[Icom] IC-751 FM Unit Schematic wanted

Fri, 25 Jan 2002 05:39:32 -0500

My ICOM 751 (not A) Maintenance manual, contains the following information
regarding FM operation:

Page 3-14 contains FM OPERATION.  Pages 4-2 and 4-4 contain the theory of
operation of the FM UNIT, Page 5-1, BLOCK DIAGRAM, shows a FM UNIT. On
page 5-2 there is a block diagram of a FM UNIT. The blocks identify the
ICs used.

Page 10-13, UNIT WIRING DIAGRAMS (1), shows a box outlined in dashes
rather than sold lines labeled "OPTION FM". It connects to the MAIN box.
This indicates to me it was intended to be an optional add-on board.
However, Section 7 of the manual, OPTION INSTALLATION, makes no reference
to it.  Perhaps they decided to incorporate it in all 751s but failed to
change the dashed lines to solid.

I too have found no circuit diagram. There are circuit diagrams of most
other units. Maybe that circuit is buried somewhere in this large book.

I haven't opened up my 751 to look for a board because it is on-ine 24/7
running a BBS. But, the FM mode appears to work.

Ed WC4TT

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Thursday, January 24, 2002 11:39 PM
Subject: Re: [Icom] IC-751 FM Unit Schematic wanted

> I don't think there is a separate board for FM for the IC-751.
> The radio comes equipped to receive FM (at least mine did
> when I bought it new).  I don't have a service manual for the IC-751,
> but I did get a manual for the IC-751A.  It shows the FM detector as
> an integral part of the radio, not like the IC-720 and some others
> where FM required an outboard plug-in board.
>
> If you look at Illustration 2-5 which is the Main Unit, you se the FM
> modulator circuit right in center left section right about the CW, RTTY
> oscillator section.  I don't think this is a separate board.
>
> On the right side, you see the FM IF, FM Detector circuit.  Again,
> it is an integrated part of the Main Unit and not a separate outboard
> item.
>
> Or perhaps I misunderstood your question.
>
> I hope this is helpful.
>
> Micheal Salem N5MS
>
>
>
>
> On Fri, 25 Jan 2002 00:23:58 -0000 "Michael P. Olbrisch"
> <[email protected]> writes:
> >
> >
> > > -----Original Message-----
> > > From: [email protected]
> > [mailto:[email protected]]On
> > > Behalf Of Stuart Rumley
> > > Sent: Thursday, January 24, 2002 3:11 PM
> > > To: [email protected]
> > > Subject: Re: [Icom] IC-751 FM Unit Schematic wanted
> > >
> > >
> > > Michael-
> > >
> > > Thanks for the offer to help.  I don't know what the model of
> > > the FM Unit is, its just a small internal board on the main deck.
> >
> > > I've looked through the service manual I have an cannot find
> > > any reference to the board part number or model number.
> > > What do you have?
> > >
> > > Stuart
> >
> > What I have is two units.  I have an IC-740 with the FM unit, and
> > I also have an IC-551D with an FM unit.  Both are back-up radios,
> > and they are stored away in a place difficult to get to.  If you can
> > tell me the unit number, like EX-306 of whatever, I can look it up
> > and see if that is what I have.  Dunno, you may also have the one
> > that goes in the IC-725.  I don't believe the 751 used the unit
> > for the IC-551, but it might be the one for the IC-740.  Let me
> > know.
> >
> > Mike.
> > ----
> > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > List Archives : http://mailman.qth.net/pipermail/icom/
> > List Control  : http://mailman.qth.net/mailman/listinfo/icom/
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today!  For your FREE software, visit:
> http://dl.www.juno.com/get/web/.
> ----
> Your Moderator: Dick Flanagan W6OLD, [email protected]
> List Archives : http://mailman.qth.net/pipermail/icom/
> List Control  : http://mailman.qth.net/mailman/listinfo/icom/
>