ways to add to your knowledge.
 
I'd recommend putting your location in your profile. It shows everyone where you are from and you might find yourself getting invited to a local repair party.

I just posted a new thread about hosting another repair party here in the Dallas area.

RJ
 
Those links are phenomnial! You have rep sir!
I agree with most of the above posts but the soldering issue. I have seen very good techs that could not solder AT ALL and never owned an iron. How can this be you ask, he had a out of work person that he hired for baby sitting and this person was a re work tech also. He would test the board and have her change the parts. Worked great for him.

You need to read though this

http://forums.arcade-museum.com/showthread.php?t=177192

Then I suggest download the Atari book, it is in that thread I think.

Then look at this thread...

http://forums.arcade-museum.com/showthread.php?t=228509&highlight=ttl+book

And download one of these...I use the pocket one all of the time..

http://www.onecircuit.com/node/27

Lots of reading I know. If you get a chance go to a repair party and yes they do come up once in a while.

Soldering is best done on an old television or something like that until you get better. A good soldering iron will help.

MOST OF ALL, ask questions if you are unsure about something. It takes a few mins. to read and reply to a post. It can take hours 2 days to find a problem that may have been a simple fix, dips comes to mind here.

The best way, in my opinion is with the scope and a working board set. Lately it has not been working for me. I have several Operation Wolf boards that I am working on, with little luck.

Good luck and enjoy.

p.s. When you get you first board fixed, That is a great high.
 
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