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Author Topic: IC-706 Problem - radio shuts off on keying  (Read 8876 times)
N5MZL
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Posts: 38




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« on: July 04, 2014, 05:34:36 PM »

It appears I just blew up my radio, but I've never seen anything like this before.  I wanted to try out a Heil iC Handi Mic I have on the IC-706, using the same mic adapter cable I'd used with the Heil headset I had used successfully before on the '706.  The Heil hand mic had also worked fine on a IC-746Pro I used to have.

As soon as I keyed the Heil mic, the radio powered off.  I put the stock mic back on the radio, and now it does the same thing; key the mic, the radio powers off.

Pressing the power button brings the radio right back up, but shuts down again as soon as you key it again.  Also noted that this is not an antenna problem, since it does this regardless of whether the radio is on HF or VHF/UHF.

Any suggestions?

Thanks...
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KB4QAA
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Posts: 3256




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« Reply #1 on: July 04, 2014, 07:45:09 PM »

-Master reset
-Add choke with multiple turns of the mic cable close to the radio connection.
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VA7CPC
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Posts: 2805




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« Reply #2 on: July 04, 2014, 07:57:46 PM »

Even before adding ferrites (an excellent idea):

The two most-common causes of "shutdown on transmit" are:

. . . bad connections at the ends of the "remote" cable (between control head and rig), and

. . . high-resistance connections (especially corroded fuses) in the DC power feed.

So remove the locking screw (you _do_ have it installed?), pull the cable off both connectors, clean everything with contact
cleaner or alcohol (gold-plated contacts -- do not scrub with eraser!), and re-assemble.

Then do the same with the fuse holders and battery / power-supply connections.

.            Charles
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WB6BYU
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Posts: 17053




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« Reply #3 on: July 04, 2014, 08:15:51 PM »

The most common reason for those symptoms is that the voltage drops to the radio
in transmit mode.  This might be due to an undersized power supply, low charge on
a battery, poor connections in the cables, a high resistance fuse, etc.  Often you can
tell by connecting a voltmeter across the power cables right at the rig and watching
the needle as you key the rig.

But the first place to check is your power supply and cables.
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WA3SKN
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Posts: 6496




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« Reply #4 on: July 07, 2014, 04:55:38 AM »

How does it work when transmitting into a known good dummy load?
Then check both the voltage and the current at the board when transmitting.
Since you did not indicate a blown fuse, I would suspect a poor connection lowering the voltage below the required level for the radio... causing a shutdown.

-Mike.
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W4AKF
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Posts: 17




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« Reply #5 on: November 18, 2017, 11:00:04 AM »

I had the same issue....just started....was the power plug to the radio....cleaned and expanded the prongs a bit....problem solved!
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KD7RDZI2
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Posts: 217




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« Reply #6 on: November 18, 2017, 02:15:13 PM »

I have seen a similar issue with a modern IC-7000 in FM mode. It was due so some oxidation in the plugs of the DC fuses in the power cord. Take out the fuses, brush them, spray some isopropyl alcohol (be careful it is extremely flammable as it is pure alcohol) into the female connector and put the fuses in the connector again, wait until there the alcohol is completely vaporized. I heard over radio a couple of QSOs about this issue on other IC radios. Not sure whether this is an issue more frequent with Icoms.
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W5DXP
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« Reply #7 on: November 18, 2017, 08:28:36 PM »

I had an instability problem with my IC-706 that I was told is quite common. ICOM bulletin #928 describes the solution - adding a ground strap and cleaning some spring loaded contacts.
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AC4RD
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Posts: 1450




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« Reply #8 on: November 19, 2017, 11:30:20 AM »

I've had both problems with my 706 over the years; poor power supply, and that weird "instability on transmit" problem W5DXP mentioned.  Both are pretty easy to fix.  The power connectors you know about; the fix for the 'instability on transmit' thing (which simply shut my 706 off, every time) can be found on the web.  You'll be up and running soon. :-)  73!  --ken
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WA3SKN
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Posts: 6496




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« Reply #9 on: November 19, 2017, 01:46:11 PM »

2014 post.
But the answer here is to get it on a dummy load and to start checking voltages... you will usually find the problem.

-Mike.
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