Mike, Rob is spot on about computer repairers, I haven't come across a single one with electronics theory, it is simply a case of repair by elimination and past experience with similar symptoms.
Concerning VCR repairs, at less than around $100.00 labour per repair, it wouldn't be possible to remain in business when you consider what it costs to maintain business premisses, many types of insurances, advertising, wages, holiday pay, sick pay, long service leave and compulsory staff superannuation. Tube type TV's generally aren't worth repairing now because replacement cost is so low and flat screens, LCD and Plasma are, with few exceptions like computers, board replacement only because no circuit details or individual parts are available for the complex power supplies and PCB's.
To replace the power supply in some flat screen sets can produce bills of between $600.00 and $900.00!, 42" SD sets can be bought here for $1000.00 so, after perhaps five years, it isn't hard to see why the customer would opt for a new set.
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