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Author Topic: FL-2100 to Kenwood TS-940  (Read 842 times)
KB3KCJ
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Posts: 125




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« on: June 08, 2013, 10:06:09 AM »

I know it is probably good practice to use the ARB-704 amp keying relay buffer when hooking up a tube set to a new transistor rig.  I cannot seem to ascertain whether I need the ARB-704 to hook up the TS-940.  Some say always use the ARB704 in this configuration and others say it is not necessary.  Any suggestions would be greatly appreciated.
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KE3WD
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« Reply #1 on: June 08, 2013, 12:07:36 PM »

BING search engine, I typed in, "what is fl-2100 keying voltage?" and got the following: 

http://www.bing.com/search?q=what+is+fl-2100+keying+voltage%3F&qs=n&form=QBRE&pq=what+is+fl-2100+keying+voltage%3F&sc=0-30&sp=-1&sk=

The first return mentions a HIGH and NEGATIVE-going keying voltage. 

You must use the 704 or at least your own wired keying relay between that amp and any modern solid state rig. 

Trying to hook it up direct would certainly damage the radio's keying circuit components. 


73
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K2DC
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« Reply #2 on: June 09, 2013, 02:46:44 AM »

If you read the manuals carefully:

http://www.bcdxc.org/fl2100b_man.pdf
http://www.radiomanual.info/schemi/TS940_user.pdf

you would see that the FL-2100 uses a12V realy for keying, and that an interface is not required.  Just wire it up and go.

73,

Don, K2DC
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KE3WD
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« Reply #3 on: June 09, 2013, 07:37:32 AM »

The 'b' suffix is not what the OP wrote. 

This may be part of the confusion, don't know, but do know that the FL-2100 that I once had did not switch at the 12V level.  Perhaps the letter suffixes were part of a design change to accommodate the more modern rigs as time went on. 

One thing the OP can do, something I do as a matter of routine when confronted with a different amp to hook up, is use their DMM to MEASURE THE VOLTAGE ACROSS THE AMP'S KEYING INPUT. 

That way, you can quickly find out what the keying voltage situation is on that particular amp empirically. 

And since the amp is used, the measurement method would account for any user mods to the circuit that might have happened somewhere along the line. 

Or take the "better safe than sorry" route and order up and use that ARB-704, which, even if the amp's keying voltage was compatible or not, would represent a safe and easy hookup and operation in either configuration. 

But to snark about someone else not "reading the manual carefully" while ignoring that 'B' suffix identifier is rather interesting...


73
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K2DC
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« Reply #4 on: June 09, 2013, 10:43:31 AM »

For KE3WD:  Sorry, no intention to snipe.  And the FL-2100 you had may have been modified.  Here is the FL-2100 (non-B) manual, again showing a 12V relay:

http://www.radiomanual.info/schemi/ACC_PA/Yaesu_FL2100_user.pdf

73,

Don, K2DC
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KB3KCJ
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Posts: 125




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« Reply #5 on: June 10, 2013, 08:12:34 AM »

I apoligize that I did not indicate that the amplifier is FL-2100B and not just FL-2100.  Read and studied close and the negative keying voltages in the rig and amplifier are compatible.  Directly wired it and it seems to work fine with no overheating.  I still; however, appreciate any inputs.  Had the amplifier with a Yaesu FT-840 and make no mistake, you absolutely need the amp buffer in THIS particular situatin.  Thanks to everyone for your kind help.  It is all appreciated  Thngs seem to get a little rough when you get old and your hands shake a lot and soldering is necessary - hi hi.
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