[ICOM] Icom 7800 Problem ?

[we1x at comcast.net]

Adam,

Any insight as to what may be causing the finals to fail?

Harry

-------------- Original message -------------- 
From: Adam Farson <farson at shaw.ca> 

> Hi Larry, 
> 
> The IC-781 PSU is also switch-mode. In fact, it incorporates a shunt 
> regulator which causes a severe heat problem. 
> 
> The PSU was designed for the Japanese 100V mains supply. When fed from 120V 
> mains, the shunt-regulator dissipation increases by a whopping 44%! Over a 
> period of several years, this causes heat damage to the PSU regulator unit. 
> One way around this is to buck the mains voltage down to 110V by means of a 
> step-down transformer or Variac. 
> 
> I had an IC-781 from 1993 to 1998. The IC-756/IC-756Pro series replaced it. 
> Never looked back since. 
> 
> Cheers for now, 73, 
> Adam VA7OJ/AB4OJ 
> 
> -----Original Message----- 
> From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On 
> Behalf Of Lawrence Young 
> Sent: Wednesday, May 02, 2007 18:56 
> To: icom at mailman.qth.net 
> Subject: Re: [ICOM] Icom 7800 Problem ? 
> 
> Phil; Sorry to hear of your 7800 problems. As a retired RF and reliability 
> engineer,I would say, the only way to know the cause of your failures would 
> be to have the failed parts returned to their manufacturer for a failure 
> analysis. Anything else would be speculation. Regarding the difference 
> between the 781 having an analog supply and the 7800 having a switching 
> supply. In a well designed supply there should be no difference regarding 
> the supply loads. Good luck, Larry K4LXV. 
> 
> 
> 
> 
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