[ICOM] OPC-581 data.

[Mike Olbrisch]

I have been building a Pedestrian Mobile system using an ICOM IC-703 plus as
the radio.  What makes this radio so perfect is the ability to remote the
control head to your chest while mounting the bulk of the radio in the back
of the frame with the battery and antenna.  The problem though, is what to
do with all the excess remote cable?  I have been considering cutting a
cable, but I have been reluctant to just destroy a perfectly good cable.

Thanks to Ernest - AA1IK, I received a broken OPC-581 to play with.  Today
was a very quiet day on the transmission and generation desk at work despite
the 100ºF + heat, so I used my lunch break to disassemble the cable and see
what was up.

Ernest, the cable was in fact bad.  It had a short in the mic-audio line.
SSB transmit had no output because the mic audio was shorted.  I really
hoped it was only a dirty contact.  RATS!!!

With nothing to lose now, I started by cutting the cable in half, to
determine which half was shorted.  It was the control-head end.  So I
started with the radio end and mapped out the wires and pins.

Cutting into the wire, I discovered there were 9 wires in it, but only 8
pins on the ends.  I stripped back the outer rubber cover, it is quite
thick.  Even so, use a very sharp blade and cut carefully.

Under the rubber is a single wire and a foil wrap around the rest of the
wires.  This single wire has no connection at either end.

After removing the foil, there was a further white fiber covering the wires.
It looked like tissue paper, only much stronger.  This too was removed.
This exposed the wires.

There are two shielded wires in the cable.  One has a bare copper shield
with a red conductor inside.  The other has a green-enameled shield with a
white conductor inside.

Looking at the plug end for the radio side, viewing the pins, it is
rectangular, and has one end open.  With the opening to the bottom, the pins
are numbered so.  (I hope the formatting holds).

------------------
|* * * * * * * * |

 1-2-3-4-5-6-7-8

Pin.     Color.
1        Yellow
2        Black
3        Blue
4        Red (in copper shield)
5        Copper Shield
6        White (in green shield)
7        Green Shield
8        White

Next, I started in on the control head side.  Looking at the plug end for
the control head side, viewing the pins, it is rectangular, and has two
square notches on the bottom.  

 ------------------
 |* * * * * * * * |
   |___________|

  1-2-3-4-5-6-7-8

Pin.     Color.
1        White
2        Green Shield
3        White (in green shield)
4        Copper Shield
5        Red (in copper shield)
6        Blue
7        Black
8        Yellow

The Green shield/white wire are the mic audio, and were shorted.  In an
effort to see if I could resurrect this cable, I cut a foot off and measured
it.  Still shorted.  Cut another foot.  Still shorted.  Cut another foot.
Still shorted.  Finally I go to the point where I actually removed the
molded strain relief and cut into the plug to expose the wires.  Still
shorted!  RATS!  Alas - not repairable at my level of maintenance.

I hope this data helps someone else interested in shortening their cable.

ALSO - IF ANYONE HAS A BROKEN CABLE that I might use in cunjunction with the
half that I have, please think of me.  Or at this point a cheap deal on a
good cable would work too.

Good luck and thanks.

Vy73 - Mike - KD9KC.
El Paso, Texas - DM61rt.
W5-SOTA Association Manager.
NA-SOTA info: http://na-sota.org/





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