[Swan] Balanced Modulator R's

[dean at laptop4hire.com]

Bob -

All of the suggestions that I have ever seen written up about those
resistors says to increase them to one watt, that they run very hot at 1/2
watt and age and change value.

Regards -- Dean / WA6IKJ

On Sat, 17 Jan 2009 20:36:17 -0600, Robert Nickels <ranickel at comcast.net>
wrote:
> I recently found all the resistors between B+ and the carrier balance
> pot on my 600T had gone open circuit, and after doing the math, it looks
> like the Swan engineers just cut the power dissipation too thin.  The
> 600T uses the 6JH8 and Ohms Law says the 27Ks will be cooking right at
> 0.47 watt with the carrier balance pot centered and 215 volts of B+.
> Problem is, the B+ only drops that low under full power transmit, so 95%
> of the time the B+ will be up around 280V, increasing the dissipation
> well over 1/2 watt .  The common 10K dropping resistor was also open,
> which is odd since it was a 1 watt unit.
> 
> The transmitter is working fine now, but I wonder if I shouldn't go back
> and find a way to squeeze 1 watt resistors in place to avoid future
> problems, now that I've done the numbers.  Any suggestions?
> 
> 73 Bob W9RAN
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