Last winter one of the garage door openers stopped responding to the remote. After a week or two we had a cold snap and it started working again. Then not, then OK, more or less in sync with low temperature days. "Cold joint" says I. Then it finally died completely. Sears.com wants $85 for a replacement board (! you can buy a whole new opener for $135), so we lived with it through the summer as higher priority projects took precedence. Yesterday I tracked down the documentation, that includes a circuit diagram, so I finally took the board out and began searching for a cold solder joint. Found one: the pin on the connector that connects common on the board to the actual ground. Perhaps that could interfere with the RF reception. Resoldered it, but after reassembling the unit, found it didn't help. Got out the old Tektronix 'scope, climbed up the ladder, tied the scope onto a step and started systematically checking for signal. Eventually traced the signal from the RF receiver through signal conditioning to the input to the decoder chip. Signal goes in, right code, nothing comes out. Looked like an $85 part after all, 'cause I wasn't going to bother unsoldering the chip and finding a replacement. Before giving up, however, I moved all the DIP switches up and down a few times on the off chance that it was a poor connection inside the switch. That was it! Works fine now. Saved some bux.
Now, the opener on the other door, on which I did replace the board a few years ago, reads the code from the transmitter and memorizes it. No DIP switches. Unfortunately, ever few weeks it forgets the code so you have to do it again. A pain in the butt, but not worth replacing the board again for. If I can find a circuit diagram, perhaps I'll go after that problem too. It's been a long time since I trouble shot a circuit board. I'm inspired.
-- Bob (Chief Pilot, White Knuckle Airways)
I don't have to like Bush and Cheney (Or Kerry, for that matter) to love America