Yes, if you are restoring and you have the time/money available, DO IT. Worn caps will definitely affect sound quality. If they fail, they can cause acute symptoms and features may fail to work. Shorted or open caps might even cause failure of that channel. Worn caps that haven't failed yet, but are out of spec, have excessive ESR, etc can alter the tonal balance. Worn or iffy caps also frequently cause motorboating sounds, whine, oscillation, and often can be the cause of generally unreliable mysterious gremlins. AS for the recommendation to find another boombox..... why? Moving from one 40 year old boombox because the caps are worn and it's too much trouble to change, so you can replace it with another 40 year old boombox that has, guess what, 40 year old electrolytic caps too? Take the time and the relatively small cost to recap the boombox and you can be sure it will hum along for another 40 years. And NO, you don't need an oscilloscope to troubleshoot caps. You can test them with an LCR meter but by the time you remove them for testing, you might as well put new ones in there rather than stuff the old ones back in there. Otherwise, a boombox that has 4 of the 128 el caps replaced with the rest of the originals still in it can hardly be considered "restored" can it? Better to consider it "fixed." "Restored" suggests a higher level of service than just testing to see if components are in spec or working.
