[Icom] Re:R9000 RECIVER TT-340

[George, W5YR]

Now you got me nit-picking!

If the line voltage is increased from 100 volts to 120 volts that is an
increase of 1.2. The power associated with a 1.2 voltage increase is the
square of the factor or 1.44 assuming that the load current increases
proportionally, i.e., the load remains a constant resistance, as it were.

Would this not translate into a 44% increase in heat dissipation as well as
supplied power to the rig?

What in the 781 power circuitry acts to limit the power/dissipation
increase to only 20%, the same factor as the voltage increase?

Enquiring minds want to know . . .   <:}

Seriously, I have a good friend with a mint 781 who might want to use an
autotransformer to drop the line voltage down to 100 volts. My line voltage
here is an almost constant 123 volts.

Is the over-voltage a serious enough problem to warrant dropping the supply
voltage?

On the TT front, wouldn't it be something if Icom got their new radio to
market before the dust settles on the Orion and TT finally have a reliable
working unit available in quantity?

73/72, George    
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121


Adam Farson wrote:
> 
> Johnny, Dick,
> 
> Yes indeed - the IC-781 and the R-9000 both suffered from heat problems. The
> power-supply heat problem in the IC-781 is a matter of concern. 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
> 
> Cooling-fan kits are available for both radios. On the Icom FAQ site
> http://www.qsl.net/icom/ click "IC-781 & IC-R9000 Cooling Kits".
> 
> "We have learned" that Icom is developing a high-end DSP-based HF
> transceiver to replace the IC-781 and IC-775. This radio will incorporate
> technology licensed  from Rohde & Schwarz of Munich. The projected price of
> the new radio will be in the $5K ~ $6K range.