[DavGoodlin]

Sure sounds like the local oscillator is not. Your Westinghouse uses the other half of the 12AT7 as the RF amp (instead of an oscillator) while using the 12BE6 as the oscillator for both AM and FM. Could this have been done to avoid a patent infringement on the "Armstrong system" ? Maybe some kind of upgrade is in order to get the 12BE6 to run at an abnormally high frequency. I would try swapping in as many different 12BE6's as possible.

My Motorola 79XM1 uses a 12BA7 (AM-FM osc-conv) with a 12BA6 RF amp, but barely functions on FM. I am not sure if this was the "Armstrong system" either. The tube characteristics show a 12BE6 and 12BA7 have an awful lot less Gm (gain) than 12AT7 as well.

My 1950 Zenith H724Z (a very common set with good reason) uses a 12AT7 as the FM AND AM oscillator with 6BJ6 RF amp. It has a gold sticker on the back proclaiming "the armstrong system". The selectivity is great for such an early FM.

BTW I will NOT own an RCA with FM solely because of Sarnoff's mistreatment of Maj. Armstrong.