[ICOM] RE:IC-756 PROII 6-Meter Oscillation Problem

[Frank A. Ellis]

Hi Bill,

Thanks for the link to the website . . . I had run
across it last night on a Google search, but did not
get a chance to get into the details in depth as it
was late.

To make a long story short . . . I installed an Omron
G6Y-1 PCB RF relay in my PROII and wired it to provide
a Rx path crowbar like the mod on the site and it
works very well. The one schematic on the website
shows the relay normally closed, which is in error,
you want to use a set of NO contacts that close on TX.

I did some testing on the fix and found it to be more
than adequate. My only initial concern was in CW mode
using full break-in, that the added relay would not
change state back to receive fast enough to permit
QSK, but it works just fine running a 30 wpm dit
string on Tx. After a bit of thought, I realized that
the relay does not need to fully change state to
enable the Rx path . . . all it has to do is open. So
there should be no problems at higher CW speeds using
QSK.

I want to say thanks to all who replied to my post,
there were some very helpful and informative comments.
I hope to be able to return the favor some day!

73 to all,

Frank W3UHF

P.S. I took pictures during the relay installation, if
anyone would like to refer to them prior to attempting
the mod.


--- "William J. Wickstrom"
<surgesound at wideopenwest.com> wrote:

> Frank:
> 
> My 'ProII developed the problem several years ago
> (about a year after I
> bought it new at AES), just out of warranty. At that
> time, I posted the
> description of the problem here, and the silence was
> deafening. It wasn't
> until a year or two later that by chance another
> post describing the same
> symptoms showed up here. Somebody here (I can't
> recall who) posted a link to
> a Romanian (?) website that had a fairly detailed
> description of the cause
> and a cure for this malady. The translation to
> English ain't that great, but
> you'll understand what to do. There are several very
> good images to guide
> you through. I have performed this rather simple
> modification and have not
> been able to detect any adverse effects. It is
> easily reversible, and the
> part (one SPST reed relay) was about $1.50.
> 
> Try this link:
>
http://ham.dmz.ro/icom/ic-756pro-oscillation-problem.php
> 
> Let us all know how it goes.
> 
> 73
> 
> William J. (Jim) Wickstrom, W1IK/NNN0AHC
> Technical Director, Past President
> Utica/Shelby Emergency Communication Association
> (USECA)
> w1ik at arrl.net
> www.useca.net
> 
> 
> -----Original Message-----
> 
>  Date: Mon, 15 Jan 2007 18:05:33 -0800 (PST)
> From: "Frank A. Ellis" <w3uhf at yahoo.com>
> Subject: [ICOM] IC-756 PROII 6-Meter Oscillation
> Problem
> To: ICOM List <icom at mailman.qth.net>
> Message-ID:
> <133637.33515.qm at web55510.mail.re4.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
> 
> Hi All,
> 
> My 756 PROII has developed the dreaded 6-meter
> oscillation problem. Checked ICOM America's
> Knowledge
> Base and found no matches (??!!) so was wondering if
> anyone here had any experience with the
> effectiveness
> of ICOM's fix (I believe they add an isolation diode
> in the RF feedback path, from what I have read) and
> how expensive it is to perform.
> 
> Thanks,
> 
> 73, Frank W3UHF
> 
> 
> 
>
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> 



 
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