[Boatanchors] Corrosion on tube pins and sockets

[Donald Chester]

I have found that WD-40 works as well as or better than Deoxit and other contact cleaners.  NEVER spray it on; spray a little into a bottle cap or other small vial, and use a toothpick or loop of small gauge wire to transport a small drop to the contacts in question, whether  switch contacts or female receptacles in a tube socket.  You want to use just enough to wet the flaky contact and nothing else.  Phenolic absorbs liquid, and residue clinging onto surfaces like ceramic makes an excellent dust magnet.  WD-40 permanently repaired the noisy AF gain pot in my 75A-4, whereas "contact cleaner" would only temporarily quieten the noise for a few weeks.

The greatest problem I  have had with tube pin contacts is when tubes or sockets have lain for years on the shelf, with no tube in the socket or the tube not inserted in a socket, and the entire contact surface has corroded from humidity in the air.  My solution has been to first clean the tube pins with fine steel wool (never use sandpaper), and then wet them with WD-40 or your preferred contact cleaner, and then insert and remove the tube from the socket several times, allowing the tube pins to  clean the socket.  In  case of heavy corrosion of a socket, I  have successfully cleaned the clips by rolling a small piece of fine steel wool into a small roll about the size of a tube pin, and working that back and forth inside the clip and then twirling with a rotating motion inside the socket clips.

I once "mined" some VT4-C/211 tubes that I found completely buried in the ground in a room in an old house where the floor had rotted out decades earlier and the tubes, some still in the remains of their boxes, had fallen to the ground, then the decomposing, termite infested wood gradually turned into soil.  The bases and pins of the tubes were badly corroded, but careful cleaning and polishing with fine steel wool fully restored the pin contacts with no evidence of etching.  The aluminium tube bases remained pitted from corrosive minerals in the soil, but otherwise were OK. After cleaning, about 10 of the dozen of so tubes tested good as new and only a couple were weak or dead.  I use a 211 in my homebrew rig to drive the pair of HF-300s in the final, so that gave me probably a lifetime supply of spares.  To keep them from gassing up, I  rotate spares into the rig periodically.

Don k4kyv