[Icom] IC746PRO

Sun, 10 Mar 2002 15:39:35 -0500

This sort of thing is just what can't get stressed enough, Install a
grounding system for your station and bond all the RF energized components
to it at a common point, no daisy chains, keep the RF grounding away from
your AC power ground system ,and on the AC ground system bond all items
capable of becoming energized with 110vac/240 vac to these points. I have
done this for years and have yet to have a power spike or lightning
disaster. Some will argue the RF/AC ground system is contrary to the
national electrical code, no it isn't read the sections closely and you will
see. As a electrical contractor here we practice this diligently and have
yet to have lost a house or single motor to these problems. I have heard of
hams using the ground prong on their AC plugs to ground their stations, if
your one doing this you are asking for BIG PROBLEMS down the road. Call a
pro to get you grounded the right way
ken w8ob
----- Original Message -----
From: "Paul Playford" <[email protected]>
To: <[email protected]>
Sent: Saturday, March 09, 2002 1:36 AM
Subject: Re: [Icom] IC746PRO


> Yup, same transistor failed in my '765.  Several times, along with filter
> switching diodes.  Turned out to be a less than adequate connection
between
> my station ground and my tower.  Everytime I turned my antenna the Ham M
> rotator applied 2 to 3 volts a.c. to the housing of the rotator (via the
> direction indicator potentiometer wiper) at the top of the tower which fed
> back down the feed line and blew the transistor.  If you look really close
> at the IC-765 schematic you will find a sneak path for this voltage to get
> to the base of the pre-driver transistor.  I stumbled on to the cause of
> this by installing a couple of diodes in parallel across the antenna
> terminals (I was getting desperate after so many failures) to see if
> atmospheric static was destroying the transistor.  The next time I turned
> the antenna I heard the most god-awful buzz from the radio.  To prove the
> cause I just put a ground lifter on the rotator control and the buzz went
> away.  I now have a good connection between my tower and station ground
and
> no further problems.
>
> Can't help but wonder how many of these pre-driver transistors have given
> the '765 a bad reputation when the problem is caused by external faults.
>
> de Paul, W8AEF
>
> ----- Original Message -----
> From: Tony Hwang <[email protected]>
> To: <[email protected]>
> Sent: Sunday, March 10, 2002 3:16 AM
> Subject: Re: [Icom] IC746PRO
>
>
> > Hi,
> > I dare to say some of questions asked from high end radio owners make me
> > wonder. Maybe something to do with operators? No matter how well
> > equipment is made, if the operator does not know how to operate it
> > properly, then it can easily break. My old 765 had exactly same problem
> > the same x-sistor you mentioned went once and repelacing it was a cinch.
> > Just took time to warm up the soldering iron. I think QC standard of
> > operators in general as well is questionable these days. Looks like
> > everybody is becoming an AO.
> > 73,
> > Tony, VE6CGX
> >
> > "George, W5YR" wrote:
> > >
> > > Which raises the question as to why so many postings on the TT list
are
> > > concerned with user mods and fixes to correct problems that sound like
> they
> > > should never occur with properly designed equipment manufactured under
> even
> > > minimally adequate QC standards.
> > >
> > > Having to resolder joints, reroute and reseat cables, tighten mounting
> > > screws, and add shielding, ferrite beads and bypass caps to correct
> > > internal RFI problems does not strike me as evidence of QC to be
> admired.
> > > In contrast, my 11 year old Icom IC-765 has had only one part failure:
> the
> > > transmitter pre-driver transistor. And my 756PRO which has been
operated
> up
> > > to 18 hours a days for the past year and a half has yet to hiccup or
> fail
> > > to perform in every respect according to spec. And my 1982 IC-730 has
> yet
> > > to require any maintenance at all.
> > >
> > > I must be missing something here . . .
> > >
> > > 73/72/oo, George W5YR - the Yellow Rose of Texas
> > > Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
> > > Amateur Radio W5YR, in the 56th year and it just keeps getting better!
> > > QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
> > > Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437
> > >
> > > All outgoing email virus-checked by Norton Anti-Virus 2002
> > >
> > > "Caitlyn M.Martin" wrote:
> > > >
> > > > On Fri, 8 Mar 2002 23:44:16 -0500
> > > > "Steve Jones" <[email protected]> wrote:
> > > >
> > > > > Thanks for the photos, but unless Ten Tec gets their QC fixed, I
> would not
> > > > > touch a radio from there. I like my FT1000D too much, Looking at
the
> Pro II
> > > > > now, especially new for 2735.00. 73, Steve
> > > >
> > > > Hmmm... based on my experience, I'd take Ten Tec QC over Yaesu any
> day, and over Icom on most days.
> > >
> > > ----
> > > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > > Icom FAQ: http://www.qsl.net/icom/
> > ----
> > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > Icom FAQ: http://www.qsl.net/icom/
> >
>
> ----
> Your Moderator: Dick Flanagan W6OLD, [email protected]
> Icom FAQ: http://www.qsl.net/icom/
>