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Author Topic: Burnishing contacts on Vibroplex bug  (Read 2730 times)
W3HKK
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Posts: 593




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« on: September 21, 2011, 01:08:16 PM »

I have  a 5 yr old red knob, chrome plated  bug that tends to make nice sounding dots for a few weeks then starts to sputter.  Ive tried to burnish the contacts with paper or cotton cloth and it seems to help for a while. 

Any suggestions on a better way to burnish the contacts for  cleaner sounding cw?
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VA7CPC
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« Reply #1 on: September 21, 2011, 01:39:48 PM »

Put some rubbing alcohol on the cloth, and pull it between the contacts as you _gently_ hold them closed. 

Those are solid silver contacts.  The greyish silver oxide is a conductor.  They shouldn't need "burnishing".

        Charles
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K3STX
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Posts: 960




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« Reply #2 on: September 21, 2011, 07:14:57 PM »

That is a brand new bug!! I don't have problems with mine that are nearly a century old.

Are you sure your contact is not moving around during the three weeks? Slight movement can make a nice "contact alignment" not so nice>> scratch dits. I clean my contacts with alcohol and sometimes if it seems really grungy I use metal polish (Maas) to rub off grunge to smooth it out. Take the contact arm off and REALLY clean that contact. I find the paper through the contact does little more than remove dust (I cover my keys with handkerchiefs at night to limit dust; it works!)

paul
« Last Edit: September 21, 2011, 07:17:03 PM by K3STX » Logged
N9GXA
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« Reply #3 on: September 22, 2011, 03:23:14 AM »

I use contact cleaner on a newer, crisp dollar bill. An elmer mentioned this to me years ago - The fiber-type paper does a good job.

HTH - Paul - N9GXA
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W5LZ
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« Reply #4 on: October 01, 2011, 07:52:26 PM »

One thing that hasn't been mentioned is properly shaping those contacts to start with.  They should be very shallowly convex, not flat.  That is NOT easy to do correctly, and a little bit goes a very long way.  As those shaped contacts are used they tend to flatten out a bit, especially softer silver contacts.  That usually take a fairly long time, but it happens.  If you change contacts, then that shaping has to be done again (unless the things have already been shaped, not too common).
'Burnishing' contacts means exactly what it says.  It definitely does NOT mean using a super fine file, or any kind of file.  A burnishing tool has no 'sharp' edges, only curved ones.  I don't think I've seen a real live burnishing tool in years.  They were much more common when higher voltages were applied to those key contacts instead of the low voltages/currents used today.  Those high voltage/current circuits caused pitting of the contacts which isn't very common at all now (same for relays, but that's more common today).
 - Paul
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WV4I
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« Reply #5 on: October 23, 2011, 06:11:33 PM »

Vibroplex sells a contact burnishing strip p/n 405 that works great on my Vibrokeyer.  Some of the other methods described may work just as well.
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