HP 48SX Repair - Power On Failure -- Keyboard Failure
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- čas přidán 21. 08. 2024
- This video goes through the painful disassembly of a late 1980's era HP 48SX scientific calculator and the replacement of the rubber compression stripped used to aid in making the contact between the keyboard assembly and the main mother board. The symptoms for this failure can be that the calculator will not power on or there is intermittent or no operation on some keys. A quick check is to press bezel above the white function keys while pressing the on button. If the calculator turns on or the keys resume function, then the internal compression strip has deteriorated beyond reliable use and must be replaced. Please watch the video to learn how to replace that compression strip if the symptoms are the same.
I'm impressed by your calm trying to disassemble this nightmare to repair calculator. Incredible that it has such a beautiful PCB and performing calculator but is so hard to take apart compared to a TI.
I have an HP48G. Had the same problem. Found that other YT video about putting pressure under the LCD to turn the unit on. That works for me. Once the calculator is on, I don't need to apply pressure anymore, and it works fine. Sometimes I need to apply pressure to turn it off though. Lately the calculator has been working fine without the pressure trick. Very flaky. I must have a mild form of the problem.
my 48sx is the same way. only the on/clear button didn't work, but a few times pressing on it has brought it back to life and it's been working fine for 3 years. I don't know if I could stomach trying this once it finally dies. One ugly hack I've seen is using a rubber band to apply pressure under the screen
Thank you for this exposition, I've watched your video and also followed Pawel Golaszewski's "Open48" instructions that I found on hpcalc and I've managed to open my HP48G+ that wasn't working since I forgot I was using duraleaks, I mean, duracells on it and neglected to remove them for long term storage. The display was also darkening and since I had nothing to lose, I decided to try to open it. Took some patience due to the bottom part being very stubborn, if I had to do it again, I'd probably drill some holes on the battery compartment to get rid of the plastic bits that gave me so much trouble. But it worked with just a few marks on the side and a little warping of the face plate, that with some patience can be straightened.
Seems like the guy has an infamous younger homonym in another country, I was trying to find out if he had changed his e-mail in the last 22 years and didn't find what I was looking for.
Good luck with the repair. I decided against drilling mostly because I didn't want to deal with how to put it back together without the plastic snap fasteners. I expect that my calc may need to come apart again, and since the snap fasteners have been exercised once since it was manufactured, I expect them to be a bit easier the next time, if there is a next time.
Thanks for making this video. You're the first.
Just what I needed - thanks! It is a little hard to see what you're actually doing though.
Unfortunately the plastic snaps holding everything together are difficult to find and pop so not easy to show except when everything is apart. The rest should be easy to figure out with releasing the LCD screen by its twist tabs and changing out the compression strip.
I took the batteries out discharged the capacitor and reset it. Thank heavens it works.
I bought one a few years ago at a flea market for $5. Exact same problem. I just tore it apart to look at the guts. Too bad this video wasn't around then.
Thanks for this awesome teardown video. I have 48SX back in college year in the 90s, the LCD getting darker with first icon row "burntmark or bleed" . It could be due to aging or humidity.
Will dehumidifier or dry camera cabinet help to improve the LCD screen? I could still see the screen, but at brighter room.
Not sure if I need to use plastic plier to open this unit to clean the PCB with 99% isopropyl alcohol . Oh, one of the bottom battery twin- terminal has been loosen , I may need to glue it to the pad.
Thanks again
I have a HP48G+, not with Keyboard issue in yours, but mine has the reflecting layer on the LCD back completely failing (dark and transparent). So, although my calculator works electronically speaking, the Opticalpart of the LCD makes it unusable. Because of that, I need to open mine and I guess your method is less dangerous to other ones that disassemble from the front metal overlay. Please advise:
Any further suggestion, or tip before starting in this non-returnable trip?
I’m in Brazil and I don’t have such nice and robust plastic tools/levers, just regular flat screwdrivers and some wood-carving tools. To hold them on position while opening I could use several (expired) credit cards. Any further suggestion or warnings?
Thank you in advance for any remarks you could bring, and thank you for sharing your repair.
If you can find a plastic putty knife or scraper from a hardware store, that would probably be the same for sliding between the case and circuit board. Never use something harder than the plastic you are working with or you will end up making a mess of it. Hopefully you have a doner LCD screen...they seem to be hard to come by now. Make use of the hp museum website for any other instructions that are different between the SX and G. I think they are more or less the same construction. I would suggest you replace the rubber compression strip even if it does not seem to be deteriorated. Last thing you will want to do is have to pop that nightmare apart again.
Many thanks for Your exposition. I have been using an HP 48G+ scientific calculator for years. For a few days now, the monitor has been dimmed in the middle. Does it need to be replaced?
Can you help me solve the problem? Best regards
Could be the display itself, but more likely the zebra strips and pcb contacts need a good cleaning with alcohol. If it is starting to fail, the compression strip is likely at a point where it will need replacing too. Mine was only the compression strip however I did clean the zebra strips and contacts because I had it apart already.
Have same problem. Can you share the description of the Silicone foam you used.
Searched but too many choices for thickness and composition.
Appreciate any info. Thanks, BIll
I used the high temperature close cell foam from McMaster Carr similar to part# 51009k25. This has a adhesive backing on one side to make installation easy. I did double up on it though since it isn't that thick. The foam I have is about 0.07 thick.
@@powerevolutions Thank you for the info.
Hello, I have a similar problem with a 48gx, specifically it turns me on fine, but some keys don't work, pressing them does.
I am encouraged to repair it by following your video, but I have doubts about how you did to put it back together, did you break the rivets when you opened it?
It will snap back together but it is only a little less more difficult to do then it was to get it apart. I used a quick clamp to help put enough pressure on the case for the rivets to snap together again. You just need to be careful with the pressure.
@@powerevolutions Oh I understand, I thought that when opening it broke some rivets, I will dare to try thanks
@@cesargabrielarrietacarrasc3169 Think of it more like really strong lego that is near impossible to separate. So rivet may not describe it correctly. I don't think I broke any when I took mine apart.
@@powerevolutions After a lot of patience and measured strength, I was able to disassemble it completely!!! thanks for the video.
Now I have a doubt, because it is not very clear in the video, changing the rubber that connects the keys with the display of the screen, we are looking for the keyboard flex is fully supported on the same or is slightly detached?
I do not know if I make myself clear, if there was a way where you can send the image would be much more understandable.
In many ways the best calculator ever. Also, in many ways the worst calculator ever.
The fact that more or less all calculators get the infamous keyboard bug, along with being nearly impossible to open, a soft metal faceplate that WILL dent sooner or later, makes me stay away from it. HP really made some terrible design choices, probably to keep costs down.
The emulator is a good choice to get a pc calc that is RPN and still for the most part looks and acts like the real thing. No physical to wear out or get damaged. Funny enough I haven't really used it too much since I fixed the compression strip since I have used the emulator for 10+ years 😀
To give them some credit, 30+ years is a long time for a calculator to keep working--I doubt the imagined design lifetime was close to that. The biggest problem they had back in the day was that they were just too valuable--usually they'd get stolen long before they broke. That was how I lost mine.
I use an HP48 emulator on my phone for some daily calculations--though, honestly, most of the time I just use it as a basic RPN calculator, since for its advanced CAS and graphing capabilities it's more convenient to use Wolfram Alpha or a modern graphing-calculator app (or even Google). The one I had back in the day was a 48SX, and I have a hard time getting used to all the menu/wizard interfaces they introduced for the 48G, which were intended to make things easier but, to me, break the logical unity of the system. At least I finally figured out how to get arguments off the stack!
I ought to get back into RPL programming--it might still be useful as a programmable for automating repetitive calculations.
Where did you get your spudger, spatula, and prybar? They look 3D printed, but I don’t see a 3D print being strong enough to open the 48.
I used a Wetado 203 Pcs trim removal kit...works for trim, works for HP48SX. Just search "Wetado 203 Pcs" on amazon for the kit and you probably can find similar kits cheaper that will work just fine.
That’s excellent! Thanks for the quick reply. Those will be a good addition to my toolbox.
Those bigger tools remind me of the tools used to remove car trim parts from panels and doors for replacement.
The proper way to take it apart is to peel off the front aluminum panel.
So THAT's why some people try to pawn these off for stupid money with a rubber band around them. Not sure why anyone these days buys a used calculator for more than $20 in the first place.... we all carry one on us all the time.
There are a couple reasons I can think of off the top:
1. You can't use your phone in exams for school. so an emulator is out of the question.
2. A flat screen is no substitute for real calculators with real keys. Older HP calculators are unmatched in the quality of the tactile feedback. Haptic feedback buzz is not the same thing.
For casual calculations, an emulator is fine, I have several on my phone I use all the time; but when I'm doing real work I still reach for one of my physical calculators. It's just unfortunate the foam strip is the Achille's heel of the design and it's such a PITA to replace.
I love your work! go for it!!