[R-390] Differences in 390A IF decks

[Tim Shoppa]

> The tech manuals mention differences between older and newer 390A
> IF decks, and folks here have, in the past, brought up that older
> Collins decks were different.  Indeed they are.
> http://www.fernblatt.net/forradio/R390A/

I assume you're talking about the fixed rather than variable caps
around the filters?

I have an IF deck that is Motorola and has the fixed caps too.  Not
sure if it was originally that way from the factory or was a result
of parts-swapping at the depot, but I was always under the impression
that many Motorola IF decks lacked the variable caps and the chassis
holes.

What exactly is that doo-dad in the ballast tube socket?

Tim.