How do you check a PCB

[Taco]

I was wondering what steps you take for troubleshooting a bad PCB. What methods are used and where to begin. In "newbie" terms please.

I want to learn how to work on these boards because I sent my Cherry Master board back to Amcoe for the ( coin jam ) error, and they said it was only a dead battery. The board checked out fine. It's got me wondering about my Magical Odds board that reads the same error. The battery on it reads 1.6 volts and should read 3.6. I may just need to replace the battery?


Much Appreciated

Taco    Veteran

[stayouttadabunker]

From what platform?
What kind of machine specifically?
You'd better be prepared for a lot of reading once I find out! 

[Taco]

Cherry Master type machines. Basically you call them eight liners I guess?  I'm disabled and it gives me something to work on.



Thanks

Taco   

[jay]

Troubleshooting 101 begins........ Start with the obvious.... and ask yourself what changed ??? If it was working 5 min ago and now its not.... something has changed......
I am not sure that all my comrads here (especially the more technical ones would follow this path but it usually works for me).


The number 1 PCB problem is batteries. The machine forgets its memory and all of a sudden all of your options are no longer available. 
        The worst problem is a leaky battery that perhaps eats other components or raises traces off the PCB.

The number 1 "System" problem is power or lack there of.
        I always check my fuses with a multi-meter, then check my power supply output voltages. Amazing what the absence of +5 volts will do.
       Transfomers have a life, the large caps in a power supply have a life and take the most abuse from A/C line power

Getting back to the PCB.... if its not your power then look at where the power goes in. Since these are usually friction fit edge card connections corrosion is a common problem.
      I would use a white eraser and clean up these connectors on the PCB
      I also use contact spray on the contacts where the board seats  (sometimes called tuner spray as they used to use it on OLD TVs that had a manual dial - these rotational contacts got dirty and then your picture went to crap).
      Spray a Qtip and you will be amazed at the black that comes out.

Next I would turn that board upside down and give it a couple of good shakes and see what falls off. In an old cabinet no telling if a drop of cold solder or other such metallic bit (coin, gum wrapper etc ?) has fallen onto the board and shorted something out.

Post this point I would put the board back in and give it a go.........

Next I would pull every socketed chip out, look for dirty pins, clean with eraser or contact spray and reseat.

Post this point I would put the board back in and give it a go.........

Next would be closely examing the board (and smelling it) for burnt resistors. A magnifing glass and bright light helps regardless of age.
        You should be able to read the resistor bands. Just because there are hot spots around the resistor doesn't mean its bad but upon close examination on this part of the board you will sometimes see where a trace has lifted and broken

Depending on the technology of the board there are some chips that have a built in battery (I will let others elaborate) that when dead basically you need to change the chip. These I don't think are made any more but there are replacement chips in which you then jumper power over to one pin or something to that nature.... (this is where I am out of my league).

There are also a series of video games that have a kill circuit, I think both Centipede and Frogger - so once someone has beaten the game its over. Again there are hacks to replace certain chips.

Channel Maniac is really the guru on this topic so I suggest you look at his many threads on arcade repair.






     

[a69mopar]

man that's a lot of typing Jay,   I was just going to say to change the batteries.  They are obviously low.

W

[stayouttadabunker]

Jay's been copying & pasting that same post for about 10 years now...LOL
Just kidding...awesome post dude! 
That's a very good primer for checking out boards if I've ever seen one!

[TZtech]

Not related to current problem but may be of some use

Electrolytic caps - especially those found in power supplies and monitors. Check for bulges on the top. If in doubt shotgun (Replace them all even if you dont know which specific ones are faulty. If you are going to get more involved in repairs invest in a ESR meter.

Ian

[stayouttadabunker]

Here's how to make one if you don't have a lot of money>>>

http://ludens.cl/Electron/esr/esr.html

Also,
Some links for those who DO have money to spend...LOL >>>

http://members.ozemail.com.au/~bobpar/esrmeter.htm

Here's a little info on them>>>

http://preher-tech.com/esr.aspx

[Randy0777]

Great reply Jay  I talked to Taco on the phome and fixed his first problem  Last time I talked to him,he changed the BV and was getting a "coin jam" . This was a week ago. Sending my info now,sorry for the delay 

[Randy0777]

Taco,I sent you a PM...
Just a bit of advice 
Your talking about the same board,just different problems. Keep everthing in one post .
Not only will it help you to solve your problem easier,it helps someone six months from now looking for the same thing .

[Taco]

Ok sorry guys..will do from now on.

Just bought a new multimeter,soldering iron, ect..  I'm not sure that's a good thing....

[ROCKET]

Ok sorry guys..will do from now on.

Just bought a new multimeter,soldering iron, ect..  I'm not sure that's a good thing....

you will be surprised just how many little tools that you will purchase to fix arcade games -cherry masters etc
from mini needle nose pliers to the >>famous bent screwdriver >>mini straight blade of course <<<to pull eproms.
 
to the multi meter -jumper wires - spare batteries - mini screwdriver sets phillips & flat blade for the tiny screws --spare power supplies --boards that are termed junk -to steal parts from --the list goes on and on !

then comes the satisfaction & fun learning and making a dead machine come to life !!