Dave wrote in message
news

"Arfa Daily" wrote in message
...

"Dave" wrote in message
netamerica...

"Adrian C" wrote in message
...
Dave wrote:

Hey again,

Hard to know where to start, but I suppose I should begin here by
mentioning
that this intercom unit interfaces with the microprocessor controlled
device
over his bed (called a Quartet) which gives him control over the opening
of
the door, the operation of his telephone (to answer or make calls) and a
host of other tasks, all by voice operated control. It is more than a
simple intercom, even if that's what I call it. Doorbell-Phone is the
name
of the company that manufactures/sells this device. I forget the model
number. I will see if I can get a picure of the board to upload to
A.B.S.E.
As for the power resistor, it appears to be a five-watt or so, but seems
to
be dissipating something like 25 to 30 watts of power. The cap, if I
recall
correctly, appeared to have overheated. Originally thought it was
probably
shorted and that replacement would correct the failure. Replacement only
put a new (also high-temp) cap in it's place. Also replaced the
audio-amplifier transistor associated with that cap, and observed that the
overheating resistor was still far, far too hot to touch. The two
resistors
next to that one, of similar type, were barely warm. Following the
circuit
back from the resistor/cap/transistor led me to the 18-pin IC in question.
And I could easily be wrong about it being a PLL. I honestly forget now
what led me to that conclusion, as it has been several weeks since I last
worked on the device. I am hoping to get my scope down there and check
the
one pin for a clock pulse and the other for continuity with ground to see
if
it *could* be either of the two PLLs I have identified as possible
replacements for that chip. If that doesn't pan out, I'm out of ideas.
As
you point out, it *could* be nearly anything.

Thanks,

Dave




If zapped by electrical storm , why is most of the system still working?
Please put any pics on a proper website,eg the the one I use below is quick
and easy to set up, at no cost.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/