"Bob Parker" wrote in message
...
I've been investigating intermittent temperature-related strange remote
control operation in a brand new SDT-9077P. When some buttons are pushed
and held down e.g. 'Menu', it behaves as though the button's being pushed
twice or more, very quickly.
Turned out that the 47uF electrolytic cap in parallel with the battery
had an ESR of 16 ohms and might as well not have been there. Replacing it
with a decent quality 220uF completely fixed the problem.
There are lots of complaints about this issue with the SDT-9077P on
various forums. Looks like a batch of defective electrolytics have found
their way into these remotes.
To open the case, push your thumbnail into the gap between the top and
bottom case mouldings at the end furthest from the IR LED, then carefully
pop the clips apart on each side until you get to the LED end.


Bob


Hi Bob. A bad electrolytic across the battery used to be a problem for all
sorts of remote controls a few years back. Seems that they drive the IR
LED(s) at a very high pulse current to get a long range, and the internal
resistance of the batteries is too high to allow them to supply it, so a low
ESR cap supplements them during the pulse peaks. Interesting the sort of
symptoms that you got from this one. Typical symptom from the ones that I
mention, was poor range. Maybe in the case of the Digicrystal, the battery
voltage was dropping low enough on the peaks, to upset the IR code generator
IC in there ?

Arfa