I was once at a church rummage sale, and there was a box with a Thorens 145 in it. Written on the box was, "Platter missing." It was ten bucks, so I knew I could part it out and make money, so I took it home. In those days I made a little money buying and selling turntables. Anyway, I was taking the pieces out of the box...and there was the platter! I sold it for $150, one of my better turntable resale scores. What I kept was a Dual, and I don't remember the model #, but it had the ULM arm.
The ADS tuner is great, and I still have it. The mono amps went bye-bye in a swap, but I got the short end of the stick. As for Proton, it was separate from NAD, but both were made in the same factory in Taiwan, so that made the resemblance.
Yes, sometimes used gear can be a money pit. Here's a story of two amps:
1. The Arcam Delta 60 - bought from a pawn shop, and there was always something wrong with the gain pot. I finally removed it and installed a new Alps unit which even had the same stock number as the old one. It meant losing any balance control - the old one was dual-concentric - but it works now and sounds great...twenty years later.
2. The Cyrus 2 with PSX - another pawn shop purchase. I sold the Cyrus tuner, and waited years to get the amp f$i$x$e$d. It still sounded Not Quite Right, so I recapped the preamp section with good caps, and it was soon sounding great. Sadly, not so long ago, I plugged another component into power with the Cyrus live - there was a thump, and then nothing.