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,JimLogic: Method used to arrive at the wrong
conclusion, with confidence. Murphy
On Wednesday, July 26, 2023 at 09:56:15 AM CDT, Jacques Fortin
<jacque...@videotron.ca> wrote:
Hello Larry,
I just seen my name mentioned on the 1st page of your document for the RT510
about the 2HTF11B.
That came from the fact that when I "found" my R-390/URR, it was equipped with
a 2HTF11B instead of a 3TF7.
And if you look in the Collins 1953 manual for the R-390/URR or in the
TM11-856, figure TM 856-10 in both cases, it can be seen on the picture that
the IF chassis bear the number *HTF11B for the RT510.
To "save" those ballast tubes, I have adapted the socket to use a 12BY7 in my
R-390 and R-390As.
No real difference, as reported by many others...
73, Jacques, VE2JFE in Montreal
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