Basic Troubleshooting - Checklist

This checklist assumes you have a multimeter and other basic tools and an understanding of voltages and continuity testing.

Here are the basics you should check:

1. Did you change anything? It is not uncommon for things to fail after a change. If you can, revert your change and see if it resolves the problem.
2. Check the board. It may be there is an obvious component failure or physical damage that will remedy the problem. Look for bad solder joints. Use a microscope or magnifying glass to go over both sides of the board looking for physical damage.
3. Mains Power. ~~red:NOTE - MAINS POWER IS LETHAL - DO ALL THE INDICATED CHECKS WITH MAINS POWER DISCONNECTED!~~ Does the machine have Mains Power OK? Is the fuse good, and does the mains lead have continuity? If the fuse has blown, why has it blown, are there any obvious reasons for it blowing? Are there any obvious shorts? If there is a mains switch, like on the ST, does it work when tested with a multimeter? If the switch works, check it with a multimeter using the ohmmeter function to see if the switch has high resistance across the contacts. If it does, it should be replaced.
4. PSU Power. Using an artificial load if possible, check the voltage as delivered to the machine match the specifications for that machine. You will need to check the specifications of the machine you are working on and/or the schematics to fully understand what voltages should be present. ~~red:Don't forget, sometimes the heatsinks are live on PSUs, so you should avoid touching them whilst power is on.~~
5. Board Power. Once the mains and PSU are verified as good, or if you are able to use a bench PSU in place of the original, power on the machine and ensure that any LED indicators are correctly lit. If not, investigate why by using a multimeter and schematics to trace where the LED power should come from and why it isn't present. If power is good to the board, check power is present and correct at all components. The schematics and data sheets will allow you to determine what pins have what voltages.
6. Hot Chips. When left powered on do any of the chips get excessively warm to the touch? This may indicate a failure, but may require more advanced techniques. It is possible for failed chips to get very hot, so take care when touching or use an alternative means to check the temperature.

If you have worked through the list and still have a fault, then you may need more advanced troubleshooting techniques and knowledge to resolve your problem. This is beyond the scope of this article.

Advanced troubleshooting is something you have to learn, and something that takes years, not hours, to become proficient at. These techniques require that you interpret data you have in front of you and make decisions based on what you see. It doesn't always work, and you need to backtrack and look at things from a different perspective and with more data. It may also take a lot of time to get a result.

Advanced troubleshooting often involves more expensive tools such as oscilloscopes, which you may not have, and that means you will need to ask the forum for help. If you are considering buying an oscilloscope, great, but read this first: Oscilloscope Comparison

If you find yourself in this position, please understand that problems do not necessarily have a 'silver bullet' solution. By this we mean "If you do 'this', it will fix your problem". There are rarely 'silver bullet solutions', so be prepared to work with the people here who will try and help you.

This means:

1. Answer any questions you are asked with as much detail as possible.
2. Post pictures where relevant, be it screen shots or shots of the machine in question. Ensure the images you upload are high quality so we can see all the detail we need. If a photo is fuzzy/out of focus/too dark/too bright/too small then it will not help.
3. Be patient. Troubleshooting can take a long time. Remember, whilst most retro machines are not hugely complex physically, they are complex electronically.
4. If you are also asking for help on Facebook, you may get 10 different and conflicting opinions and rude replies. Try to stick to platform specific forums where it is easier to get a more balanced view of things.
5. Don't be afraid to ask on the open forum, rather than by PM. You might feel daft or stupid for not knowing, but we have all been in that position, and asking on the forum means all forum users can benefit from the conversation. If somebody on the forum is rude or denigrating, report it, it won't be tolerated.

Last but by no means least, good luck in your troubleshooting efforts!