How to fix PCBs - A Beginners Guide

ok..I read most, not all of this thread (and others and watched youtube vids)

...and I have a stargate with no sound but WAS playing...then one day i turned it on and got the 1-3-1 error (which from reading online is a common error)...BEFORE i got the 1-3-1 error on the stargate i did replace the sound bard with a working one and i did get sound....so for stargate sound problem it is definitely just the board itself and nothing else...as far as the 1-3-1 ive done all troubleshooting i can think of (with my limited knowledge) and i still get it 1-3-1.

I also have a sinistar that plays but no sound...and again...put in working sound board and got sound.

For the stargate i have replaced the 1-3-1 error chip with others on the board and I still get the 1-3-1 error...you know..the swapping of positions routine.

I have had someone walk me thru (over the phone) testing the voltages on the stargate and all spots tested were within range to be considered receiving enough voltage in all test areas.

But I need to ask....can someone do a detailed step-by-step video of EXACTLY how to use a logic probe to trouble shoot a board/chip?..I read what you guys/gals post...and i appreciate it greatly..i really do.....and I know it is a lot to ask, but a vid would help me and others out so much...and ive done all the youtube/internet searches on the subject....but still in the dark on it...Every vid i've watched is vague...."this leg is reading high......this leg is reading low...etc..etc".....then the vid cuts away and resumes "ok...i fixed the chip that was reading wrong....it works now....bye..thanks for watching."....makes me want to pull my hair out....HOW WAS IT READING WRONG??!!,,,,WHY WAS IT READING WRONG??!! hahahaha....drives me crazy.

I'm always left asking to myself: what is high??.....what is low???....what exactly is what??? how do know what each leg is supposed to read????....if a leg is reading wrong, how do you remedy it??...how do you tell a leg is reading wrong??....the logic probe beeps..lights up.....where do you find out which leg is supposed to beep at what level??...green lights up on probe??..red lights up on probe?? What what what?!?!....It's just nothing is exactly clear to me....I read up on things but i need to physically see it being done start to finish: Here is the chip to test...here is where i find out what the legs are supposed to read....hi means this...low means that...if its supposed to be "low"..and it doesn't read as such, then we have to do this......etc...etc.

I dunno..i guess im venting my own frustrations within myself for not grasping everything as quickly as i think i should....i have two games i cant play and its driving me bonkers....ive multimetered the life out of both of them.....resolders the headers....i bought the logic probe as "the next step"...but i really am lost on it.
 
ok..I read most, not all of this thread (and others and watched youtube vids)

...and I have a stargate with no sound but WAS playing...then one day i turned it on and got the 1-3-1 error (which from reading online is a common error)...BEFORE i got the 1-3-1 error on the stargate i did replace the sound bard with a working one and i did get sound....so for stargate sound problem it is definitely just the board itself and nothing else...as far as the 1-3-1 ive done all troubleshooting i can think of (with my limited knowledge) and i still get it 1-3-1.

I also have a sinistar that plays but no sound...and again...put in working sound board and got sound.

For the stargate i have replaced the 1-3-1 error chip with others on the board and I still get the 1-3-1 error...you know..the swapping of positions routine.

I have had someone walk me thru (over the phone) testing the voltages on the stargate and all spots tested were within range to be considered receiving enough voltage in all test areas.

But I need to ask....can someone do a detailed step-by-step video of EXACTLY how to use a logic probe to trouble shoot a board/chip?..I read what you guys/gals post...and i appreciate it greatly..i really do.....and I know it is a lot to ask, but a vid would help me and others out so much...and ive done all the youtube/internet searches on the subject....but still in the dark on it...Every vid i've watched is vague...."this leg is reading high......this leg is reading low...etc..etc".....then the vid cuts away and resumes "ok...i fixed the chip that was reading wrong....it works now....bye..thanks for watching."....makes me want to pull my hair out....HOW WAS IT READING WRONG??!!,,,,WHY WAS IT READING WRONG??!! hahahaha....drives me crazy.

I'm always left asking to myself: what is high??.....what is low???....what exactly is what??? how do know what each leg is supposed to read????....if a leg is reading wrong, how do you remedy it??...how do you tell a leg is reading wrong??....the logic probe beeps..lights up.....where do you find out which leg is supposed to beep at what level??...green lights up on probe??..red lights up on probe?? What what what?!?!....It's just nothing is exactly clear to me....I read up on things but i need to physically see it being done start to finish: Here is the chip to test...here is where i find out what the legs are supposed to read....hi means this...low means that...if its supposed to be "low"..and it doesn't read as such, then we have to do this......etc...etc.

I dunno..i guess im venting my own frustrations within myself for not grasping everything as quickly as i think i should....i have two games i cant play and its driving me bonkers....ive multimetered the life out of both of them.....resolders the headers....i bought the logic probe as "the next step"...but i really am lost on it.


Smart Bomb, I can appreciate your frustration, not being a trained engineer myself. I have seen those videos where they never show how they came to the conclusion said chip was bad. While it's kinda hard to do a step-by-step since every game and chip is different; I can offer my understanding of logic chips and their behavior. Your frustration comes from what I understand is a lack of knowledge of how these components operate. You really do need to understand that before you can then understand if a chip under test is faulty.
logic probes are cheap too, so they are very accessible, but that does not diminish the need to know how to use it, which is much less accessible.
Bob says it perfectly:
"This is far & away, the cheapest & easiest way for a collector to T-shoot a board, once the basic skills are captured." The Real Bob Roberts™

But here goes:

Logic chips operate by energizing one or many pins on a chip with typically 5 volts. When 5 volts is present on a chip leg (either coming in or coming out) that is interpreted as a logic High. anything other than that, like no volts, or less that 5, that is a logic low. Chip legs have different purposes and all chips are different. Some legs are just to power the chip, that pin should always be high. another pin will be the corresponding ground pin, that will always be a logic low. other pins will pulse on and off, that will show it going high on and off.

How do you know what should be what?
By interpreting 2 things:
1) the datasheet for that chip. This sheet will show the leg assignments and what their stock behavior is
2) combining above with interpreting the schematic for that game. The chip may be manufactured to behave a certain way, but its use in the circuit may change that. so you need both to understand what is "should" be doing.

From there, then, you test each pin and observe what it's doing while in operation. The probe itself is laid out kinda easy, there are led's to indicate high, low, as well as indicating if the pin is going FROM high to low, or going FROM low to high. That is equally important as the circuit may be switching off a signal, or turning one on.

What do you do if a leg is not doing what it should?
Generally it means you should remove it, and swap it with a known good one; and see if that solves your problem.

the thing is, the circuits can get complicated FAST. You may find a chip that's bad (you think, from observed testing) you also need to know that maybe that observed issue is cause by a component before.... or AFTER that chip.
I find it helps to troubleshoot the board from a holistic view, but troubleshoot the circuit in a compartmentalized fashion. Most boards are designed where components near each other tend to be related.

I do hope that helps, and continue investigating and learning. Don't stop asking questions, and keep in mind your issue may be beyond your capability.


This is a decent link:
http://wiki.arcadeotaku.com/w/Logic_Probe_Guide

and here is a straight up manual, that shows the possible states indicated:
http://burningsmell.org/media/micronta-logic-probe-22-303.pdf
 
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Smart Bomb, I can appreciate your frustration, not being a trained engineer myself. I have seen those videos where they never show how they came to the conclusion said chip was bad. While it's kinda hard to do a step-by-step since every game and chip is different; I can offer my understanding of logic chips and their behavior. Your frustration comes from what I understand is a lack of knowledge of how these components operate. You really do need to understand that before you can then understand if a chip under test is faulty.
logic probes are cheap too, so they are very accessible, but that does not diminish the need to know how to use it, which is much less accessible.
Bob says it perfectly:
"This is far & away, the cheapest & easiest way for a collector to T-shoot a board, once the basic skills are captured." The Real Bob Roberts™

But here goes:

Logic chips operate by energizing one or many pins on a chip with typically 5 volts. When 5 volts is present on a chip leg (either coming in or coming out) that is interpreted as a logic High. anything other than that, like no volts, or less that 5, that is a logic low. Chip legs have different purposes and all chips are different. Some legs are just to power the chip, that pin should always be high. another pin will be the corresponding ground pin, that will always be a logic low. other pins will pulse on and off, that will show it going high on and off.

How do you know what should be what?
By interpreting 2 things:
1) the datasheet for that chip. This sheet will show the leg assignments and what their stock behavior is
2) combining above with interpreting the schematic for that game. The chip may be manufactured to behave a certain way, but its use in the circuit may change that. so you need both to understand what is "should" be doing.

From there, then, you test each pin and observe what it's doing while in operation. The probe itself is laid out kinda easy, there are led's to indicate high, low, as well as indicating if the pin is going FROM high to low, or going FROM low to high. That is equally important as the circuit may be switching off a signal, or turning one on.

What do you do if a leg is not doing what it should?
Generally it means you should remove it, and swap it with a known good one; and see if that solves your problem.

the thing is, the circuits can get complicated FAST. You may find a chip that's bad (you think, from observed testing) you also need to know that maybe that observed issue is cause by a component before.... or AFTER that chip.
I find it helps to troubleshoot the board from a holistic view, but troubleshoot the circuit in a compartmentalized fashion. Most boards are designed where components near each other tend to be related.

I do hope that helps, and continue investigating and learning. Don't stop asking questions, and keep in mind your issue may be beyond your capability.


This is a decent link:
http://wiki.arcadeotaku.com/w/Logic_Probe_Guide

and here is a straight up manual, that shows the possible states indicated:
http://burningsmell.org/media/micronta-logic-probe-22-303.pdf

That is the 1st step i was looking for.....i had a small grasp of what the deal was from reading everything and watching vids....but was still clouded ....and your write up lifted the fog a little more for me. I greatly appreciate it. This was the kind of explanation I was looking for to get me thinking correctly. It did not clear it ALL up for me but helped me understand a little more than I did yesterday.
 
Logic chips operate by energizing one or many pins on a chip with typically 5 volts. When 5 volts is present on a chip leg (either coming in or coming out) that is interpreted as a logic High. anything other than that, like no volts, or less that 5, that is a logic low.

Actually, it's a little different then that.

Typically if the voltage is between 0 and .8V it's considered LOW, if it's between 2 and 5V then it's HIGH. (http://en.wikipedia.org/wiki/Logic_level)

Some IC's can be different from that, but it should be pretty standard.
 
Actually, it's a little different then that.

Typically if the voltage is between 0 and .8V it's considered LOW, if it's between 2 and 5V then it's HIGH. (http://en.wikipedia.org/wiki/Logic_level)

Some IC's can be different from that, but it should be pretty standard.

Agreed, but I wanted to make this as simple as possible to understand.
 
That is the 1st step i was looking for.....i had a small grasp of what the deal was from reading everything and watching vids....but was still clouded ....and your write up lifted the fog a little more for me. I greatly appreciate it. This was the kind of explanation I was looking for to get me thinking correctly. It did not clear it ALL up for me but helped me understand a little more than I did yesterday.



Very happy I could help!
 
If you're looking at repairing surface mount items it can be very difficult to determine which parts are bad. Use your eyes and look for things that are cracked, burned, or missing. Empty spots on the board will have smooth solder sitting on the pads but parts that are missing will leave telltale marks that will help you immediately see that something used to be there.

For chip resistors, look closely at the part. If you see a pinhole in the middle of it - right smack dab in the middle of the writing on it - then it's bad. You may need a small magnifying glass or loupe to see it.

If a part is smoked you may be up a creek on the replacement of it. Sometimes you can see patterns in parts around it and make a determination as to what it should be. Other times you can guess based on the function in the circuit such as a missing cap that is connected between power and ground. That will be a .01 or a .1uf cap in most cases.

Ordering can be daunting but check page 9 of this PDF for what size codes for ordering equates to in real world measurements.

http://www.token.com.tw/pdf/chip-resistor.pdf
 
Ah bummer, I didn't see the manual anywhere. I saw these on Ali Express but I'm always weary of Chinese products like these, glad I asked.
 
As for Vectors alot of the same things apply. The major difference is in the DVG, or AVG sections. Digital Vector Generator, or Analog Vector Generator.

As already stated Power is the first thing. Get your schematics out, and start checking the power supply. Check both the DC power, and AC. Also check for AC ripple on your DC circuits. If you have to much AC ripple this will cause problems. That is why you see posts about people replacing the Big Blue and it fixing their problems. Big Blue filters out the AC ripple.

Connectors, These are the downfall of any electronics. They are a necessary evil, and will cause more problems than just about anything else. Corrosion, poor contact, cold/cracked solder joints on headers from removing and installing connectors over and over.

Aux boards on Atari Vector games have these nice wide connectors on them. If the game hasn't been repaired before, you can bet you have cold/cracked solder joints on these. Re-flow, Replace, re-build these guys everytime!

Sockets, I don't think anyone has touched this subject yet. Alot of games used single swipe sockets, meaning the socket only touches one side of the chip leg. These are often the ones you hear about people replacing. A dual swipe socket which costs less than .20 cents can go along way in getting a game up and running. Alot of times you will find that legs on the sockets are cracked, and will only make intermittent connection, or the contacts are corroded and don't make good contact, or introduce to much resistance.

BattleZone boards seem to be the worst as far as Vectors go. Which is why you see the multi game ad ons take care of a dead board. They use the CPU socket which tends to be a better socket, and it eliminates up to 8 possibly bad Rom sockets.

Sometimes just doing these few basic things will get you up and running. If not, you've got your work cut out for you.

Next is the clock circuit, without this, nothing will work.

Then for Chips, I like to check them in this order.
CPU
Roms
Rams

Womble, and Channelmanic have already covered this pretty good, so no need to cover them again.

Unless you have an IC tester, and a Programmer it's going to be difficult to test Roms, CPU's and Ram.

Next comes the fun part, are the Rom, Rams, and CPU talking?

Easy way to tell is with a Fluke 9010a, Signature analysis, and or the Logic Probe. Some games will thankfully have Self tests to help out, pointing out bad Ram, and even tell you which one. The self test code takes up a small portion of rom space, and if you have a Good CPU and Clock it will most generally run. You're only problem is if you don't have video out. The ram test will typically beep, but Rom failures are generally displayed.

A nice thing about games like Tempest, Battlezone, or any Atari Vector that uses an Aux board. It will run self test without the aux board. This way you can check video out, Ram, Rom test etc.

Hopefully at this point you have the MPU side of things working, and if there is nothing wrong with the Vector Generator, you should at least be able to play blind.

The video out on vectors typically requires an oscope. Just makes things easier when you can see the signal.

Tempest for Example will have 6.8vdc, +-15 Vdc and a Digital +5v there are test points on the board for those. Missing any one of these voltages and you won't get any video. So test those first.

The X and Y outputs swing from + to -. The general swing you will see is about 2-3v AC, so set your meter on AC.

From here, you need to dig out the schematics, and work your way backwards through the circuit to see where you are loosing your signal.

This is just a basic overview, Troubleshooting the AVG, and Mathbox circuits requires more time, and testing tools.

Often times, I see boards that have been stacked, or just laying around and they will often have cut traces from rubbing against other boards, or broken components, and chips.

The Aux boards, have ALU chips on them, these get pretty hot, and are prone to failure. Also there are 7-8 custom proms on Aux boards for Tempest, Battlezone and the like. Any 1 of these having a dead output will cause a game not to run. These chips when you can find them Run $10-$20 each depending. You will find that the proms will tend to have black legs from oxidization. I use either a pink eraser to clean them, and will even soak them in Tarn-x and run a toothbrush on them to clean the legs.

Again these are just basic troubleshooting guides, once you have a game that is running, you can get more in-depth on a particular section that is not working right. Ie highscore not saving, sounds missing, button inputs not working.

Hope this helps.




This post really helped me fix my BZ game. I was going in circles and decided to remove the Braze technologies little plug in board. Put an old CPU chip I had from an old board and the machine came back to life.
I seem to read a lot of people having the same problem. Spot killer and led lights all on. All voltages seem correct but no picture, sound, nothing. There was no voltage at all from XYZ test points. [ not sure what this should read ]. I'll test the XYZ again now that its working to compare.

Great place for help....thank you
scott
 
Hey, i just noticed you have a star trek upright and board repair experience, any chance you can troubleshoot my new star trek board set?

MikeRK specializes in that. I believe that DouglasB does that as well.
 
Here's a quick video I did tonight on how to crimp replacement ribbon cables.

It's easy to do and all you need is a 4" bench vise with padded jaws and a very sharp knife. I use a utility knife with a new blade and it cuts the ribbon cable cleanly.

Enjoy!

 
PCB power questions.

1.) How come boards have edge connectors with multiple inputs for the same voltage or ground? For example, pins 1, 2 and A&B on the solder side are +5V, while maybe pins 16,17,18, T, U, and V are all ground?

2.) Say I want to test the board on my workbench with a switching power supply. Can I run an alligator clip from the +5V to one of the edge connector pins (assuming parts/solder side are both +5V), so do I need to supply feeds to ALL of the edge connector pins with that value? (Same question for ground).

3.) So I have a two board set that is not working, at the very least, because of a 5V voltage drop. How does one tell if the voltage drop is due to components on the boards or due to a power supply issue? In other words, is it possible for the power supply to be putting out proper +5V, +12V, etc... to the edge connector, but fail to deliver that voltage once connected? What if the voltage drop is due to crummy edge connectors themselves? What is the correct process to diagnose the source of the problem?
 
> 1.) How come boards have edge connectors with multiple inputs for the same voltage or ground? For example, pins 1, 2 and A&B on the solder side are +5V, while maybe pins 16,17,18, T, U, and V are all ground?

Because some boards require more current than can be safely passed through 1 finger on the board. There's also some redundancy built in when you have more than 1. Who knows, maybe there's a board out there that doesn't tie all 4 fingers into one +5v line and uses them separately? Best to give it whatever is there.


> 2.) Say I want to test the board on my workbench with a switching power supply. Can I run an alligator clip from the +5V to one of the edge connector pins (assuming parts/solder side are both +5V), so do I need to supply feeds to ALL of the edge connector pins with that value? (Same question for ground).

I wouldn't feel comfortable using alligator clips on the end of a board. Some alligator clips squeeze hard and have jagged edges. Maybe you can get away with it but I wouldn't do it on one of my boards that I cared about.

I would personally grab the correct shell to mate with the board and load the correct pins into it and use that.
 
GORF board issue

Maybe you can steer me in the rigt direction.....on my Gorf game, the game is fully working...but the space invader guys on the firstvlevel leavecdotted trails, or lines behind them, left to right...the lines remain on all screens....is this a ram issue, or a heat-damaged chip on the cpu board? Any help is appreciated! Jim. [email protected]
 
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