PCB Manuals

Arcade PCB Game Board Repair

Welcome to the Retro-arcades board repair page. On this page you will find a good basic overview of PCB repair, plus lots of handy tricks and tips to help you get that faulty arcade board fixed, also info on the tools you will need to get you started. You will also find a comprehensive list of aracde PCB board manuals. Need a schematic? Take a look in the list, your bound to find it there.

Tools for the job

  • Magnifying Lamp
  • Soldering Iron with as fine a tip as possible
  • Solder :)
  • Solder sucker
  • ROM/Chip Puller
  • Multimeter with continuity beep test
  • Logic Probe

Aditional advanced tools

  • Desoldering station
  • Oscilloscope
  • USB Eprom Programmer
  • Hewlett Packard Logic comparitor
  • ABI Boarmaster 4000
  • Fluke 9010

Checking for physical damage on your arcade board

The first thing to check for is physical damage on the faulty or dead pcb, these things were kept safe when secured inside the original cabinet, but were often taken out and mishandled by arcade operators, slung onto shelves or into boxes and damaged. Get yourself a good magnifying lamp or use daylight and a good magnifying glass. Check for any physical damage/cuts to the tracks underneath the board, use a multimeter on the continuity test function to check any suspected damaged tracks. Check for any loose or damaged components on the board. Carefully press on any of the socketed chips because they may have become loose! It really is surprising how many faults are due to physically damaged pcbs.

Other components on the board could also be damaged , resistors, diodes and capacitors. Electrolytics tend to age badly, look for smashed bent or bulging electrolytics. Any capacitor with white stuff at it's base needs to be checked, this could be leaking, or it might just be glue used at the factory to hold the cap down a bit better. Ceramic capacitors will be all over the board, they are small orange disks, they are decoupling caps and often look very battered. Unless one has gone short circuit, it is not likely to cause any major problems. Only look at these closely if your board randomly crashes or resets.

Checking the 5v Power

Power to and on the PCB is also one of first things you should check, check that a good 5 volts is getting to the chips on the board. Measure the voltage on the actual chips across the board, a small voltage drop across a board is normal, you may have a good 5V on the jamma edge but if that drops to 4.5V at the other end of the board then things could get weird. Any board voltage measurement should be taken across the ground and vcc pins as it's the best reflection of what the chips are truly getting. If low either increase the voltage slightly, or run a power wire to the far side of the board. TTL chips don't like voltages much below 4.8V they can do strange things below that. Check the power supply again, some older boards require their 5v to be more like 5.2V

Locating faulty chips

Finding faulty chips can be fairly simple or close to impossible, at the very least you will need a logic probe and the knowledge on how to use it. Obviously a logic probe is very good at visually showing you what the pins of an IC are up to. In terms of inputs and outputs it visually shows you if a pin is high, low, floating (tri-state), and therefore by definition a logic probe is excellent at showing you when you have either stuck inputs / outputs (pin stuck high or low) - a bad thing, or when there is a good amount of activity - probably a good thing. This might be normal though as some chips are dual, quad or octal chips - i.e. they have 2, 4 or 8 of the same logic gates on them, its not uncommon to find a quad chip where only 3 of the gates are used. The inputs to the 4th gate will be floating as they are not connected.

To check this out you will need to google and read the datasheets for that specific chip. If the inputs are active and the output is floating then you have found a dead chip. You can go one further here, if the inputs are active and the output should be doing something (based on the logic table in the datasheet) yet it never changes from low to high then you have a stuck pin, this gets harder to work out by eye the more inputs a logic function has. If you have 6 inputs that determine what the output is doing, and all of them are active and flipping then it can be very difficult to tell if the output should be changing at any given point.

RAM chips are a common failure, find the datasheet and check the address and data lines. If you find floating lines then you are on to something, follow those lines back and see where they should go. Something is dead somewhere, it might be RAM .RAM needs controlling tho, you need to check the chip enable pin is actually enabling the RAM, and the WR and OE lines are doing something, if these are dead the chip will sit there doing nothing.

ROMs, same as with RAM, the control lines need to be working correctly, check the output pins for signs of life. The contents of the chip will need to be checked too, for this you will need an eprom reader.. The game board could be in perfect working order, but a single error in an elderly ROM will cause the board to crash straight away. You could spend a long time looking for a hardware fault that doesn’t exist, if the problem is due to dodgy software. PROMs are like EPROMS but they are write-once chips. Contents of these chips can be checked against the roms in the MAME set, there are apps and romident websites to do this.

CPUs are very complex and can be virtually impossible to debug, if they are socketed it's easier to try the CPU in another board, or try a known good CPU in your board. If its soldered in and you can't remove it, then you will have to assume it works until you have evidence to the contrary. Find the datasheet and see what the address and data lines are doing, bear in mind that a stuck pin doesn't necessarily mean the chip is bad, a track on a board has at least 2 ends, if the chip on the other end is shorted then the chip at your end won't be able to drive that line, so you may have found a fault from the other end.

Sound and audio amps - Audio amps can often be dead on older boards, they are usually the only chip bolted to the board usaully via heatsink.. A quick test to check the 12V feed is to run your finger across the pins of the amp chip or across the pins of the volume adjust pot. You should here a crackle, if not then push firmly on the body of the chip (if it's firmly bolted or soldered down) you should here a buzzing noise. If you do get a noise then the amp chip is fine, especially if you can adjust the volume of the buzz with the volume pot. Bear in mind that the amp chip depends on the circuitry around it, often a cluster of capacitors, if any of these are damaged you may not get a positive result, even if the amp chip is fine.

Custom chips -Unfortunately these can be board killers. They are usually surface mount, and can have upwards of 50 microscopic legs, and often there is absolutely no way to test they are working correctly, even if you could test them, there is no information around these days about what they do. Swapping them is not an option as the only place you could possibly find a replacement is on another board of the same game and without the specialist equipment needed, there is no way to remove or replace them. If you have a dead custom chip then the board is scrap, it's simply cheaper to buy another working board.

It's a good idea to read as many repair logs as possible and familiarize yourself with the workings of the hardware your dealing with. Read on!

Handy Links

Check out the following list of links, they will definetly prove helpful and informative!