On Jun 27, 11:54*pm, wrote:
On Sat, 27 Jun 2009 07:54:25 -0700 (PDT),

" wrote:
I was asked to look at an old lady's garage door opener. She says that
the opener works from the button inside the garage but the remote does
not. It just happened yesterday and it seems like we've had some
lightning come through the area over the pasr few days as well. Her
failure may be more than coincidental. I recall working on a couple of
openers several years ago during the Summer months that had damaged
photoelectrics after a storm. What I can't remember though is how to
positively determine that the photos are bad and not the radio system.
I don't know which brand opener we're dealing with if it matters. Can
anyone familiar with these systems please offer some insight into
this. Thanks very much. Lenny

If I'm not mistaken the remotes by design stop working if the photo
cells are mis-aligned or dirty.

The unit was a 1992 Craftsman brand opener. There are no dip switches.
The transmitters are "learned" into the receiver. There were two
remotes with this system. The photo cells were working, btw. One
remote she keeps in a drawer so it is rarely used. I made sure the
batteries were good and tried each transmitter. Neither remote
activated the onboard led on the receiver board. I then tried erasing
the codes and then reprogramming the receiver. It still wouldn't work.
With two transmitters doing this the problem is probably the receiver
however you can't really tell if the transmitters are putting out can
you? So how would you determine if both transmitters are good or if
the receiver were good? Without being able to duplicate the modulation
scheme, the best I could do if I could determine the operating
frequency would be to hit this thing with a burst of CW from a signal
generator. I know that this would not operate the door but would it
disturb the onboard led thereby indicating the presence of RF being
received? How about if I take the transmitters and put them in close
proximity to my counter and if the transmission duration is long
enough I should be able to read the carrier? Lenny.