HOW-TO reach the front panel of IC-728
              for changing a burnt display lamp
                  by Paolo Cravero IK1ZYW
                  (ik1zyw at qsl dot net)


23/Feb/2005, update.
A fellow HAM reported that this procedure worked on his Icom IC-725.
* I have personally NOT tested the procedure on the 725, so try it
at your own risk *


8/Jul/2001.

Recently one of the three display lamps of my IC-728 burnt. I don't really
know how it could happen, since it apparently broke while moving the
transceiver to another location.

The user manual does not describe how to reach and change the lamp,
although on the schematic diagram they are clearly indicated. Therefore I
had to find the way on my own.

DISCLAIMER: if you decide to follow the following instructions I do not
consider myself responsible for any material loss and/or damage or
personal injury. Follow the procedure described at YOUR OWN RISK.

PROCEDURAL NOTE: you will remove a LOT of screws. You are strongly advised to
prepare 3-4 small boxes to keep them separated according to their original
location (upper/lower panels, front panel mounting support, ...)

1) Unplug the transceiver from all cords: mike, CW key, power line, ...

2) Follow the user manual instructions on unscrewing and removing the upper
and lower covers.

3) You do not need to remove the front plastic panel as I first though of, as
well as the heat-sink

4) Position the 728 in its natural state and locate the following screw
couples:

  * on top those keeping the front panel connected to the heatsink
  * on left side the couple keeping the front panel screwed to the
    circuit-board metallic frame (lower part of the RTX)
  * on the right side, as on the left

All these 6 screws have the same goldish metallic colour.

5) Gently lay the 728 on one side (careful not to touch any component on the
board or damage the little loudspeaker!)

6) Move apart the front panel paying attention not to break any of the
connecting wires. You won't be able to move it too far away, but it is enough
space for (un)soldering the lamp

7) Locate the lamps by looking for three identical holes on the side of the
green board that could be considered close to the top of the transceiver

8) Unsolder carefully the burnt lamp and extract it from its location

9) Remove the yellow rubber cover from the lamp and put it together with
removed screws

I couldn't locate on any paper or Web page IC-728 lamp characteristics, so I
measured at least their operating voltage. Across lamp terminals I could
measure about 12 volts (obviously after connecting the power cord and
switching the RTX on)

I have heard that ICOM's original part costs 2.5 US$. Mine was 0.4 US$.

10) Go to your favourite electronic parts store with the lamp and buy a
replacement. I have been told they are used in car-audio displays. Be
careful to buy the 12 volts one, and not 6 V!

11) Come back home, cut the terminals to the lenght of the original lamp,
put the yellow rubber on, solder it in place

12) Test if it works: plug the power cord to IC-728 and switch it on

13) If everything works, follow backwards these instructions to get your
IC-728 reassembled (from 6 to 1)

Final note. There is probably a current rating difference between the
replacement I got and the original lamps. In fact the new one is more dim
than the other two. If you want you can replace all original lamps with
new ones, and there is actually place for a 4th one on the IC-728 front
panel PC board.

Happy DXing!
Paolo Zyw


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