For electronics repair in the past a solder iron, signal generator, scope, multimeter, pliers, some wire, solder and some wrenches and screwdrivers were the ticket. Now with SMD electronics you need a special heatgun, solder sucker and a magnifying lens. And some good lighting.
The new oscilloscopes are quite the trick. They double as a multi meter too.
With the typical usb rack audio interface that is commonly found in music rooms in families... The plug/unplug habit that goes with usb can overvolt the connection chip. If that happens, (usually those circuits are very well protected) ,only the usb conversion chip and maybe a transistor will go bad. Swapping those out, in most cases, will revive the unit.
Mostly the owner is eyeballing another unit for quite some time and repair isn't something the person wants. But these types of projects are great for doing with family members just to see if it works. There is allways some family member or friend that would love the repaired unit. So it's great fun and usually an easy first repair. IF you can justify the purchase of said tools offcourse.
Back to the oscilloscope. This OWON HDS242 is such an new mobile oscilloscope example. ( I am still studying all the new offerings). These units come with a pouch ,measuring leads and they vary in batteries they use. There is the choice (price point of their varying sensitivity. Still have to delve into that.
The HDS2202S has a function generator, two channel and is 200 mhz and 300 euro. The HDS242 is 40 mhz and 170 euro. So do I wanna drive a volkwagen rabbit or a Mercedes S class. Well... I am undecided.
With these repairs.... The internet is your best tool. All the components inside a electric device have a code on it. If you type the code into google a spec sheet and where to order will pop up. Now you can measure and order a replacement if the measurement is out of spec.
Some repairs will become too costly. That's why I purchase the gear I am purchasing now. I now (after they arrive) will have 4 converters. I can measure the good ones for good specs and if one is unrepairable it will have parts for the other units. While these units get older more tutorials of how to repair will pop up.
Another tool for repairs that is fairly inexpensive but very handy to have is a capacity meter or... another word for the same thing: a transistor meter.
https://www.amazon.com/diymore-Trans...s%2C202&sr=8-5
https://www.amazon.com/YIHUA-Solderi...s%2C162&sr=8-6
Solder wick
https://www.amazon.com/VOTCT-Solder-...zcF9hdGY&psc=1
I hope this gives an overview of what is needed (usually) to repair current SMD electronics.
It will all pack in one suitcase meaning it won't take a lot of space and a full desk with big bulky specialized measuring devices. If you repair two or three mobile phones with it the gear has paid for itself.