CQ-Contest
[Top] [All Lists]

Summary of mail on IC-775DSP Failures

Subject: Summary of mail on IC-775DSP Failures
From: jbmitch@vt.edu (John Mitchell) (John Mitchell)
Herewith, largely unedited is the e-mail received in response to my query on
the unusual IC-775DSP failures noted during recent winter storms (snow
static induced transceive failures)
----------------------------------------------------------------------------
--------------------------------------------
During a high wind snow storm in 1980 a fellow ham at my shack was sent
flying across the room after touching the center conductor of my 160 ant
pl259. The high voltage discharge could be affecting the high swr shutdown
curcuit. or back biasing the TR relay possibly. In either case the rig
is not transmitting. On any large 160 antenna I recommend a very large RF
choke to ground to bias off static buildup. This choke could be made of
a ferite rod and lots of turns. Remember it is going to explode with a
lightning strike. A vertical also needs a spark gap that will dissipate
the lightning after the choke explodes. The choke needs to have enough
reactance at 160. and you should not hear a difference in recieve when
installed. On high static days it may actually quiet recieve/rain/snow static.
Good luck and high B+        Bob k0DD
----------------------------------------------------------------------------
--------------------------------------------
I have a 775 and just wanted to let you know that not all of them are 
suffering the same problems.  We have has several bad storms here and I 
operated right through them with no problems.  It may have something to 
do with the specific installation and design of the antennas.  All of 
mine are Beta or Gamma matched and there is little chance of static 
charge building up on the center conductor, since the elements are all at 
ground potential.

Will be interested to see your summary.
BTW, I love my 775!
----------------------------------------------------------------------------
-------------------------------------------
ICOMs are delicate radios.  K4VUD

----------------------------------------------------------------------------
--------------------------------------------
Let me tell you how delicate I think Icom are:

A year or two ago, my friend was over here with a beta version of the 
Icom 736.  We were fooling around with it, just for fun, trying to see 
how it performed.  I unscrewed the coax from the back of my tuner and 
placed it on the 736 (I thought!)  We even decided to listen to the audio 
of the 736 on my IC-781.  I figured that since the antenna was 
disconnected from the tuner (which was connected to my 781), AND since I 
cranked-in 30 db of attenuation, I should be safe.  Well, the audio 
sounded good, and I headed out to McDonald's for a couple of sandwiched 
while my friend tried a few CQ's on the 736.  He noted that it hadn't 
autotuned easily on the normal mode, so he had taken off the bottom panel 
and set the tuner to "WIDE", which fixed the problem.  We figured it was 
just sensitive to my 160 meter loop.  He got full 100 watts out, and 
started on his mission as I left.

A short time later, I returned to find him standing in the driveway 
looking like a "beat dog"!  I knew something was wrong, but would  never 
have guessed the problem.

He explained in his "sickliest" voice that we had unplugged the wrong 
coax cable from the back of the tuner, and had instead plugged the 
transmit output of the 736 DIRECTLY into the receive jack of my 781!
Well, SHIT HAPPENS, and I told him to not worry about it, and I even 
found my idiocy somewhat humorous.  We went inside and checked the 781 
for performance.  Believe it or not, it worked VERY WELL indeed, and even 
surpassed the 736 on an A-B receive test.  I had already invited a bunch 
of young hams over for a fun (learning experience) SSB multi-op effort, 
so we went ahead with the contest all night.  We did as well as we 
expected to do, and the radio performed well.

That was possibly the most expensive dummy load ever used by an amateur. 
I'm only glad that my friend was getting many responses to his CQ's, 
because he may have worked dozens of 'em, shooting a hundred watts of RF 
right into the innards of Nellie Belle.

It was time for Nellie's tune-up anyway, so I boxed her up and sent her 
to Icom in Bellevue to my favorite tune-up man, Charles Rocha. (I see now 
that the repair date was 3/14/94.)  They "located and resoldered cracked 
and overheated joints on reg. unit.  Located and replaced burned 
components on RF and AT unit.  Repaired burned foil traces on RF unit.  
Replaced open pilot lamp.  Complete check-out and alignment as needed."  
From my viewpoint, my 781 took a lickin' and kept on tickin'.  This 
places it in a catagory far from "DELICATE".  I hear lots of pros and 
cons about radios, but I LOVE MINE!  It's the "Daddy". (Whoops..."Momma")!

I've had a Kenwood TS-440SAT which played good but quit bigtime in the 
middle of Field Day in '90 or '91.  I've had the 765, with which I had no 
problems, and the 781 has served me well for years.  It is a tank.

Just one man's opinions.  (Not a very smart one, at that!)

Steve Sample / AA9AX  

----------------------------------------------------------------------------
--------------------------------------------
I have an IC-775DSP which I think is a tremendous radio.  The only problems I
have had are:

1.  The tuning knob (binds up after the radio gets very hot, like after 24
hours of use).  Icom says they will fix this, has to do with the lubricant of
the optical encoder.

2. One time I had a problem such as you report.  I cleaned the screen of my
computer CRT, and then touched the radio.  Must have transferred some static
charge.  The radio went blank (could not receive anything, nor tune
anything.)  I turned the radio off and on, and the problem went away and has
not returned.  I wonder if your problem was fixed by this "reset" method ?

73, Joe N7XX
----------------------------------------------------------------------------
--------------------------------------------

Joe, the radios in question belonged to friends, and, as far as I know, all
went back to ICOM.

I've certainly learned a lesson:  use an rf choke!!  Snow static is for mi
da' ble.

73 to all

John WD4MUR


<Prev in Thread] Current Thread [Next in Thread>
  • Summary of mail on IC-775DSP Failures, John Mitchell <=