[Icom] Heat in the IC-781 and others.

Wed, 6 Feb 2002 18:05:32 -0500

Mike,

Sherwood Engineering has a cooling kit for the R9000. I do not know if it
would work for the 781 but it might be worth asking.

http://www.sherweng.com/

73, Hal -K4HW

----- Original Message -----
From: "Adam Farson" <[email protected]>
To: <[email protected]>
Sent: Wednesday, February 06, 2002 2:05 PM
Subject: RE: [Icom] Heat in the IC-781 and others.

> Mike,
>
> As you are doubtless aware, the power-supply heat problem in the IC-781 is
> quite serious. The power supply uses a shunt regulator, and was designed
for
> the Japanese 100V mains supply. When connected to 120V mains, the power
> supply dissipation increases by 20%. The heatsink was not designed for the
> additional thermal load; consequently, the power-supply area runs very
hot.
> This can lead to component breakdown over time. Further reading:
> http://www.icomamerica.com/support/troubleshooting/ic-781.html
>
> The CRT module is another heat source. Over time, several resistors on the
> CRT board can overheat and char the board.
>
> When I had an IC-781 in my shack, I helped it "keep its cool" by setting
up
> a 20cm diam. table fan to blow a high volume of air across the heatsink at
> the rear of the radio. To reduce heat generation, you could combine the
> external fan with a 100V mains supply to the radio (derived from a 2.5 kVA
> bucking transformer, obtainable at any electrical supply house). The
bucking
> transformer should be configured to buck the 120V mains by 20V.
>
> Best 73,
> Adam, VA7OJ/AB4OJ
> North Vancouver, BC, Canada
> http://www.qsl.net/ab4oj/
> Note new e-mail address:
> mailto:[email protected]
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Michael P. Olbrisch
> Sent: Wednesday, February 06, 2002 08:36
> To: _ICOM_list (E-mail)
> Subject: [Icom] Heat in the IC-781 and others.
>
>
> Howdy fellow Icom-ers,
>
> I will be pulling my IC-781 out of the operating position
> in a few days to give it its annual cleaning, and to replace the
> old battery.  I know the 781 runs hot, I have had a fan blowing
> on the heat sink for years now.  But this will be a perfect time
> to look at improving on it if I can.  In the past, I have heard
> several suggestions here on the list, but I do not remember them.
> If you have a 781, or another like it, how have you fixed the
> heat problem?
>
> Mike.  KD9KC
>
>
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