I have a 1972-vintage Sears garage door opener, model 139.654000 which still works great. But the only remote I have left is falling apart, and is no longer dependable, particularly in very hot or very cold weather.
The transmitter/receiver system is the old analog type - no digital codes at all, just the specification of "carrier frequency" and "modulation frequency", and the receiver is powered by 24VAC provided from the main chassis. In fact, it appears that the receiver actuates the opener mechanism by at least partially shorting out its own power supply temporarily.
I have been unable to find any direct replacements for either the transmitter or the receiver. In fact, I don't really see any total replacements for the transmitter/receiver system that would operate using the 24VAC power supply.
Does anybody have any suggestions for what to do? I'd like to avoid having to replace the entire opener.