BEC Posted April 22, 2004 Share Posted April 22, 2004 I have been meaning to post this for quite some time. This is a real easy tweak and everyone should do this one. First some background. I was a ground radio repairman as a young Airman in the Air Force back in the 60's. I was stationed at Altus AFB in Oklahoma taking care of the old radio transmitters and receivers at the RAPCON (Radar Approach Control). Anyway, all the transmitting and receiving equipment was 20 or more years old and quite a problem to keep running. There was rack after rack of terminal strips where cables terminated with ring lugs under screws. Many cables carried mic signals to line amps and from those amps to transmitters. A like number carried audio from receivers to line amps then to headphone jacks and speakers. Often a problem with noise on one of these lines or low volume or just erratic operation was fixed during troubleshooting without ever finding what fixed the problem. Just on a hunch one time, while troubleshooting one of these problems, I decided to just loosen and retighten all the screws at the terminal strips instead of pulling out all the equipment to do a bench test like I would normally do. Problem fixed. Then I went through all the cabinets loosening and retightening screws and after that, reported audio problems went from daily to infrequent. Best guess is that a film of corrosion products build up over time between the screw, the lug, and base of the terminal strip. Loosening and then retightening causes the screw to take a new "bite" into the metal. So just go over to your old crossovers and loosen each screw on the terminal strip and retighten them. I took a break during writing this to see if I could measure the effect this has on resistance. Picked up an original Klipsch Type B3 that happens to be in the shop right now. I took measurements of the DCR across each terminal of the terminal strip from the screw on one side to the metal of the terminal lug connected to the other side of the strip. Worst number on that one was 0.7 ohms and best was around 0.2 ohms. I then loosened each screw about 1/2 turn and then retightened. Measurements were pretty consistently around 0.004 ohms on all terminals after that. Low numbers are good here, by the way. This is a cheap (free), quick (less than 5 minutes), tweak and may make a noticeable difference in the sound. Bob Quote Link to comment Share on other sites More sharing options...
3dzapper Posted April 22, 2004 Share Posted April 22, 2004 If it's free it's for me!! Thanks Bob. Rick Quote Link to comment Share on other sites More sharing options...
BEC Posted April 22, 2004 Author Share Posted April 22, 2004 Rick, To put this tweak in perspective, I think the lowered resistance achieved by rewiring the speaker cabinet to change from zip cord to the finest big wires and that achieved from changing the wires from the amp to the speakers from zip cord to the finest speaker cables available would be a lot less than the improvement I measured on that crossover by loosening and retightening the screws. Bob Quote Link to comment Share on other sites More sharing options...
NOSValves Posted April 22, 2004 Share Posted April 22, 2004 Who would of thought hey !! I'm sure mine are fine since I have screwed them up so much ... oops I meant screwed with them so many times Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted April 23, 2004 Share Posted April 23, 2004 Wow, Thanks Bob. One thing that's cool about this is that you can and have measured the difference the tweak makes. Also impressive is that this little operation makes more difference than replacing the in cab wiring with audiophile quality wire. Interesting story on keeping the RAPCON up and running, too. Quote Link to comment Share on other sites More sharing options...
leok Posted April 23, 2004 Share Posted April 23, 2004 When doing the re-tightening, if you apply (per instructions) a little contact cleaner/lube (like Caig "Pro-Gold"), the tendency for corrosion buildup is significantly reduced, lengthening the time before the problem re-developes. Leo Quote Link to comment Share on other sites More sharing options...
fini Posted April 23, 2004 Share Posted April 23, 2004 Very cool, Bob! This seems like something even I could do! I am sure I have a few loose screws. Quote Link to comment Share on other sites More sharing options...
BEC Posted April 23, 2004 Author Share Posted April 23, 2004 What Leo said about that product may be correct, however, when perfect is considered to be metal to metal contact, putting "something" nonconductive between would be suspect. At least, that was the thinking on the millions of terminal strip connections at nuclear power plants. Bob Quote Link to comment Share on other sites More sharing options...
Parrot Posted April 23, 2004 Share Posted April 23, 2004 I once had a tweeter that I thought had gone out; actually the only thing wrong was a bad connection, and all it took to fix was retightening a screw on the crossover. It probably hadn't been reset in more than 20 years. Quote Link to comment Share on other sites More sharing options...
leok Posted April 23, 2004 Share Posted April 23, 2004 Bob, Good cleaner/lubricants do not interfere with the metal/metal contact. The cleaner helps to remove corrosion. The lubricant is pushed out of the way by the mating contacts, but remains on surfaces with air contact. These cleaner/lubricants are used widely in industrial and commercial low power electronic interfaces. A very effective application is on the mating surfaces of batteries mounted, in battery holders on pc boards, where corrosion is the more likely the cause of "battery failure" than any real problem with the battery itself. Leo Quote Link to comment Share on other sites More sharing options...
avman Posted April 23, 2004 Share Posted April 23, 2004 THANKS!!! dam!!! something ELSE to do 'in pursuit'...('82 cornwalls and '85 heresy 2's will be done first) avman. Quote Link to comment Share on other sites More sharing options...
Colin Posted April 23, 2004 Share Posted April 23, 2004 damn! something so simpl even I could do it -tonight! whne I get home! thanks! Quote Link to comment Share on other sites More sharing options...
BEC Posted April 23, 2004 Author Share Posted April 23, 2004 Leo, I agree. When corrosion is expected because of environmental or specific metal or chemical exposure problems, in nuclear power we would coat the terminals, usually with a certain special grease. The question about terminals not in areas likely to encourage corrosion has been discussed forever at nuclear plants. The idea of "proof" always comes up. It would take a 20 or so year test of terminal strips in different areas with and without treatment and to come up with this "proof". Resistance measurements using calibrated and tracable test equipment would have to be made to establish a trend. Just hard to focus the mind for that long and supply the money to obtain this "proof". Since the TDR (Time Domain Reflectometer) was developed in the late 60's by Hewlett Packard, a method has been available to "see" impedance changes at all terminations from one end of an instrumentation loop. I believe that TDR testing is probably in effect at all nuclear power plants by now to catch these termination problems before they become significant. I wish I could take some credit for the TDR, It is a wonderful technology. I can only say that I was in the Air Force stationed in Italy when HP came to our site and worked out how to build one. I was the first to use it, if that counts for anything. Bob Quote Link to comment Share on other sites More sharing options...
leok Posted April 23, 2004 Share Posted April 23, 2004 Bob, In the case of the battery example, with a product not in particularly harsh environments, field issues due to "failed battery" ceased once application of Caig "ProGold" became part of production and field service procedures. The installed base in this case is in the tens of thousands, so there is statistical significance to the before/after "failure" numbers. Leo Quote Link to comment Share on other sites More sharing options...
BEC Posted April 23, 2004 Author Share Posted April 23, 2004 Leo, I guess you would need to explain to me the protective mechanism you indicate is left on the terminal after application of the cleaner/lubricant. I certainly have no knowledge of your particular example of the battery on the circuit board and it sounds like you have good history on this one. I have, however, sat around several tables where the subject of some sort of protective chemical or lubricant is discussed for use on terminal strips. Honestly, I have never come down on one side of the other on this one, but the discussion is interesting. It usually goes something like this. Pro: "We should put something to prevent corrosion on these terminals." Con: "Why, when perfect is metal to metal." Pro: "Don't worry about that. When you tighten the screws, pressure and scraping of the metals remove all the product and you are simply left with metal to metal under the screw." Con: "Isn't that exactly what we would have without the use of the product." From here the discussion just ends. At least that is where it stood 10 years ago when I was still actively involved in construction. The facts would be that if the product prevents future corrosion, it and its nonconductive properties must still be in the connection. It it is not any longer in the connection, it cannot prevent future corrosion. Like I said before, I really haven't made up my mind on the subject and haven't been actively involved in this in 10 years. I mostly replied to Leo's post to see if I could hear a new argument in favor of use of protective chemicals on terminal strips. Bob Quote Link to comment Share on other sites More sharing options...
Deang Posted April 23, 2004 Share Posted April 23, 2004 In the case of the Caig products, they bond to the metal on a molecular level. At least, that is what they claim. Short of sanding it off with sandpaper, no amount of tightening is going to "get it out of the way" -- which of course is the idea -- because the goal is to create a gasless connection. The highly conductive liquid squishes into the places the metals don't, preventing future corrosion by locking out air, and also increases the contact surface area. The products are very good, and backed by some hard science -- and they ain't cheap either. On one hand I like the terminal strips because they offer low mass. OTOH I think they stink because the screws are prone to becoming loose due to vibration, and the already stated reason of being prone to corrosion. The best long term solution for connections is crimping or soldering -- preferably both. The best connection is a gasless one -- and this is the only way to make sure you get one. I know I know, I'm just a rookie. Quote Link to comment Share on other sites More sharing options...
Marvel Posted April 23, 2004 Share Posted April 23, 2004 I also thought that some of the corrosion comes from the mating of two dissimilar metals, even if slightly different. Anything in the air can act as an electrolyte, with the lesser of the two metals being corroded. This is what happens/happended on steel hulled ships, where the prop shaft goes through into the salt water. They solved that by using a lesser metal around the prop shaft that could be replaced when it deteriorated. Marvel Quote Link to comment Share on other sites More sharing options...
fini Posted April 23, 2004 Share Posted April 23, 2004 "The best connection is a gasless one..." I have seen enough of those "dating" TV shows to confirm this. "I mostly replied to Leo's post to see if I could hear a new argument in favor of use of protective chemicals on terminal strips." It's the fear of corrosion that sells 'em... Quote Link to comment Share on other sites More sharing options...
BEC Posted April 23, 2004 Author Share Posted April 23, 2004 Marvel, Perhaps "even slightly different" is is the operative phrase. All of us probably have had the experience of a bad connection at a car battery. Probably one of the most effective clamp connections we can imagine with a lead clamp surrounding a lead battery terminal. Yet even with a special grease coating applied all over one of those terminals to keep out outside effects, after a few years when you take one of these off, you find a lot of corrosion inside. Bob Quote Link to comment Share on other sites More sharing options...
Seadog Posted April 23, 2004 Share Posted April 23, 2004 Sounds like a great Saturday afternoon project. Just enough of a project to give me a good excuse to put off the yardwork for one more weekend! Quote Link to comment Share on other sites More sharing options...
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