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Author Topic: Help with Yaesu FT-840, has output ONLY in CW mode!  (Read 2223 times)
W4AJF
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Posts: 262




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« on: June 30, 2012, 06:04:03 AM »

Hi all, I am looking for help with my Yaesu FT-840, I am hoping someone is familiar with this specific problem and can advise. I have an FT-840 and it ONLY has output in CW mode. It has NO output in SSB, AM, or FM mode (it has the FM board.). Yes, I have done a reset, and the RF power control has no effect in AM/FM/SSB, ZERO output. The radio will go on to the TX mode it just has no output in those modes, only full output in CW. Receive is fine, S meter is fine, everything else on the radio seems normal.

Anybody familiar with this specific problem?

Thanks,

Adam Farber W4AJF
Woodland Hills, CA
adamf@eeco.com
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KA4POL
Member

Posts: 1978




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« Reply #1 on: June 30, 2012, 07:30:48 AM »

How did this problem come up? Can you try transmitting into a dummy load? What power supply are you using?
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W4AJF
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Posts: 262




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« Reply #2 on: June 30, 2012, 08:49:20 AM »

Received it that way, always test in to a dummy load, have 35 amp supply, that is not the problem.

Anyone out there familiar with what it may be?

Thanks to all who try.

Adam Farber W4AJF
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KA4POL
Member

Posts: 1978




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« Reply #3 on: June 30, 2012, 11:13:34 AM »

I'd start with the connection from the switches to the main unit. Loosen this connector carefully and reseat it.
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W4AJF
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Posts: 262




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« Reply #4 on: June 30, 2012, 02:52:26 PM »

Hi all, I got lucky, I was doing some reading on the Internet where someone said that if they had a  keyer plugged in then the radio normally has no output in the other modes so I figured the mystery lies in the key jack perhaps. I took out the main board that has the CW key jack and sure enough all 3 leads had cold solder joints, the jack was loose! I soldered all 3 connections and radio is working as it should

Thanks to all who replied.

Adam Farber W4AJF
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TANAKASAN
Member

Posts: 933




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« Reply #5 on: July 01, 2012, 04:44:57 AM »

OK, well first a hearty WELL DONE to Adam for finding a really obscure fault in his radio.

Now that we've got that out of the way..............

Please could someone find the engineer at Yaesu responsible for this then take him out back and shoot him? There is no reason on earth why either a) a keyer plugged in to the radio or b) dry joints on the key jack should affect SSB, AM or FM modes. This is either poor design or a programming mistake.

Tanakasan
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WB6BYU
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Posts: 13242




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« Reply #6 on: July 01, 2012, 07:37:12 AM »

The Drake TR-4 was the same way - if you had a key plugged into the key jack, it had to
be closed to transmit SSB. 

Boy, was that puzzling:  the key lead was too short, and only reached the jack when the
rig was right-side up on the bench.  So it worked fine when it was upside down, but not
when I turned it over (and plugged in the key lead, but it took me a while to realize that
was what made the difference.)  Of course, the circuit I was trying to troubleshoot was
on the bottom of the chassis...
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AC4RD
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Posts: 1235




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« Reply #7 on: July 01, 2012, 07:59:56 AM »

OK, well first a hearty WELL DONE to Adam for finding a really obscure fault in his radio.

Agree!  Well done, Adam!
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W4AJF
Member

Posts: 262




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« Reply #8 on: July 01, 2012, 09:04:11 AM »

THANKS GUYS!!  Adam W4AJF
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K0CBA
Member

Posts: 299




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« Reply #9 on: July 07, 2012, 08:52:23 AM »

"I have an FT-840 and it ONLY has output in CW mode."

Doesn't sound like a problem to me Wink
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