I think there's a major difference in mechanical engineering components and electronics, ie TTs and tonearm vs electronics, not really much to go wrong with a well designed and manufactured turntable or tonearm for the most part, though there's always exceptions. Cartridges do wear out and either need to be rebuilt or replaced (stylus on MM).
Electronics to my mind is a different ball game, lots of little components that can fail so whilst it's great if you know a competent engineer or repair tech I would think it takes a fair bit of skill and knowledge to even diagnose a fault let alone repair it. An example, many years ago I had a Creek 4040 integrated amp, it went up in a puff of smoke, I rang the insurance company and the repair tech came out to my house, he picked up the amp and said " oh that's heavy, never seen one of those before, we mainly replace TV screens that kids have smashed with their Wii controls, I'll take it back to workshop and have a look" next day I get a phone call, " had a look inside your amp, it's buggered, I'll notify the insurance company "
There's electronics.... and there's electronics! Your Creek 4040 would be a piece of piss for me to repair for example.
Digital and analogue electronics are completely different animals, to my mind as different as electronics and plumbing are to each other! Many EE's did as employers expected and basically "went back to school" to learn a new trade to go alongside analogue, I choose to specialise in analogue as I simply had no interest in digital whatsoever and there will always be a need for analogue alongside digital.
With analogue in lets say a power amplifier there may be "only" say 8 transistors per channel alongside the associated resistors, capacitors etc BUT any level from a millionth of a volt to tens of Volts at similarly wide ranging currents and frequencies will be present at all points of the circuit and one can easily access those points and connect up test gear, analyse what's going on etc.
With digital there is only on and off, 1's and 0's, often no (or very few) resistors and capacitors etc but a million transistors all on an IC the size of your thumbnail and only the actual inputs and outputs etc accessible...
Unless you are say the Sony Corporation and making the IC's alongside £100,000 a go digital analyser specifically to diagnose that IC in the factory then the chances are that the best you can do is get to a point where you can say that on balance of probabilities the fault lies with IC 123... you can only really diagnose by replacement, maybe costing £30 and hard to get, and go through the incredibly fiddly process of replacing the part using SMD re-work gear costing a fortune and all under magnifying lenses etc. Often you could be no more than say 70% sure that the fault was indeed with this IC! If it then still doesn't work I can't not charge the customer say £100 for having changed an IC that had nothing wrong with it!
This is the nub of why so many high tech digital items are destined for the skip....
I'm already having to turn away maybe 1 in 3 ish of repairs because when I google the item and see that it is all SMD and under microprocessor control it is clear that the repair will be a right PITA, at least 2-3 times as expensive as fixing a trad made unit and I can't guarantee that it can in fact be repaired... but would have to charge for attempting it... Hence I'll turn that job away and take on the Sugden A21SE or the Quad 306 etc that I've also had an enquiry about fixing... That's how it's increasingly going... and the vast majority of repairers will be doing the same as me
With such equipment as the high tech item described the only practical repair is to obtain a complete new main board from the manufacturer and fit it... which they often refuse to sell you and it it is probably only available for 5 years after the item ceases production anyway... or the new board costs way more than a working S/H unit anyway rendering it an uneconomical repair.
I guess there's a parallel with modern cars... Once upon a time a shit hot independent OMB/SME automotive engineer could take on anything from a Mini to a Ferrari safe in the knowledge that the basic principles are all the same and they have 35+ plus years of experience and knowledge to draw on in repairing it.
Today unless you have the £30K BMW main dealer only diagnostic computer and access to all the digital management codes etc etc then it doesn't matter how many cars you've fixed before... you're stymied.
