Here is my point of view:
By all means, follow the basic principles that you have learned. Your success is much more likely if you understand how the device works.
I can't speak directly, but probably the best idea for becoming a Certified Electronics Technician is to look into ISCET (International Society of Certified Electronics Technicians).
Rumors and folklore sometimes suggest that you should replace the component according to what they say, if you find almost the same symptoms, in many cases, this often results in "misunderstanding". This information is sometimes true, but it is not the way to become a competent technician.
My personal opinion is that you need to know when to 'let go' of a hypothesis about what is causing the problem.
Troubleshooting is a specialized field of science and has its own special views on some things.
Product testing and troubleshooting are different things. You may be the first person to power a device, and it has never turned on before. If the assembler is not of the highest quality, then you will get strange symptoms on your device, such as short soldering or corrosion, for example.
A variable toroidal autotransformer (However, most people are more familiar with the brand name than the component type, Variac for example) is invaluable for troubleshooting circuits that have many turns of power cable and are powered by an AC line.
Variable Toroidal Autotransformer
At that time, all the devices did not work at all, say, only half of the AC input. At that time, I was repairing a bad Amplifier which power supply was only 70 volts, no signal and no load. Unfortunately, the price of Variac and the like is very expensive, based on some sources we got! If you have the 2nd item, check the undamaged windings. You may need to replace the "knob" and its casing. If the knob is stiff, try using contact cleaner / control cleaner / lube, because that equipment was a miracle for me, at that time.
Learn how to operate a scope and why you do it the way you do. I suspect most technicians don't really understand scopes. Learn from a trusted source!!
Learn to use digital multimeter and analog multimeter, the analog one is easy to damage, if you don't know how to use it. But the analog multimeter indicator is the best to use.
Learn to use generators and use triangle output too!
Learn how to solder! Solder is not adhesive, but a metallurgical bond, according to some sources I trust, this is only for gold.
At least! if you really want to learn how to solder, NASA has developed a training program that will make you realize that your soldering skills are still disgusting.
From: Nicholas Bodley ( nbodley@tiac.net ).
Waltham, Massachusetts