[ICOM] IC-756PROIII No Transmit

Thu Jul 16 17:40:43 EDT 2009

My 756ProIII is back at the Icom America Bellevue Service Center for the 
second time. This rig was purchased in November 2008 and should still be 
in warranty.
It was returned to ICOM in March 2009 for no transmit, no power out in 
any mode. ICOM replaced the following parts. They only list the part 
numbers, not the actual devices so I can't be sure what exactly was 
replaced. There were no notes, no repair description or phone calls 
about the problem, it just turned up when a FedEx driver rang my door 
bell. Part numbers are 1110006430, 1750000581, 1750000851,and 
1530003091. I was later told they are the T/R switching diodes on the 
control board.

Now it is back at ICOM for a different problem. The rig was on, I saw a 
spot for someone I wanted to call, and when I keyed the mic (SSB) I had 
a steady carrier at more than the normal 100 watts output. I tried all 
bands and modes. With no CW key or mic connected, no matter what 
mode/band was selected, the rig put out a 100 watt plus carrier. I am 
assuming it is some sort of harmonic oscillation.

I received a call from Icom asking how I wished to pay $213.00 for the 
current repairs. I told them it should be under warranty but was told 
the failure was caused by ESD and not covered by the warranty. They said 
they would get back to me.

I only have one antenna connection to the rig from a LDG model DTS-4 
antenna switch. There is a Force 12 beam at 55 ft, a sloper, and a 
vertical connected to the DTS-4. When I shut off the rig I also set the 
DTS-4 to GROUND ALL which grounds the antenna jacks. I also turn off the 
power supply. I have PolyPhaser coaxial protectors on all coaxes where 
they enter the house, grounded to a ground rod professionally installed 
by the company that installed my tower. With all my antennas grounded 
and the P.S. turned off how would I get ESD to the rig? Also, ESD to me 
is what happens to your receiver front end. The receiver worked FB on 
both failures, it was the transmit function that failed with two 
separate problems. I live in Las Vegas. We don't have rain or 
thunderstorms here. I do realize there can be static in the air, that's 
why the USCG C-130's I flew in and worked on had static discharge wicks 
on the trailing edge of the wings but I don't think I have that kind of 
static in the air to effect a stationary antenna at 55 ft. There are no 
transverters, CVI devices, etc, connected to the rig.

I have now received a return call from the Icom tech who is doing the 
repairs. The first phone I received was from the billing department and 
they were not able to provide me with the technical reasons why they 
believe my failure is due to ESD and not covered by warranty. I am told 
that is again the same T/R switching diodes on the control board that 
failed supposedly from ESD. It seems I better check the grounding 
operation of my DTS-4 ant switching box and outside ground connections. 
I was told that just disconnecting the ant from the rig is not good 
enough, that the static charge can stay in the coax (capacitor effect) 
and then you reconnect the coax to the rig you will destroy these 
diodes. The coax must be grounded while disconnected. The Icom tech 
tells me he sees a lot of these failures from dry states such as mine, 
NV, as well as AZ, NM, UT, etc. where there can be dry static in the air 
without a storm. So what are you supposed to do? I am a contester. I 
can't have my ant coax grounded while I am in a 48 hour contest. If Icom 
is seeing these T/R diode failures even when there are no thunderstorms 
then I think they should do something to better protect them.

BTW, I used a IC-746 (non PRO) for years and years and never had a 
problem. I am now using the IC-746 as my back up rig while the 756 is at 
Icom with no problems.

_______________________________________________________
Alan Zack
Amateur Radio Station K7ACZ
Official USCG Auxiliary Comm Station
Las Vegas, Nevada, USA
Delta Rocket Quality Engineer, The Boeing Company, Retired
Aviation Chief Warrant Officer,  U.S. Coast Guard, Retired
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----- Original Message ----- 
From: <k0bx at arrl.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Tuesday, March 24, 2009 12:40 PM
Subject: [ICOM] IC-756PROIII No Transmit

>
> Larry, thank you for your comments.  I do agree with what you said.
>
> But in my case, I do not have any other antenna connected.  The 1st 
> time was on 20 CW using my Hygain 204BA 4 element monobander with no 
> amp.  I agree that some RF must be getting back to the rig somehow, 
> but I do have grounding devices on all my antennas.
>
> The 2nd time, I just (Like the other guy) just turned on the rig to 
> find it dead on transmit.  I know that sounds like an e-bay thing, "It 
> worked the last time I used it".
>
> One of the gentlemen in my DX Club got rig of his PROIII after 3 
> repairs for the samething.
>
> I have used a TS-850S on this antenna for 12 years and when taken out 
> of service it performed on transmit like the day it was brought.  My 
> IC-706MK2G have been on this antenna for the last 5 years.  No 
> problems with them.
>
> As far as the Burghardt BEV-756, Burghardt recommended it as a 
> solution to my problem even though I do not use a Bev Antenna.
>
> It seems that others are having the same problem and only using one 
> antenna at a time.
>
> Joe K0BX
>
>
> Stop the insanity!
> Please do not add me to any distribution lists (Joke, Stories or Junk) 
> without my permission.
>
>
> --- On Tue, 3/24/09, Lawrence Young <k4lxv at bellsouth.net> wrote:
>
>> From: Lawrence Young <k4lxv at bellsouth.net>
>> Subject: Re: [ICOM] IC-756PROIII No Transmit
>> To: "ICOM Reflector" <icom at mailman.qth.net>
>> Date: Tuesday, March 24, 2009, 9:03 AM
>> Guys: Products like the Burghardt BEV-756 are designed to
>> serve as a front end saver for those hams who may not
>> understand that one cannot safely transmit on one antenna
>> and leave another one such as a Beverage receive antenna
>> still connected to the receiver. I am amazed at the number
>> of hams that I know who may do this without realizing the
>> possibility of damage to the radio.
>> Larry K4LXV
>>
>
> ----
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