[ICOM] Re: IC781 Power Supply

[Glen Rosenthal]

That amount of heat over time, whether generated from a 120v or 100v supply 
will cause electrolytics to dry out plus cause large solder pads to crack 
much more quickly.

Ovehauling the powersupply and/or providing a solid cooling mechanism like 
the Sherwood Engineering cooling kit will increase the life of the 
components.

73,
Glen

>From: "Don\\" <k1vsk at cox.net>
>Reply-To: ICOM Reflector <icom at mailman.qth.net>
>To: "ICOM Reflector" <icom at mailman.qth.net>
>Subject: Re: [ICOM] Re: IC781 Power Supply
>Date: Fri, 4 May 2007 08:38:16 -0400
>
>Good graphics but I can't help wonder if the whole test is meaningless 
>given the highest temp of 125F can't reasonably be expected to do any 
>damage to a baby's bottom, never mind a power supply board component.
>Am I missing something?
>Don/K1VSK
>
>
>----- Original Message ----- From: "Glen Rosenthal" <n0nr at hotmail.com>
>To: <icom at mailman.qth.net>
>Sent: Thursday, May 03, 2007 9:41 PM
>Subject: Re: [ICOM] Re: IC781 Power Supply
>
>
>>
>>For your interest, here is a link that might provide additional insight 
>>regarding 120v vs. 100v supplied to the 781.
>>http://home.earthlink.net/~fsense/k8ac/781Temperatur.html
>>
>>73,
>>Glen
>>
>>
>>>From: <n6lrv at cox.net>
>>>Reply-To: ICOM Reflector <icom at mailman.qth.net>
>>>To: ICOM Reflector <icom at mailman.qth.net>
>>>Subject: Re: [ICOM] Re: IC781 Power Supply
>>>Date: Thu, 3 May 2007 9:43:57 -0700
>>>
>>>Lee,
>>>Rob Sherwood's kit is available at this link;
>>>http://www.sherweng.com/IC781Fan.htm
>>>Gary
>>>---- "Lee Mairs (SAG)" <lmairs at sagcorp.com> wrote:
>>> > Can someone point me to the Sherwood mod mentioned below?  My 781 has
>>> > been going strong for about 15 years.  I'd hate to lose it now.
>>> > 73 de Lee
>>> > KM4YY/8
>>> >
>>> >
>>> >
>>> > mel martin wrote:
>>> > >> The PSU was designed for the Japanese 100V mains supply. When fed
>>>from 120V
>>> > >>
>>> > > mains, the shunt-regulator dissipation increases by a whopping 44%!
>>> > >
>>> > > Hi Adam...
>>> > >
>>> > > A while back someone actually ran temperature tests on the 781 power
>>>supply.
>>> > > I think the data was on this reflector... At least a link to it. I
>>> > > distinctly remember that the rise in ambient temperature with a 120V
>>>mains
>>> > > supply as opposed to a 100V supply was trivial. The obvious > > 
>>>conclusion
>>>is
>>> > > that the mains supply not is not the issue... The power supply also
>>>ran far
>>> > > too hot at 100V... So all those 781s out there running on Variacs 
>>>are
>>>at
>>> > > risk. What is needed is additional cool air. I use the Sherwood
>>>Engineering
>>> > > kit... And it works very well.
>>> > >
>>> > > I wish I still had the reference. Perhaps someone can provide it.
>>> > >
>>> > > ----
>>> > > Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>>> > > Icom Users Net: Sundays, 1700Z, 14.316 MHz
>>> > > Icom FAQ: http://www.qsl.net/icom/
>>> > >
>>> > >
>>> > >
>>> > ----
>>> > Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>>> > Icom Users Net: Sundays, 1700Z, 14.316 MHz
>>> > Icom FAQ: http://www.qsl.net/icom/
>>>
>>>----
>>>Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>>>Icom Users Net: Sundays, 1700Z, 14.316 MHz
>>>Icom FAQ: http://www.qsl.net/icom/
>>
>>_________________________________________________________________
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>>----
>>Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>>Icom Users Net: Sundays, 1700Z, 14.316 MHz
>>Icom FAQ: http://www.qsl.net/icom/
>
>----
>Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>Icom Users Net: Sundays, 1700Z, 14.316 MHz
>Icom FAQ: http://www.qsl.net/icom/

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