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

[Larry H]

I've updated this document in two areas:
1. Added information about the usage of 2-12BA6's and no ballast tube will
save 3.5 watts of heat, as the result of a comment I received.
2. Clarified what happens when a diode alone is used instead of the ballast
or resistor or other solution.

Same link to it: R390A Ballast RT510-3TF7 tube.pdf (r-390a.net)
<https://www.r-390a.net/R390A%20Ballast%20RT510-3TF7%20tube.pdf>

Regards, Larry
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On Tue, Jul 25, 2023 at 11:30 PM Larry H <larry41gm at gmail.com> wrote:

> The R390A Ballast tube (RT510/3TF7) in the IF deck has been a very popular
> discussion item on the list forum, off and on for ever. And rightly so, it
> is expensive, not very reliable and somewhat fragile. This discussion is so
> popular that it has its own section in the 'Pearls' labeled ‘Ballast tube’,
> and what a section it is - 239 pages.
>
> The reason I wrote this document is that the discussions on the list forum
> are quite repetitive and the important information can be condensed into a
> few pages. Since it would take a person a very long time to go through all
> the entries in the Pearls and come to a conclusion, hopefully, this will
> save someone a lot of time.  My two page summary is at the end of the
> document.
>
> Here's a link to it: R390A Ballast RT510-3TF7 tube.pdf (r-390a.net)
> <https://www.r-390a.net/R390A%20Ballast%20RT510-3TF7%20tube.pdf>
>
> Regards, Larry
>