Vintage RailSounds (without TMCC), c. mid-1990's would do the trick for your vintage F3's, and will operate in conventional (transformer-controlled) mode only; just like them. How about a 'B' unit to go with them?
I know of one possibility, a ATSF B-unit with RailSounds II (6-18122). I have one so I have some experience with this. Unfortunately it's not PRR, but it is an F3 and it will do conventional RailSounds.
Three options:
1.) Find a 6-18122 and paint it (or have it painted) in matching PRR livery.
2.) Find a 6-18122 and transplant the innards to a PRR F3-B from the 70's or earlier if you can find one. This is only slightly complicated, primarily because one of the fans on the roof of the 6-18122 is the volume control.
3.) Assemble your own version of this in your dummy F3-A, instead of a separate B-unit. The schematic and exploded diagram for the 6-18122 is available here to get you started (see pages S32:2-4 and S32:2-5):
https://www.lionelsupport.com/...ent32/32Complete.pdf
Parts from the 6-18122 are largely also available at lionelsupport.com. See:
https://www.lionelsupport.com/...amp;CFTOKEN=48233349
Any of these would be an interesting project.
Mike
