On Mon, 10 Dec 2012 12:42:56 -0800, Daniel Prince
wrote:
I cannot find my bottle of Tweek so I need to buy some new contact
enhancer. Which one do you use and recommend?
If you must, Cramolin, if you can find it. Caig red is you can't.
Or you can mix your own, as I've done (mostly for curiosity). Whatever
commercial product you select, look on the MSDS sheet for the
ingredients. Favorite cleaner mix so far is naphtha (Coleman camp
fuel) and a tiny amount of oleic acid (available on eBay). I don't
use a "contact enhancer" as I don't think it's possible. See below.
However, there's a problem. If you think about it, the idea behind a
contact CLEANER is to remove any oxide (or sulfide) coating on the
contacts. That's usually done with a weak acid, such as oleic acid or
vinegar. Both will eventually attack copper, so it has to be followed
by a water and alcohol rinse. However, that leaves the contact
material again exposed to attack by various aromatics, which will soon
return the contacts to their previous oxidized state. Enter the
contact preservative, which is just a coating of oil or grease. You
can do as well with almost any thin grease. However, note that all of
them are non-conductive, so adding grease increases the contact
resistance slightly. If allowed to mix with dirt, it becomes an
insulating layer, which makes things even worse than just dirty
contacts. Leave off the grease and high pressure contacts, such as on
some older rotary switches, will eventually gouge their way through
the plating material and expose the base metal, which will promptly
oxidize or tarnish. Of course, all this applies only to tin and
silver contacts, but not gold, which doesn't tarnish, oxidize, or
require lubrication. Wash with your favorite cleaner or solvent, and
leave the gold alone.
I have looked on eBay and contact enhancers come in liquids that you
apply with a brush, squeeze tubes, and aerosol sprays. Which form
do you think is best? Thank you in advance for all replies.
I use a syringe. The pressurized cans with the red nozzle usually
consume far too much lube and always make a mess, which is the plan so
that you'll use up the can quicker. With a small syringe, it's much
easier to get into tight areas, and dispense a controlled amount. I
have a small supply of medical glass syringes with *BLUNT* tips. Also
available on eBay). Plastic syringes with a rubber plunger seals will
work, but are eventually attacked by solvents.
More on cleaners:
http://www.antiqueradios.com/forums/viewtopic.php?t=82058&start=40
Drivel: In a past life, I used to design marine radios. Corrosion
and corruption (fungus growth) were constant problems. The
conventional wisdom was to select the contact plating correctly (i.e.
gold is only for "dry" contacts, silver if it carries power), and to
not give the crud anything to stick to (i.e. no lubes, oils, greases,
or goo). The contacts could look fairly oxidized and disgusting, but
as long as the fairly tiny contact surfaces were clean, there would
not be a problem. Standard procedure for factory repair was to hose
the exposed contacts (rotary switches and relays) with solvent to
remove the contact cleaner grease residue deposited by the dealer.
Coax connectors were another problem. Some brilliant marketing person
decided that filling the coax connector with "dielectric" silicon
grease would make it waterproof. That works, but it also put a layer
of insulating silicon grease on the contact surfaces of the connector.
No water in the connector, but also no connection. Cleaning out the
grease completely is difficult.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558