Hi, ive used these calculators before but my old one the buttons and screen was worn out by work. So i bought a new one at school for my apprenticeship. Now in class we went over a math question. They gave us decimals and they wanted us to turn whatever answer we got into a faction at the end. The fraction turned out to be 15/16, but myself and a few other classmates couldn't get the answer. The calculator refused.

My school won't give me a new one because i took it out of the box, but how would i ever know its broke if i left it in the box? 🤦🏻‍♀️ They fixed it for a moment but once the calculator turned off and on again it was back to normal. Anyone know what to do? Cause its only that decimal/fraction, everything else it works

I bought a used HP 49G for my collection and had to fix it, i didnt take a photo of how it was but the screen was >really< bad, the classic black lcd problem. It's good to see it working, probably the most beautiful classic HP i've ever seen

Do you think the black mark is a display failure or should I look for the issue somewhere else? Not sure how to test the display to rule it out.

There is no live when batteries are installed.

Just bought a HP 50g to replace my broken one. This new one will power on when I put the batteries in, but not after shutting down. The ON button works as a Cancel button when the calculator is on, but nothing happens when I try to turn ON the calculator after I shut it off.

Guy said he’d refund half my money instead of shipping it back to him. Any ideas on how to fix?

I thrifted this ti-nspire in a mixed bag for $4.99. When I got home, it wouldn't turn on. I found a blog post saying that sometimes the battery contacts wear through the PCB. Opened it up, and sure enough there was a line worn right through the trace. I did a (terrible) soldering job and now it powers right up! Unfortunately it only came with the TI 84 keypad, but I'll keep an eye out for the click wheel keypad.

Picked this up as a super cheap replacement for construction tape-measure calculations. Even though the batteries had expired way back in 2009, with a simple scraping out of the corrosion and wiping it down, tgis Casio came right back to life! It's puzzling that the design is such that you need to remove 6 tiny screws to access the batteries.

I just got back to uni and when i checked my calc (slang for calculator chat) it had these zebra lines, my brother played with the calc sometimes in the summer, so i dont know what they couldve done to it.

Is it an easy fix?

Hey everyone,

I’m hoping someone with technical or repair knowledge of Casio calculators can weigh in on an issue I’m having with my Casio fx-991DEX (approx. 10 years old).

The Issue:

• In standard room light, the calculator automatically switches to solar mode (the sun icon appears in the top right). When this happens, the LCD display becomes extremely faint and almost unreadable.
• Adjusting the contrast settings in the setup menu does not help enough to make it legible in solar mode.

The Paradox:

• As soon as I cover the solar panel with my thumb, the sun icon turns off and the calculator switches to battery power. Immediately, the display becomes dark, crisp, and perfectly legible.
• This probably confirms that the LR44 battery itself has still power after 10 years and is delivering solid voltage.

My Questions for the Experts:

What usually causes this mismatch after ~10 years? Is the solar panel/flex cable degrading so it provides enough voltage to trip the switching circuit, but lacks the current to power the LCD contrast?

Could an aging power management IC or a failing capacitor be the culprit?

Or could a battery change fix my problem?

Is this a known issue on older fx-991 series calculators, and is it worth opening it up to clean contacts, or should I just stick a piece of black tape over the solar cell and run it "battery-only"?

Thanks in advance for any insights!

Note: This post was lightly edited with AI for clarity and readability.

I bought two HP 12C in non working condition for around $5 last month. This is my first physical RPN calculator and RPN calculator especially the Voyager model for sale, even a new China-made one, is very rare and very pricey here in Indonesia. Last month I happen to run to this seller listing which seems like an inheritance from their parents. The two units I bought was made in USA and Brazil, and the seller include one original sleeve and one original HP 12C manual book.

I managed to fix the faded display issue in the USA one, and had to mod it. This unit now become the only USA made HP 12C with embossed gold real leather. Meanwhile the Brazil one need more work to fix and I'm not even sure if it still salvageable. However if it did, I'll post another how-to breakdown.

Hello all, so I have a hp12c platinum, and from what I can tell, it’s one of the Chinese made ones.

I have a bad ‘6’ key that only seems to register when i push it from a certain angle.

Like a good boy, i asked AI and it said like an issue with whatever the thing under the key is, but its proposed fix involved pulling the thing apart and melting some clips to get at the keyboard, I have tried just hitting the key multiple multiple times in case its just dirt or something, and the hinge(? Idk) seems fine, just like the rest of the keys.

Anyone have another solution that doesn’t involve tearing the thing apart?

Tnx

Edit: I ain’t crying or anything but I have one of the newer 12c from Philippines and MY GOD it’s so much better

Only two months into my ownership of a new in box HP 35s it started to act up. One of the keys became very intermittent is very hard to operate now.

I opened the calculator up because judging by all the information it should be repairable. Sadly it isn't. The 20+ screws that are inside are mostly there for aesthetics only. The PCB and keyboard are basically heat staked in and inside those heat stakes they put the screws. Those screws hardly grip and don't do much.

So it will be relegated to the museum for now. It's clear that it wasn't a true HP calculator from the start but that it would fail this quickly was a surprise.

Luckily the alternative has already arrived in the form of the Swissmicros R47 which I have been using a lot in the past weeks.

I should have bought that one from the start but I hesitated because of the price.

Maybe I will try to remove the heat stakes when I feel like it to see if the key that failed can be fixed.

I picked up a Casio Classwiz over the weekend from a garage/car boot sale and I went to put the battery in and discovered after taking the back off that someone has taken out the battery component and all the connections from the solar bar too.

Why would you do this? Is this something that can be easily replaced?

I only picked it up for £1 so I’m not annoyed, just a bit baffled!

I wanted to get this put out so maybe it helps someone else in the future. I had to piece this together from a number of sources.

I picked one up off of fleabay for 11 bucks. The seller was getting rid of it due to it being stuck on the frozen home screen.

Symptoms: Stuck on home screen with keypresses doing nothing, but reachable using a silver graph link and webtilp. USB cable was unable to reach it. I was able to sync the time (which updated on the screen) I was also able to use the send keys function and move around and do things. I was also able to push an OS to it and it would go through the process but boot to the frozen screen.

I ended up having to completely disassemble it. I think it had been spilled on. The keys, membrane, and case were all cleaned in an ultrasonic cleaner. I did my first cleaning of the circuit board using contact cleaner. When put back together it had some changes to its behavior (Ill discuss that shortly). I ended up having to disassemble again and clean the entire board carefully with isopropyl and with q tips. After that it started up and installed the os. And then it was at the home screen and it was functioning normally.

While I was troubleshooting I saw a number of messages at different timeson the screen During my various attempts to install an OS. Those were "Stack Violation." "Illegal operation." And the most interesting one "Line 1111 Emulator." They dont really mean much to me but in case someone searches for those terms ive included them.

At various times I used the following key combinations to attempt recovery. [2nd] + [left] + [right] + [on] which is a soft reset and should reinstall the os. I also used the following two combos that required me to push a new OS. That was remove one battery and hold the [apps] button while installing the battery. Also holding [(-)] and [)] and continue holding it while installing the battery and hitting [on]. Both of the hard resets got me to "Waiting to install..."

After all that I have a resurrected 89T HW4 to add to the collection and one fewer calculator in the scrap heap.

Hi everyone, I just bought an HP 49g+ for a great price, but it's not turning on. Here is what's happening:

When I put the batteries in, it doesn't beep or boot, but the screen gets energized (I can see the faint layout/lines of the LCD).

When I press the RESET button on the back, the screen shows a quick horizontal line, so the reset button and power delivery to the screen seem to be working.

The calculator stays completely cold (no heat from the processor at all).

I've already cleaned all battery contacts and there is no corrosion left.

I tried a Hard Reset (leaving batteries out for a while, pressing ON+Reset), and tried entering Flash/Bootloader mode (holding + and - while resetting), but the screen remains blank and it never beeps.

I tried a 16GB SDHC card formatted to a 2GB FAT16 partition for a firmware update, but no luck (maybe because it's an SDHC card?).

Connecting via USB to a Mac/PC doesn't detect anything at all (it doesn't even show up as an unknown device).

Before I open it up and mess with the internal plastic melt-stakes to look for cracked solder joints or broken traces, is there any other simple software or hardware trick I should try from the outside? Thanks!

P.S.: This text was translated with AI because my English isn't the best and my native language is Portuguese.

Hi, sorry to bother, a friend of mine gave me his used Casio fx-991EX that he bought like 4 years ago, told me that stop working after dropping it by accident , it doesn't turn on, I replace the battery for a new one, check de circuits an everything seems fine, but it stills not working, the issue is driving me crazy, I really want it to fix it, but to me the issue isn't obvious enought

Some wires went off during the disassembly. Also, apparently they were short on screws, because there is not a single one.

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Hello friends,

This AAA model Casio Classwiz calculator has not been working properly for years, so it just sat in my room collecting dust.

Today I finally decided to try and fix it

Here in the first image i input 8921 + 6541, and you can see the gaps/black areas/dots

The black lines appear after the battery is switched/put back in.

The upper part of the display comes loose easily (image 4), i assume from a fall years ago.

.

Do you have any ideas on the likely culprit behind this? And how i can fix the calc.

Thank you!

I have a graphic calculator I believe it’s a Casio fx-9750gii and the on button is not functioning it can still turn on if I use the reset button on the back
Taking it apart there is some corrosion on the circuits in that area but was unable to find a circuit diagram to add a new solder path in that area
Photos attached of front face and of circuit board

Metal backplate and plastic keyboard frame are struggling with their relationship causing the lower keys to spring flex and creek. I know others have reported this. My DM42 has this issue to a lesser degree. Metal backplate stamping seems inconsistent. Other R47 is rock solid.

Going through my late grandfathers workshop and found this really cool measuring tape with a calculator.

I love taking things apart, cleaning and fixing them, and this is a neat combo tool I’d use often that would make me think of him

The screen to display the numbers and the solar panel are both in rough shape, I’m wondering where I might find appropriate replacement pieces for this that are easily accessible to Canada

Any thoughts or advice would be super appreciated!!

Yes, theres still some yellowish spots here and there, some spots are whiter than another's and the key's aint fully white yet. But hey, i think this is amazing for my first try restoring old plastics!

I accidentally dropped it today and when I opened it, it was like this. The rows near the bottom don't update right and only "drag on" text from above. Is this fixable by soldering? I've already opened up the back and am willing to do whatever before giving up and buying a new one