Computer diagnostic. How do they do it???

[Brayden_2]

How do some computer companies do diagnostic scans on a computer that will not boot. Is there such devices that are external that will scan the computer even when the computer is not booted. I'm not talking about the problem computer using a a diagnostic tool.

Are possibly another computer scanning the problem computer??? How do they do it? Or is it literally trial and error with swapping every single different component with one that is working in order or testing voltages with a voltemetre ect.

Thanks all!

 

[Finstar]

Usually it's just trial and error though PSU and Motherboard often get tested first. For PSUs there's a purpose built testers that test the voltages.

 

[Eximo]

I would say for the hardware, 90% part swapping, 10% visual inspection to identify the damaged part. With your typical end user it is going to be fan failure, capacitor failure (motherboard or power supply), or extreme dust build up. Hard drive failure if the machine is old enough. So usually a dusting and a motherboard/PSU swap solves most computer issues, maybe a new CPU fan or exhaust fan.

Real PSU testers are quite rare and expensive. Doing a quick voltage test doesn't tell you how it handles load, but will immediately tell you if one of the voltage rails has completely failed. (Most common failure I have seen is the 5V rail dying on OEM power supplies, interesting effect since the CPU still has power, mouse will still move)

Software troubleshooting these days is usually an off the shelf diagnostic program. Looks for and removes malware, viruses, and can make attempts to delete temp files and garbage in the registry. These sometimes work on your typical end user computer for common problems associated with casual use. Most places will just do a complete system wipe after saving off any files that might be desired if the diagnostic program fails to solve the problem.

When you charge people by the hour a horrendous fee it can be cheaper to just buy a new computer sadly. Basically, if it takes more than an hour, wiping it is the more economical option. You'll see all kinds of waivers you have to sign when you send a machine in for service.