In article ,
Andrew Gabriel wrote:
In article ,
jkn writes:
Hi all has anyone done any exploratory/repair work on these sort of
things? You know the ones, they operate in the 433MHz band I think,
and you set some DIP switches on both bell push and receiver so that
the codes match.

I know they are cheap rubbish, and the attrition rate is high;
nevertheless I am thinking of taking a closer look at one that has
stopped working. My first guess was imply that the press switch had
failed; but it's a PCB mounted switch with an ON resistance of 50Ohms,
which seems at least hopefull.

There is some failry shonky soldering, some of which I will probably
redo. There is also a little rust on a 3-wire metal cased part with
'433.920' marked on it; a SAW filter I assume? I guess this may have
failed, but the LED on the bell push doesn't go on when you press the
switch, and I think this is independant of the oscillator/transmitter.
Oh, and yes I checked the batteries...

As I say, not a big deal, but I'd be interested if anyone knows of any
common failure modes before I get in too deep...

Check for (and clean) battery contacts - corrosion on the permanently
live parts of outdoor electronics is quite common. Corrosion products
caused by battery leakage can be amazingly good insulators too.

I reckon if the switch is showing an on resistance of 50 ohms, it could be
the problem. Especially if the LED doesn't light. Could be proved by
shorting it out and seeing if the LED comes on.

--
*When a clock is hungry it goes back four seconds*

Dave Plowman London SW
To e-mail, change noise into sound.