[ICOM] IC746 Backlight Failure

[Larry Gauthier (K8UT)]

Mike,

Display tube driver transistor failure is a known problem on early 746's --  
in fact the Icom repair folks at MTS replace them with slightly beefier 
transistors. My 746 failed several years ago and I repaired it myself - here 
is my summary at the time:

> For those who inquired, here's the text of my exchange with Scott from MTS
> (a company that repairs Icom gear - and very helpful guys, I might add!)
> regarding display driver failures on the IC-746.
>
> Performing the repair in not difficult, but I would not recommend it to
> those without some soldering/desoldering experience. The repair involves
> disemboweling the rig to get the S-logic board out; removing a metal 
> shield
> that covers the transistors (about six solder connections); and then
> removing/replacing the surface mount transistor. The part itself is 
> cheap - around $3.00.
>
> In a previous life, I was a ham tech and solder-slinger at Heath, so I
> attempted the repair and was not too concerned about the soldering part. I
> was far more concerned about losing my rig for a couple of weeks having
> someone else fix it (plus the cost of the repair itself, of course).
>
> I hope this helps,
>
> -larry
> K8UT
>
> ==========================================================
>> Hi Larry:
>> >
>> > Yup, we have seen this problem a couple of times.  It is the pass
>> > transistor for the DC/DC converter for the back lighting tube.  We are
>> > using a upgraded transistor, 2SB1202, and so far they seem to be 
>> > holding
>> > up allot better, no repeats.  It is Q302 on the S-logic unit.
>> >
>> > For us to do the repair, we have been running about $60 plus shipping.
>> >
>> > Thank you for contacting us, and if you have any questions, please let
>> > me know.
>> >
>> > Scott Malcom
>> > MTS
>> >
>> > M T S
>> > 3617 Deep Lake Bdry Rd.
>> > Colville,  WA  99114-9142
>> >
>> > 509 732 8883
----- Original Message ----- 
From: "Mike" <k4gmh at arrl.net>
To: <icom at mailman.qth.net>
Sent: Monday, May 30, 2005 20:03
Subject: [ICOM] IC746 Backlight Failure


> Hello,
>
> The display's backlight on my IC746 has gone out.  The LCD adjustment was 
> at 50% and adjusting it to 100% didn't help.  About a month ago the 
> backlight went out, but returned after the radio was cycled on/off.  This 
> time the cycling didn't work.
>
> I do have the service manual, but would like to have a good idea on what 
> to look for before digging into the radio.  Also, having the replacement 
> on hand would be nice so the radio could be quickly put back together and 
> back on the air ASAP.
>
>         73,
>         Mike, K4GMH
>
> ----
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