[ICOM] RE: 756Pro R8V rail

Sat Sep 23 07:24:28 EDT 2006

Adam:

Has this issue been addressed by Icom in the 'ProII, or should this fix be
applied in the 'II also?

Jim, W1IK

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net]On
Behalf Of icom-request at mailman.qth.net
Sent: Saturday, September 23, 2006 4:02 AM
To: icom at mailman.qth.net
Subject: Icom Digest, Vol 3, Issue 379

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Today's Topics:

   1. For Sale: Icom 746 (we1x at comcast.net)
   2. IC-756PRO (ve4xt at mts.net)
   3. Re: IC-756PRO (gfiber at comcast.net)
   4. Re: IC-756PRO (Tom Norris)
   5. Re: IC-756PRO (Kelly Taylor)
   6. RE: IC-756PRO (Adam Farson)

----------------------------------------------------------------------

Message: 1
Date: Fri, 22 Sep 2006 09:56:37 +0000
From: we1x at comcast.net
Subject: [ICOM] For Sale: Icom 746
To: icom at mailman.qth.net (Icom)
Message-ID:

<092220060956.3060.4513B35500019FBD00000BF4220702455398CE0A99 at comcast.net>

Content-Type: text/plain

Have for sale an excellent Icom 746 (non-Pro) with FL-222, FL-223, and
FL:232 installed. Serial number 5986.  Box, manual, DC cord, mic. $900 plus
shipping and insurance.  Reason for selling: with a 775dsp and Pro II in the
shack something has to go.

Thanks,

Harry WE1X

------------------------------

Message: 2
Date: Fri, 22 Sep 2006 14:26:21 -0500
From: <ve4xt at mts.net>
Subject: [ICOM] IC-756PRO
To: <icom at mailman.qth.net>
Message-ID: <54h9b0$3a371j at wnpgmb02-c600c.mts.net>
Content-Type: text/plain; charset=ISO-8859-1

Hi all,

I have an IC-756PRO (not II not III, just PRO) with what appears to be a
systemic issue: when the noise blanker is engaged in CW, strong nearby
signals thump the passband.

It's as though the AGC was pumping in response. Is this something
others have noticed?

Turning the NB off appears to cure the problem, but until I noticed that, I
was starting to have reservations about this radio for CW.

Thoughts?

73, kelly
ve4xt

------------------------------

Message: 3
Date: Fri, 22 Sep 2006 19:38:39 +0000
From: gfiber at comcast.net
Subject: Re: [ICOM] IC-756PRO
To: ICOM Reflector <icom at mailman.qth.net>
Message-ID:

<092220061938.25845.45143BBF0001B4FF000064F522070245539D0A0D070009 at comcast.n
et>

I suspect its the noise blanker clipping the signals causing a more of a
square wave. Square waves are richer in harmonic energies and will cause
symptoms like you describe. Probably the same thing happens on a strong
nearby SSB signal. Actually it seems to be a fairly common issue with some
noise blanker designs.

Others here may have better explainiations and cures as I don't own a
756PROII
Just have an IC-718.

Gary K8IZ
 -------------- Original message ----------------------
From: <ve4xt at mts.net>
> Hi all,
>
> I have an IC-756PRO (not II not III, just PRO) with what appears to be a
> systemic issue: when the noise blanker is engaged in CW, strong nearby
> signals thump the passband.
>
> It's as though the AGC was pumping in response. Is this something
> others have noticed?
>
> Turning the NB off appears to cure the problem, but until I noticed that,
I
> was starting to have reservations about this radio for CW.
>
> Thoughts?
>
> 73, kelly
> ve4xt
> ----
> 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/

------------------------------

Message: 4
Date: Fri, 22 Sep 2006 20:35:40 -0500
From: Tom Norris <r390a at bellsouth.net>
Subject: Re: [ICOM] IC-756PRO
To: ICOM Reflector <icom at mailman.qth.net>
Message-ID: <A4DF8ECF-8848-4DC8-ABCE-4605E03E4289 at bellsouth.net>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

There is a fix for that, I had to do that to my Pro.  It was gone
over in QST back in June 2002, It is in detail on mods.dk.  Basically
it involves adding a capacitor.  This will cure the "click click"
from adjacent strong adjacent CW signals and the ghostlike rumbling
that might be heard from nearby strong SSB signals.

Tom NU4G

On Sep 22, 2006, at 2:26 PM, <ve4xt at mts.net> <ve4xt at mts.net> wrote:

> Hi all,
>
> I have an IC-756PRO (not II not III, just PRO) with what appears to
> be a
> systemic issue: when the noise blanker is engaged in CW, strong nearby
> signals thump the passband.
>
> It's as though the AGC was pumping in response. Is this something
> others have noticed?
>
> Turning the NB off appears to cure the problem, but until I noticed
> that, I
> was starting to have reservations about this radio for CW.
>
> Thoughts?
>
> 73, kelly
> ve4xt
> ----
> 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/

------------------------------

Message: 5
Date: Fri, 22 Sep 2006 20:58:37 -0500
From: "Kelly Taylor" <ve4xt at mts.net>
Subject: Re: [ICOM] IC-756PRO
To: "ICOM Reflector" <icom at mailman.qth.net>
Message-ID: <001c01c6deb3$c8ef5c40$6c02a8c0 at user64b8a9c0be>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
        reply-type=original

Hi Gary,
Apparently, it's due to insufficient bypassing on the 8volt buss. An
additional capacitor is said to be the cure.

73, kelly
ve4xt
----- Original Message -----
From: <gfiber at comcast.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Friday, September 22, 2006 2:38 PM
Subject: Re: [ICOM] IC-756PRO

>I suspect its the noise blanker clipping the signals causing a more of a
>square wave. Square waves are richer in harmonic energies and will cause
>symptoms like you describe. Probably the same thing happens on a strong
>nearby SSB signal. Actually it seems to be a fairly common issue with some
>noise blanker designs.
>
> Others here may have better explainiations and cures as I don't own a
> 756PROII
> Just have an IC-718.
>
> Gary K8IZ
> -------------- Original message ----------------------
> From: <ve4xt at mts.net>
>> Hi all,
>>
>> I have an IC-756PRO (not II not III, just PRO) with what appears to be a
>> systemic issue: when the noise blanker is engaged in CW, strong nearby
>> signals thump the passband.
>>
>> It's as though the AGC was pumping in response. Is this something
>> others have noticed?
>>
>> Turning the NB off appears to cure the problem, but until I noticed that,
>> I
>> was starting to have reservations about this radio for CW.
>>
>> Thoughts?
>>
>> 73, kelly
>> ve4xt
>> ----
>> 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/
>
>
> ----
> 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/
>

------------------------------

Message: 6
Date: Sat, 23 Sep 2006 00:21:01 -0700
From: Adam Farson <farson at shaw.ca>
Subject: RE: [ICOM] IC-756PRO
To: 'ICOM Reflector' <icom at mailman.qth.net>
Message-ID: <004d01c6dee0$d4058550$0300005a at max>
Content-Type: text/plain; charset=us-ascii

Hi Kelly,

There is an issue in the 756Pro which causes the noise blanker to impress a
low-frequency ripple on the R8V rail feeding the receiver audio chain. Here
is the fix:

http://www.ab4oj.com/icom/756pro_nb/main.html

Cheers for now, 73,
Adam VA7OJ/AB4OJ

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of ve4xt at mts.net
Sent: 22 September 2006 12:26
To: icom at mailman.qth.net
Subject: [ICOM] IC-756PRO

Hi all,

I have an IC-756PRO (not II not III, just PRO) with what appears to be a
systemic issue: when the noise blanker is engaged in CW, strong nearby
signals thump the passband.

It's as though the AGC was pumping in response. Is this something others
have noticed?

Turning the NB off appears to cure the problem, but until I noticed that, I
was starting to have reservations about this radio for CW.

Thoughts?

73, kelly
ve4xt

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------------------------------

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