[R-390] R-390A Ballast tube (RT510/3TF7) replacement options document

[Larry H]

Hi Jim, Good point on heat for the R-390, but I don't think heat is a big
issue on the R-390A.  But, I'd think that if someone were trying to resolve
the heat issue on the R-390, there are much more effective ways, like the
B+ regulators and the B+ rectifiers.

Regards, Larry


On Wed, Jul 26, 2023 at 8:56 AM Jim Whartenby via R-390 <
r-390 at mailman.qth.net> wrote:

> An observation:The only solution presented so far that addresses excess
> heat in the R-390 and R-390A is to upgrade to a 12BA6 in the oscillators
> and use a jumper in the ballast tube socket.  The 12BA6 has the same heater
> power as the 6BA6 and removing the ballast or it's substitute removes a
> source of heat from the radio.  In other words, the oscillator heater power
> is cut in half from 7 watts to 3.5 watts.



> Regards,Jim



> Logic: Method used to arrive at the wrong conclusion, with confidence.
> Murphy
>
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