I have a Sansui receiver, (glass tubes)that my dad purchased when he was in Korea back in 60’s while serving in the military.
I was getting lots of bothersome noise/static when adjusting volume, etc., some burned out lights on the unit, etc. I took it to the local high end stereo shop in Des Moines, Iowa (Audio Lab?) back in the early 90s to see if they could fix it.
The guy was looking at it as I commented that it was old, but very powerful, suggesting that if they couldn’t fix it, I could just replace it.
The technician flipped the unit upside to expose an attached sleeve on the bottom that I had no idea existed, and proceeded to pull out the schematics. As he spread this document out and looked it over he said, “we can fix anything wrong with this unit. If you should ever wish to replace it with anything having similar output, quality and capability, you’ll be spending between $3-4 thousand dollars.”
I still have that receiver, albeit in storage, as daily listening has been moved to a smaller Bang & Olufsen unit that takes up a fraction of the space.
That said, I have been unable to bring myself to get rid of it despite more than a couple of offers.
I bought a bunch of very high-end gear in 1977. I got rid of the Dahlquist DQ10 speakers, the Thorens turntable, and the Mark Levinson preamp (the first one he sold). But I still have my two Kenwood LO-7M power amps even though they are in storage. I had them rebuilt about 20 years ago because the capacitors go bad. But the power amp in my Anthem AV receiver is plenty good enough (especially for these old ears) and because I like low listening levels. Actually, I enjoy peace and quiet a lot more these days.