I have a National NC183R rack mount receiver waiting for repair on my workbench,, along with a Telectro built TS-382F/U Audio Generator that are both older than me. Want real fun? To keep the TS-382F/U looking as original as possible, I remove the oil filled bathtub capacitors, unsolder the lids, and put new caps inside. Solder the lid back on, and put them back in. It is a military version of HP's original 200 series audio generator.