[ICOM] IC-756PROIII No Transmit

Thu Jul 16 18:51:56 EDT 2009

About my first year at Icom Washington State University Amateur Radio 
Club had similar problems with an IC-751A and some other rigs.
They had experienced a dust storm, the static in one of those is as bad 
as a thunderstorm. Also a good snow storm can cause the same thing.
You might try seeing what happens in a darkened room sometime by 
touching the center conductor of the coax to the station ground.
I have also heard of lightning traveling up the station ground into the 
rigs. I had a few of those reports. Once I had a report of lightning 
coming out of a wall outlet, striking another wall outlet, the problem 
was the guy's rig was sitting in front of the outlet in a box. The box 
got burned and rig damaged by the lightning strike.

I would investigate your grounding. In a dry area its very hard to get a 
good earth connection. You may want to look at more ground rods 
connected together or establishing a UFER ground. Check you local rules 
about grounding in Bellevue, WA they don't want ground rods close due to 
currents around the ground rods may impede the ground.
I'll have to check my notes if I still have them I think the ground rods 
were to be 16 feet apart in Bellevue, WA for power grounds.

I suspect you need to look some more at lightning protection. MAKE sure 
there are no sharp bends in your ground wires. I never install a pretty 
neatly bundled ground wire. Think of pouring water down the ground wire 
and install accordingly straight to ground as possible. You may also 
need to do some bonding work on tower legs, and other items in your 
ground system. Any resistance will create a difference of potential and 
cause you troubles.

I spent 6 years 1980 to 1986 on the N&S railway and had lots of 
lightning issues. One hot box detector we installed 16 ground rods in 
Ohio before we solved the lightning issue. We also used #6 copper to 
connect the ground rods together. Once I straightened out the ground 
wires, made sure everything was bonded you could almost remove the 
ground wire. If hit by lightning everything would raise to that 
potential and have no damage. However if there was a potential 
difference I was in trouble. But my fixes worked for me. I was lucky I 
had good grounding. In Illinois we had to install a ground rod inside 
plastic pipe to get past some corrosive elements in the dirt. Seems to 
me we went some 15 feet down. Ground rods would corrode off in about a 
year some 3 or 4 feet down.
We used a ground rod with threaded couplers to accomplish that distance.
http://www.lightningprotectioncor.com/ was the company we used on the 
railway.  Another thing you might want to make a big loop just before 
the coax enters the shack and make sure there is some sort of drain 
installed before that loop. The loop presents impedance to the lightning 
and it wants an easier path to ground. I did this on a few repeaters 
both amateur and commercial using RG-214. Saw a few hits and always the 
hard line was spared. not sure if I was lucky or the loop did the trick. 
We also did loops for power entry on the railroad as out pole line was 
usually some 80 miles in length.

Hopefully some of this helps or stirs some thoughts about your problem.

Gary K8IZ

Alan Zack wrote:
> 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
> ---------------------------------------------------------------------
>
> ----- 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
>>>
>>>       
>> ----
>> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
>> Icom Users Net: Sundays, 1700Z, 14.316 MHz
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>>
>>     
>
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> To support QSL/QTH.net: http://www.qsl.net/donate.html
>
>   