Form Brent Jesse' site:
Do NOS tubes have dark pins? Most of them do. The only NOS tubes that retained bright pins are those that were sealed in the original box, and then stored inside of a plastic container, or possibly in a larger box in a temperature and humidity controlled environment. Not many tubes received this kind of loving care 40 years ago. Only gold pins should remain bright no matter what the storage conditions. Most pins of miniature tubes, being usually made of a copper alloy, will darken rather like an old penny. This does not affect the operation of the tube. If you are a purist, cleaning the pins with a good grade of contact cleaner with a Q-tip is a good idea. Cramolin DeOxIt is an excellent product for this use. Heavy encrustation will create noise and of course should be cleaned. I don't sell any tubes in this condition as all of my tubes have been inspected and cleaned where necessary. I know of some tube purists who sandblast the pins clean, and this is fine too, as long as any remaining grit is cleaned away by contact cleaner afterward. For most of us, a gentle brushing with a fine wire brush followed by contact cleaner will rid the pins of any Nasty Old Stuff. Don't freak about dark pins. These tubes are antiques, and have not spent their time in airtight containers! Cleaning the pins (unlike cleaning rare coins!) will not decrease their value, and your hi-fi will thank you for the increased contact and socket lubrication.
