DIY Solid State Multiplex Adaptor Plans?

[Findm-Keepm]

The problem with finding a solid state adapter is that by 1967, all FM Stereo receivers were solid state, and mono FM was a rarity.

Every adapter I've ever run across is tube based.

You could try a FM MPX chip, such as the TDA7040T, a SMT 8 pin device with only about 10 external components, no coils or oddball parts necessary. Powers up with a 3V supply, and output impedance is pretty low, about 5K ohms. The whole adapter could be put in a matchbox.

in on pin 8, out on 5/6, pilot (stereo lamp signal) on pin 7, oscillator and low pass filter (both RC networks) on pins 2/3, and power/ground on pins 4 and 1.

http://pdf.datasheetcatalog.com/data...ps/TDA7040.pdf