Calculator button not working

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.

Reply to
Cursitor Doom
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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 c ontrol rebuild kits , around 20 bucks , that will resurface the carbon on t he rubber bubble. Good luck with it and I suspect you will be okay with the easy fix of alcohol and a cue tip.

Reply to
John Heath

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? :-/

Reply to
Cursitor Doom

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

Mikek

Reply to
amdx

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

Mike.

Reply to
MJC

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

Reply to
Cursitor Doom

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 :

Reply to
John Heath

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

Reply to
N_Cook

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This reminds me. Take a cell phone picture of the front of the calculator f irst before disassembling. All the buttons will fall out making it a challe nge to put them all back where they belong without a picture for a guild. B een there done that and I paid the price for not taking a picture before ha nd.

Reply to
John Heath

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

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.

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Reply to
Kenny Cargill

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.

Reply to
Ian Field

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

Reply to
Tim Schwartz

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The IR receiver in the TV or stereo is a standard part with 3 leads GND , 5 V , and data out. Standard as they all work at 34 KHz , same frequency as t he 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 pic k up IR from the remote control to see if it is working or not.

Reply to
John Heath

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.

Reply to
Ian Field

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 snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

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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 control s could do the same with one format only and a data header of the serial nu mber 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 r emote control. What is in it for them.

Reply to
John Heath

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.

Reply to
Cursitor Doom

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

Reply to
amdx

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.

Reply to
Ian Field

dude it was little helpfull for me. I removed stucked rubber of the buttons on the circuit witch the screw drivers nail - point and it worked. Thanks.

Reply to
alam.rashid039

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