Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: WWII Key Set Up ?  (Read 577 times)
K9BAG
Member

Posts: 22




Ignore
« on: September 19, 2009, 01:03:26 PM »

Hi fellows,
Recently got a fine Jap WWII Navy key from the 40s. Might be unused. It has 3 binding posts, contacts for up and down key. However the down key ohm reading is never zero, maybe 10 Ohms. I ran newspaper thru contcts and no change. They were clean. So any reason for the slight resistance on keydown?
Thanks - Peter
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #1 on: September 20, 2009, 07:32:15 AM »

If, after careful cleaning of all bearings as well as the contacts, it might indicate that the metal itself has a resistance.  You could use your ohm meter on the X1 scale to measure across the parts and maybe be able to tell that.  The Japanese in the WWII era weren't building super radio equipment IMO, having restored some long ago.  Was a real eye opener.  

10ohms resistance likely wouldn't make any difference at all to the kind of keying circuits in use in that day, either.  A lot of them had plenty of voltage potential at the key jack, another eye opener.  Can you imagine trying to work with a xmtr like that in the humid jungle climate?  Ouch.  

Still, you should try the key as it is on a modern xcvr, for the 10 ohms is not likely to stop the thing from keying.  

Have Fun.


--KE3WD
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #2 on: September 20, 2009, 08:11:11 AM »

Oh -- and is there a cable attached?  The wires in an old attached cable could be the culprits as well.  

Steel plus nickel and a few other metals often yields a higher resistance alloy, whether used in wires or in key parts, there are also the various so-called "pot" metals that may or may not come into play here...
Logged
K9BAG
Member

Posts: 22




Ignore
« Reply #3 on: September 22, 2009, 07:22:03 AM »

Fine, WD...No connecting wire used, measured at contacts. The back contacts give a zero reading. Odd to watch the meter dither between 20-6 ohms on key down on the front contacts. Used stiff paper under the contacts, no change. Will try it with the keyer for effects there, maybe not an issue.

--Peter
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #4 on: September 22, 2009, 06:47:13 PM »

>>Odd to watch the meter dither between 20-6 ohms on key down on the front contacts. Used stiff paper under the contacts, no change<<

That sounds like corrosion or other dirt on the contacts.  

Perhaps the stiff paper is not enough.  

Don't use a file or anything like that, try a cheap calling card that has a rough surface.  They have clay embedded  in them that is abrasive.  

I once polished a really corroded set of key contacts on a Lionel key with a piece of Scotch Brite because there was something on those old contacts that the typical burnishing wouldn't remove...   If you do that, be very careful, just enough to establish the good ohmmeter reading and stop.
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #5 on: September 22, 2009, 06:49:18 PM »

It might not be at the contact surfaces.  

Check carefully for continuity path, which may be through bearings that need cleaned.  

That moving ohmmeter reading leads me to believe that it isn't the alloy of the metal or anything like that, it has got to be a moving or mating surface connection problem.

Good Luck
Logged
K5LXP
Member

Posts: 4536


WWW

Ignore
« Reply #6 on: September 26, 2009, 06:51:12 AM »

Use that ohmmeter and *prove* where the resistance is by measuring each component of the key, before you grind up the contacts or otherwise wreck something else.

Mark K5LXP
Albuquerque, NM
Logged
KK7KZ
Member

Posts: 464




Ignore
« Reply #7 on: September 26, 2009, 10:10:50 AM »

My German Junker Key has a choke built into the base and in series with the front contact which causes it to read several ohms resistance. Don't know if yours has that feature....

-R.
Logged
K9BAG
Member

Posts: 22




Ignore
« Reply #8 on: September 29, 2009, 06:29:24 PM »

Good idea, Mark. I metered each part in the key circuit. Odd, all checked near zero except the contact on the armature. Was able to unscrew it but found nothing suspicious and  no pitting. Saw a coating on the 1/8IN contact, like solder. Ohm meter from screew threads to tip showed the resistance of 12-8 ohms. So I recleaned it on news print and set it up. It seems to key the tx okay with that minor resistance still. The key feels good with a long arm and solid feel. A keeper.
Thanks, fellas -- Peter
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!