Cleaning contacts

[K8WBL]

My Hunter 2000C amplifier's TR contacts need cleaning...this amp has not been used much and contacts appear OK, course I can't really see the surfaces unless I remove it...but what do folks recommend as an easy cleaning on these?  Don't want to use anything abrasive to errode the contact points any more than they perhaps already are. 

73, Tim K8WBL

[k3zrf]

try a white pencil erasure....works good on battery contacts also with no residue

[Jim, W5JO]

If they are not pitted and worn too much then a strip of a brown grocery bag will clean residue from between the contacts.  It is slightly abrasive and can remove light corrosion. 

Much more than that can shorten the life of the contacts.  If they are pitted then you really should look for a replacement because they will wear completely in a short time.

[WA1GFZ]

If they are silver and not pitted leave them alone or just run a bit of paper through them. Silver oxide is a better conductor than pure silver.

[ka3zlr]

WHAT I do, for Lite Problems,

I'm a paper bagger too, First I spray the unit down good, Then I Dampen the first piece with cleaner, alcohol etc, and clack the relays a few times moving the piece around to get some of the residue off, then I pull through a Dry piece a few times.

Years ago I used to Wet some relays with Mercury, But them days have passed, and besides today's warehouses have a pretty good choice for replacement.

73
Jack.

[WD5JKO]

The posts prior to mine pretty much covered it. I often have an unconventional way to deal with things, and what I will present has worked for me.

I once worked at a place where I was a bench technician and one item that would be on the repair shelf was a circuit board with a dozen PC mount 4PDT relays. The relays were partly controlled by a series of motorized cams, and this was all complicated by a massive amount of relay logic. A dozen relays with 8 contacts each (96 contacts total) lead to lots of confusion when the relay logic wasn't working. The motorized cam cycle was 4 hours long too, so failing meant another 4 hours.

I decided that troubleshooting was almost impossible, and wholesale relay replacement was too costly even though they were in sockets. These relay contacts were NOT silver.

The problem with those relays was the clear cellophane wrap around the relay coil would outgass when the coil was hot, and insulating material would condense on the contacts resulting in relay failure.

While remembering early 1970's CD ignition (recall the MSD-2?)failures that failed because the ignition "points" didn't spark and built up an insulating oxide, I built a test socket which used a pulse generator to pulse the coil about once a second. Each contact had a capacitor across it, about 10 mfd, and a series limiting resistor to limit the contact closed current to about 100  ma. When the contacts were open the caps charged up to about 12 volts. I then would look across the contacts with a scope one at a time to see how much voltage was dropped when the contacts closed. It was interesting that sometimes a given contact would pulse a dozen times before the oxide would break through and pulse by pulse increment down to zero volts when closed.

Building that test fixture was a lot of work, but after going through all 96 contacts that way, the relay board worked first time when ran through the test. The idea is especially useful with sealed relays that are not easily cleaned, or relays that don't have a readily available replacement.

73,
Jim
WD5JKO

[ke7trp]

Yep. Its covered.. But I use a matchbook cover (thin cardboard) soaked in Deoxit. I slide the cardboard between the contacts, Apply light pressure to the top contact with my finger, Then pull the paper in and out.  THis has worked for me many times.

Also.. Some relays will have multiple contacts and some are not used.  You can take the stack apart and flip the stack so you have new contacts in service.

Clark

[N3DRB The Derb]

the best contact cleaning paper in the world is a fresh new dollar bill. swipe just a bit of deoxit DN-5 on it and go to town.

[WA1GFZ]

would that be considered defacing money? Is it still worth 5 cents after you are done? Does sound like a good idea

[k4kyv]

I use an uncirculated $2 bill that I got fresh from the bank to keep the dit contacts on my bug clean.  Some old navy man recommended that and said he always kept one on hand just for the purpose.  The $2 note is better because they are rarely seen in circulation these days, and thus less likely to accidentally blend in with the spending money.

[KL7OF]

INTERESTING SIDE NOTE ON THE 2 DOLLAR BILL....Naknek, Alaska where a lot of people from europe and the old soviet countries come to work the fishing season in the canneries....A friend who is a bartender and liquor store clerk says that a large amount of american 2 dollar bills have showed up this summer.....They are in new condition and are marked with a 1959 date....the local bank has verified that they are genuine...Lots of contact cleaners around here....

[K8WBL]

Thanks all, I tried the brown paper bag strips and its working fine now.  What was happening was my receiver was cutting in and out and I traced it back to the contacts on the amplifier...i.e. pounding on desk brought the receiver back to life..hi hi for a few moments.....if this doesnt work I will go out to Rat Shack and get some deoxit, but hate to pay their price for a small, and I mean small spray can of that stuff.  Keep telling my self to buy a big can of it at Dayton each time I go but forgot...

Thanks again...this is a great site...

73, Tim K8WBL

[kc2ifr]

There is a product called a "burnishing tool" that I use all the time for cleaning contacts. It beats the sh*& out of all the stuff recommended so far.
It looks like a very small file but its very flexible and the surface looks almost smooth but its not.
Believe me this is the best u can use.
If u want I will send u one........they are cheap!!!!

Bill

[KD6VXI]

There is a product called a "burnishing tool" that I use all the time for cleaning contacts. It beats the sh*& out of all the stuff recommended so far.
It looks like a very small file but its very flexible and the surface looks almost smooth but its not.
Believe me this is the best u can use.
If u want I will send u one........they are cheap!!!!

Bill

Does GC still make them?

A few years ago I was given a couple Anvil tool cases, with partial sets in each.  VERY nice tools, all Cooper, XCelite, etc.  Between the two, there was 3 sets of complete tuning sets (the plastic tools GC sold years ago), and a few others. 

What I cherish is the handful of burnishing (Burmish I was told, but I'm probably wrong) tools that where included.  I've also found them sold as "points cleaners" at some swap meets, but dunno who might still sell them as that.

I also have a complete set of spline keys, for working on the Collins, etc. stuff.  Supposedly these where "sourced" from Ft.  Ord when it was closed, but who knows.  Lots of military #s on the tools, though, and ALL high quality.  The clown had 5, and gave me two

--Shane

[flintstone mop]

I use an uncirculated $2 bill that I got fresh from the bank to keep the dit contacts on my bug clean.  Some old navy man recommended that and said he always kept one on hand just for the purpose.  The $2 note is better because they are rarely seen in circulation these days, and thus less likely to accidentally blend in with the spending money.

I thought for sure Don would suggest a $3 bill. But $2 dolla is cheaper than $3 dolla

fred

[ke7trp]

I am not a fan of the burnishing tools. I have some. They tend to take off to much material for my tastes..

Clark

[K8WBL]

Bill, Clark,

That is my concern, taking off too much material.  This Hunter 2000C amp was essentially new when I bought it some 8 years ago...the guy bought 2 of them from and estate in Cedar Rapids, Iowa, where they are made.   I got mine for $300 as he stated it blew the fues every time he tried to power it up, he kept the one that worked fine.  When I got it, I checked all the HV caps and one was bad - just one of those things, bought new and was bad.  These were kits, like the Heathkit, but I think you could order them pre-wired, like my Globe Kings.  The TR contacts did not have that much use and they appear in good shape, just dirty and were intermittent on receiving.  My friend, WA8SDF is a big fan of DeOxit but I have none.  The brown paper bag seemed to work so I hope it continues to. Nothing more annoying than turning the QSO back to someone and then can't hear them..hi hi   Thanks again for all the advice. You guys have been life savers and helped me get my Globe King 400B going ...73, Tim K8WBL

[ke7trp]

No problem.  Order up some deoxit or other pro type cleaner. The cardboard/paper and Deoxit has worked for me everytime.

Enjoy the amp!

Clark

[w3jn]

I agree with Bill that the absolute best way to clean contacts is with the burnishing tool.  It's just a slim piece of steel with a very fine rough finish.  Western Electric made a kit - the 265C - for use in burnishing relays, contacts in telephones, teletype machines, etc.  So I woulnd't be too concerned about taking off too much material unless you get really aggressive.

However there are times you don't have the room, or use of the burnisher could damage a small finger contact such as a rotary switch wafer.  Best contact cleaner by far I've found is DeOxit.  DO NOT douche down the switch directly, wet a Q-tip and spread it around the wafer sparingly, then crank the switch around a few times to distribute it amongst the fingers.