Calculator button not working

[Cursitor Doom]

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.

[John Heath]

Try cleaning the rubber bubble carbon and PC board with alcohol and cue tip. Works for remote controls most of the time. Failing this buy the remote control rebuild kits , around 20 bucks , that will resurface the carbon on the rubber bubble. Good luck with it and I suspect you will be okay with the easy fix of alcohol and a cue tip.

[Cursitor Doom]

On Sun, 27 Dec 2015 09:04:26 -0800, John Heath wrote:

> Try cleaning the rubber bubble carbon and PC board with alcohol and cue
> tip. Works for remote controls most of the time. Failing this buy the
> remote control rebuild kits , around 20 bucks , that will resurface the
> carbon on the rubber bubble. Good luck with it and I suspect you will be
> okay with the easy fix of alcohol and a cue tip.

Thanks, John. I'm really loathed to throw this old friend out. Babies as
yet unborn when this was shipped to me have grown into men and gone out
and died fighting for the Queen in Afghanistan before this calculator
ever started to fail - and it's had some hard use, I can tell you. Makes
you think, doesn't it? :-/

[amdx]

I bet you feel that everyone around you is getting old.
I sure feel that way.

Mikek

[MJC]

In article <n5pb4f$n3k$1...@dont-email.me>, noj...@knology.net says...

>
> > Makes you think, doesn't it? :-/
>
> I bet you feel that everyone around you is getting old.
> I sure feel that way.
>
> Mikek

For myself, I knew it was not just me...

Mike.

[Cursitor Doom]

On Sun, 27 Dec 2015 12:39:35 -0600, amdx wrote:

> I bet you feel that everyone around you is getting old.

Those that haven't *already* died from old age, yes!

[John Heath]

We are not getting older. Its everyone one else that is getting younger. Just turn on the TV and you will see what I mean :<).

[N_Cook]

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

[John Heath]

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.

[Kenny Cargill]

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
news:24bea72f-83ac-4a88...@googlegroups.com...

--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---

[Ian Field]

"Cursitor Doom" <cu...@notformail.com> wrote in message
news:n5p7cu$di1$2...@dont-email.me...

With the conductive rubber backed buttons, I've got away with shaving a
sliver of it from a scrap button strip and sticking it on with RTV silicone
sealant.

The one that failed on the PVR remote was the right arrow button from
constantly scrolling through the EPG. Cleaning didn't help, and the
conductive rubber bit looked perfectly OK - but the grafted on replacement
did the trick.

Sometimes the contact pads on the PCB have overlaid screen printed link
tracks of some kind of carbon filled resin - these can be damaged by
solvents when cleaning them!

Some older calculators had the "popper" style button contacts - replacements
for those can be salvaged from some makes of disposable cameras.

[Tim Schwartz]

Hello,

In case your calculator is doomed, you might try looking on e-bay for
a exact or similar replacement. They don't seem to sell for much $, or
is that pounds?

Best regards,
Tim Schwartz

[John Heath]

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. With this in mind I put a IR remote receiver in a spare radio on the volume control. This way you can hear the data when a button is pressed. This is useful when you have the remote control only for repair. Another way around this is to use a cell phone camera. It will pick up IR from the remote control to see if it is working or not.

[Ian Field]

"John Heath" <heath...@gmail.com> wrote in message
news:aa92f31a-f9b2-4afd...@googlegroups.com...

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.

[Mark Zenier]

In article <rFAgy.373267$dK6....@fx42.am4>,

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 mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

[John Heath]

Not only the carrier frequency but the data format and baud rates change so that each manufacturer can have there own unique remote. My TV a Hannspree has such an odd remote format that it is not listed in any of the standard general purpose remotes from what I could google. You would think that the industry would standardize remote controls to one format. Wifi with IP and MAC addresses works fine with just one standardized format. Remote controls could do the same with one format only and a data header of the serial number of the TV or stereo you want to talk to just like a MAC address. Then again it is hard to corral all the manufacturers to agree on one standard remote control. What is in it for them.

[Cursitor Doom]

Finally got around to taking the thing apart. There was a tiny almost
invisible green-colored fibre no more than the thickness of a hair lodged
between the '2' ferrite core and its coresponding capacitive film backing
acetate pad. Had to examine it under a stereoscope to spot it it was that
tiny. Brushed it away and the pad's working fine again. That 1/000"
obstacle was the issue! Hopefully working again for another 25yrs now.
Thanks, all.

[amdx]

Back in the olden days, I repaired VCRs. I built a remote tester using
an end sensor from a VCR. It consisted of a 9v battery, end sensor,
resistor, plastic box and a couple of outboard connections for the scope
probe. Just point the remote at a hole in the plastic box and see the
waveform on the scope.
I fixed a lot of remotes at $29.50 each. The most memorable one was
on a remote I didn't find a problem with. The customer picked it up and
called from home saying it didn't work. I had recently read an article
in a trade magazine about new fluorescent bulbs (CFL?) overloading the
sensor in the VCR. I ask about lights, he said he had a new light, I
said shut it off, the VCR remote worked properly with the light off.
I suggested he move the light or build a shield between the light and
the VCR sensor.
I have a Sony remote that needs disassembly and pad cleaning,
this may provide the incentive I needed. :-)
Mikek

[Ian Field]

"amdx" <noj...@knology.net> wrote in message
news:n6tjqk$sh2$1...@dont-email.me...

Had a TV in a few years back - the fuse was "tombstoned" in its clip, I did
all the safety checks before refitting the fuse and the set worked
perfectly.

The handset made me earn my fee. A battery contact was off, it was filthy
and the left/right buttons were swapped over. It didn't look like much, but
the buttons didn't seat properly and were permanently pressed.

[alam.ra...@gmail.com]

- show quoted text -
dude it was little helpful for me. I removed stuked rubbers of the buttons on the circuit with the screw drivers nail -contact- point and it worked. Thanks