Just fixing my old model Sears garage door opener board, I see others out there have had the same issue.
I fortunately obtained a control board schematic many years ago, If all else fails, I may take a crack at writing a pic micro to replace the logic. especially if the receiver IC is still functioning.
I need to find the function of the 125C66 IC.
The other two are 125c42 which AliExpress has, and the third is 125C49 which decodes the received RF signal. the data for both of these do not seem to exist ?

 

Hello,

The same questions seems to be asked here:
https://forums.parallax.com/discuss...-on-two-texas-instruments-ics-may-be-obsolete

Bertus

 

Hello,

The same questions seems to be asked here:
https://forums.parallax.com/discuss...-on-two-texas-instruments-ics-may-be-obsolete

Bertus

Yeah, I found that also, does not help much though as no one seems to have found the functions?

 

Is this circuit schematic of any use to you?

 

Is this circuit schematic of any use to you?

That is the exact one I have.

 

Is this circuit schematic of any use to you?

A follow up.
Your schematic was not quite the same as mine, there were a few subtle differences.
Also I have two different versions of the board, and both of them differ from the two schematics slightly.
All appear to be interchangeable, there must have been a few versions of the board for the same ver of door opener?

 

Is this circuit schematic of any use to you?

View attachment 299101

I looked high and low for this. Many thanks for posting.

 

I looks like a house number for the IC.
In that era, National Semiconductor and Motorola had remote control encoder/transmitter and receiver MOS LSI chips.
MM53200 but different pinout, MC145027 different as well. I can't remember what Stanley used, look for their remote TX pics. You'd have to dig through old databooks.

I would suggest not keeping that because they are susceptible to replay attack and there aren't enough codes with ASK RF receivers constantly pounding out jibberish. Gotta hate when the door opens by itself lol. Also the RF band used may have a lot more going on in it, the frequency used might not be clean and that two-transistor receiver has pretty wide bandwidth...

Easier to bolt in a Holtek HT12 chipset but it is fixed code I believe.
You can buy rolling code keyfobs and receivers for better security.

I repaired an old Wayne Dalton garage door opener, it would cut out and stop opening sometimes. It was the tach opto-sensor had gotten old and weak, IR LED can easily accumulate 30,000hrs on it and they go dim. Controller uses speed to detect high torque like when it's squishing the cat it will slow down. Just a suggestion if you are in there.
edit: Also I shotgunned (replaced them all) the (~5) electrolytic capacitors, and all 3 relays for the $10.
It works great now and new openers are low quality and IoT dependant on a cloud server, just terrible I find.