[ICOM] IC-756ProII Display, Receive dead

Thu Oct 23 00:20:53 EDT 2014

Jim; Sorry to hear of your ProII failure. From your description, It would appear that a problem has occurred in one of the radios supply voltages. As I no longer have either of my previous Pro series radios I do not have documentation for them. I remember there is a 5 amp fuse in the radio. I suggest you check it and find and measure the various DC supply voltage rails such as the +8 V, and +5 Volt  supply lines among others. Barring this, you may wish to utilize one of the excellent repair facilities such as W6XA in SC or Icom Michigan. The problem sounds simple to correct.

Larry K4LXV

On Wednesday, October 22, 2014 1:20 PM, Deric Affleck <deric.vy2da at bellaliant.net> wrote:

Hello Jim,

Last January/2014 I had the display of my IC-756 Pro III go dark when I 
turned it
on one morning - it was fine when I had turned it off the previous night.
Unlike your symptoms the receiver and transmitter worked fine - just no 
display
making it impossible to operate the radio properly. Fortunately my Pro III 
was
interfaced with my laptop so I could use Ham Radio Deluxe to manipulate the
various functions. This occurred right in the middle of the FT5ZM DXpedition
to Amsterdam Island so I was still able to contact them even without the 
display.
I scoured the internet looking for possible solutions and came across the 
following
links on You Tube concerning various problems with the older IC-756 
including display
failure and symptoms similiar to your Pro II so take a look at these videos 
showing
what is involved in locating and repairing similiar symptoms to yours of 
course discounting
the upgrading the display in the old Pro transceivier. Even though the 
actual circuit board
layout may differ between the Pro and the Pro II the circuit should be quite 
similiar.

http://www.youtube.com/watch?v=aMTMAZSEhOw

http://www.youtube.com/watch?v=Q3POkGIA6rk

In my Pro III the fault was a failed inductor in the power supply circuit 
for the backlighting circuit
for the display. The inductor opened shutting off the supply voltage for the 
backlight.
By watching the above video links I learned how to take remove the display 
circuit board
from the front panel, locate and replace the faulty inductor. I used a 
slightly larger J.W. Miller
inductor with better current rating that the Icom part so it won't act like 
a fuse again. By the way,
I contacted Icom USA who claimed they never encountered this problem before 
(deny, deny, deny)
and since the Pro III is an obsolete radio they don't stock the parts and 
even though I gave them
the Icom part # they said they didn't have it. It obviously is a common part 
to other Icom radios but
I was told they couldn't cross-reference it. Anyhow I purchased several new 
inductors from an eBayer
to have some spares which I probably will never need now. It took more time 
to dis-assemble the radio
than to replace the inductor, which by the way, was the only non-SMD part in 
the backlight power supply
and was a normal solder thru the board type. After re-assemblying my Pro III 
I turned it on with bated
breath - the display came to life and has been working normally for the past 
9 months - touch wood!
Unfortunately, I think your problem is more involved than mine was so take a 
look at the video links to
give you an idea what could be the cause.

Good luck & 73,

Deric, VY2DA
-------------------------------------------------------------------------------------------------------------------------------------
> Hey, Gang:
>
> The other night I put my trusty 'Pro II to bed in my usual way (powered it
> down with the front panel power button and disconnected the antennas) 
> after
> using it on two nets with no issues. When I attempted to power it up the
> following morning, the display was totally dark (no backlight, do
> discernible characters), the S meter stood steady at around half-scale, 
> and
> there was no audio output. The S meter backlight and LED indicators were
> lit, however. I tried a "hard reset" of the CPU, to no avail. I checked 
> the
> power supply voltage at the screw terminals inside the rig, and measured
> 13.8 VDC. I visually inspected the chassis throughout, verified that all
> connectors and ribbon cables were seated, etc., but turned up nothing
> unusual.
>
> Before I pack the rig up for shipping to Icom Service, does anyone have 
> any
> suggestions as to what else I might check? I am a fairly capable (if I do
> say so myself) bench tech, and have a good compliment of basic test gear.
> What I'm really short on is TIME, so I'm hoping some of you here can offer
> some guidance as to where best to look next.
>
> Thanks!
>
> W1IK
>
> William J. (Jim) Wickstrom, W1IK
> Technical Director,
> Utica/Shelby Emergency Communication Association (USECA)
> w1ik at arrl.net
> www.usecaarc.com
>
> ----
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> 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