My game is broken, what do I do?

PCB problems and fixes
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davewellington
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My game is broken, what do I do?

Postby davewellington » September 11th, 2012, 11:40 pm

I have a fault...
See the following post :)

How do I learn to repair boards
Read the Repair Guide on the wiki. Read as many Repair Logs as you can. Womble's are especially good because he explains his process.

What gear do I need to repair boards
Suggested repair equipment.

Who repairs PCBs
UK
Forum Member VectorGlow (Wales)

USA
Forum Member channelmaniac
Ken Westerfield - irepairsega.com

Rest of the World
Forum Member Womble (Australia)
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davewellington
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Re: My game is broken, what do I do?

Postby davewellington » September 11th, 2012, 11:41 pm

I have a fault..
First things first, perform the basic diagnostics, checking the voltage, checking for broken traces and dry joints, and reseating eproms/ribbon cables. These checks can be performed with just a multimeter.

After doing this..

My board doesn't boot
For a game to boot, 3 major components need to be working - the CPU, System RAM, and the Program ROMs. Provided these, and the components in between are working and the right voltages are applied, the game should boot. Verify the program ROMs by dumping them with an EPROM Programmer and using romident functionality in MAME. Using a Logic Probe or Oscilloscope, probe the clock pin on the CPU and check for a healthy signal. Check the reset pin - when the game is booted, it will initially be set low, and then should stay high. If it is dropping low, the CPU is watchdogging, which signifies that the game is crashing. Check the OE pin on both the System RAM and Program ROMs. Check the address and data pins on all 3 components for healthy signals. If you find any unhealthy signals, trace back to see where they're coming from, you might just find an ill TTL with two healthy inputs and a bad output. The idea is to get a lead on the fault, and then work back to find the cause.

I have a graphics issue
If the game has a service mode, run any RAM/ROM/Diagnostics check provided - this can help give a lead on the fault. If a section of RAM/ROM is identified, probe that component, OE, Data and address buses. Attempt to trace back any bad signals to see if they originate elsewhere. If the ROM is socketed, dump it and verify it's contents.

I have a sound issue
The sound system is usually easy to identify on a PCB - it's the corner where all the capicators are.
If your PCB is producing no noise, with the board powered on, lick your finger and run it along the legs of the amplifier - if no noise is produced, you most likely have a faulty amplifier. Check the 12V rail before replacing the amplifier to verify it is powered correctly. If the amplifier is fine (noise is produced), work backwards through the components using component datasheets, tracing the audio output at each step. Some boards require -5V to power audio components, so check if this is required.

I'm going to post a thread..
Please specify what repair equipment you have so we can give suitable advice.
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davewellington
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Re: My game is broken, what do I do?

Postby davewellington » September 11th, 2012, 11:41 pm

Saving this spot :)
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Re: My game is broken, what do I do?

Postby emphatic » September 13th, 2012, 6:19 am

Great thread! :thumbup:
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Re: My game is broken, what do I do?

Postby MrSandman » September 13th, 2012, 10:12 am

Thanks for this!
Well written, nicely organized and interesting and helpful links :thumbup:
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