copied from the Internet:
From: cromwell@rvl2.ecn.purdue.edu (Bob Cromwell)
Newsgroups: rec.radio.amateur.misc
Subject: ICOM IC-229H, and AM aviation band modification

Eons ago, I asked:

> Does anyone know what is required to make an Icom IC-229A (or IC-229H)
> receive in the aviation band (118-136 MHz or so)?

More detailed:

  --  To disassemble the radio,
(a)	When removing the top and bottom case halves, be careful, as
        the speaker is connected to one!
(b)	Remove the three knobs by gently pulling them straight out
        from the panel.
(c)	With a spanner (or needle-nose pliers) remove the nut mounting
        the front panel to the microphone connector.
(d)	Now remove the screws holding the front panel (black plastic)
        to the frame, and remove that panel.
(e)	You will now find that there is a subassembly with a
        "backbone" of 0.25" machined plexiglass, held to the frame
        with three machine screws.  Remove those screws and gently
        swing that subassembly away from the frame.  You now have
        access to the diode that must be clipped.  D5


	Oh yeah, when you rotate the knob in "VFO" mode to tune up from
174 MHz, it skips to the range 340-380, and then to 870-890, before wrapping
around to 118 again.  Don't get excited, it doesn't receive in 340-380 or
870-890, as the VCO won't lock up there.  It does AM demod 118-134 and
FM 134-174 MHz.

	On to the excerpts....  For the following, only the pad pair marked
as "D5" had a diode in my dad's:

> 
> I retrieved this from my "archive"  -- hope it helps!
> --James N5KNX
> 
> Here's some info on the IC229A/H, 
> 
> The stock radio has RX: 136 - 174, TX: 140-150, FM only.
> 
> When diode D5 (conventional, upright diode on the logic board)
> is cut, 118 - 135.995 MHz can be received in AM mode.
> [Local reports indicate the audio is acceptable but not as good as,
> for example, AM received on a PRO-2004 scanner]
> 
> To expand TX to 136 - 174 MHz, locate chip diode D9.  Ascertain that
> the vertical pair of pads to the right are OPEN.  Short the next pair
> of vertical pads to the right [with solder, perhaps].
> 
> These changes pertain only to the USA model.
> 
> Here's some ASCII art to clearify:
> _________________________________________________________
>   R5   R4                                               !
>               R1                                        !
>             R2 .    .
>               D1   D2
> -----------+  ..   ..
>            !   -D3-
>            !   -D4-
>    IC4     !   -D5-
> -----------+   -D6-
>                -D7-    .   ..  _  _
>                       D8   D9  _  _
>                 O     ..    .
>                C7
>     X1                                                  !
> ________________________________________________________!

Note: I haven't tried or verified this, proceed at your oun risk.  And
do not transmit outside of legal bands!  WA2ISE
/EX