Basic Principles of Fault Finding / Fault Diagnosis or if you like, Repairing Stuff -
First Steps: Observation > Confirmation > Disassembly > Re-confirmation
Observation:
- Before plugging the unit into the Mains or fitting Batteries a few basic observations should be carried out.
Check for any physical damage, ingress of liquids, infestation of insects, dampness, corrosion, arcing and the general state of the unit. Check the power cord for any signs of damage, cuts, burns, arcing - Basically ask the Question "can it be safely used to power the unit" If the unit is Battery powered are the batteries in good condition, the right type, corroded, flat. Use a fresh set of Batteries if in doubt. Check the Battery compartment for signs of corrosion, leakage into the unit and the condition of each battery terminal.
Confirmation:
- What is the fault, what should we be looking for.
Download or Consult the Instruction Manual and familiarise yourself with the correct operation of the unit. Confirm the description of the fault, is the fault related to the incorrect setting of the controls? Check other functions to see if they are also affected. If Mains and Battery powered check the operation on both power sources. Is there a Default mode, try defaulting the unit to factory settings. Basically try to gain an overall understanding of how the unit should correctly operate and what each control does and how it affects the fault you see. Write down what you see and what is faulty; if that helps you to remember later.
Disassembly:
- Take your time and clear and prepare your work surface, find a couple of containers for screws.
Remove the Power cord and/or Batteries. If the unit contains high voltages it may pay to wait 5 to 30 minutes for the voltages inside to drop down to a safe level. Identify and remove screws noting where each one went, just in case they are different sizes, lengths or types (Self tapping or Machine screws). If the case won't open or the covers won't come off, don't force them! instead check for hidden screws under a label or clips that may need to be released first. Try and remove covers without jolting the unit severely as if the fault is intermittent you may inadvertently fix the fault, which could make the next steps harder.
Re-Confirmation:
- It is important at this stage to recheck what you observed in the original confirmation of the fault. Because the unit is now open there are some extra considerations.
If the unit only connects to the AC Mains, powering it from an Isolating Transformer or RCD would be recommended for your protection. If Battery power is available think about just powering it from the batteries. Basically think about what dangerous voltages could be inside, is it safe for you and others around you like curious children or pets. Know your limitations and the limitations of any safety devices you use, like Isolation Transformers and RCD's.
Position the unit so there is plenty of room around it. Check again that it is safe to apply Power. OK? Now apply power and recheck that the original fault is still there. Did removing the screws or covers change the fault or is there a different fault?
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Any changes, additions are welcomed below