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Posted to sci.electronics.repair
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Calculator button not working
In article ,
Ian Field wrote:
"John Heath" wrote in message
...
On Monday, December 28, 2015 at 4:43:01 AM UTC-5, Kenny Cargill wrote:
I used to fix TV's and with that came many faulty remotes. I dismantled
them, washed the membrane, buttons and case with Fairy or similar and
cleaned the carbon pads and PCB with Servisol switch cleaner and/or
isopropyl. Broken PCB tracks could with care be fixed, often with
conductive paint, and breakages around the legs of crystals & IR LED's
were
common and easily fixed or replaced.
Kenny
"John Heath" wrote in message
...
On Sunday, December 27, 2015 at 4:31:28 PM UTC-5, N_Cook wrote:
On 27/12/2015 16:04, Cursitor Doom wrote:
Hi all,
I have an elderly Casio scientific calculator (fx-3400p) which I've
owned
since new in 1991 (so I'm quite attached to it). Lately, the numeral
'2'
key has become a bit flaky inasmuch as every press doesn't always
register 100% of the time any more. I know these things are dirt
cheap
to
replace, but I've got used to the layout of it and don't really want
to
upgrade to something new if it can be fixed reasonably easily.
Any ideas what the problem might be?
thanks.
If its like my trusty solar powered fx451 from 1980s, used 20 times
today. To get
inside you pull the rear surround away from the case body proper, by
pushing your fingers through mock leather covering on the long edge
farthest fromthe hinge section. That edging traps the mock leather in
the gap between the 2 case parts
This reminds me. Take a cell phone picture of the front of the calculator
first before disassembling. All the buttons will fall out making it a
challenge to put them all back where they belong without a picture for a
guild. Been there done that and I paid the price for not taking a picture
before hand.
--- news://freenews.netfront.net/ - complaints: ---
The IR receiver in the TV or stereo is a standard part with 3 leads GND ,
5V , and data out. Standard as they all work at 34 KHz , same frequency as
the old audio ping remotes.
AFAIK: there are 3 inbuilt filter frequencies; 36, 38 and 40kHz and its
usually suffixed to the part number - not that they ever stamp it on the
physical part.
Having said that - I made a remote tester with a randomly selected sensor
from whatever equipment I scrapped last, it responds to all the remotes I've
used it to test.
Between them, the various manufacturers have used every possible permutation
for the layout of the 3 pins - when I salvage them, I leave them on the
front panel PCB so I can trace the tracks and figure out which pin does
what.
Digging out an old EEM catalog, the page for the Sharp modules has 9
different frequencies ranging from 32khz to 56.8 kHz. And I vaguely
remember the datasheet for the Temic(?) integrated circuit sensors
where the subcarrier frequency could be from 20 kHz to 95 kHz.
Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)
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