HP 20s Calculator Screen/Keyboard Repair
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- čas přidán 11. 09. 2024
- Again, the common problem with this series of HP calculators where the foam pressing on the connection ribbon deteriorates and makes the keyboard so it will only operate if the bezel is pressed.
This video is almost identical to the HP 32sII repair video, but more detailed. Don't do like I did and bend the top half of the calculator!
6 years later and this was still the best video I needed to see to fix an HP 17B business calculator! Same case, same problem with the foam aging out! The double layer of Scotch brand mounting tape was perfect! Thanks for an excellent repair video!!!
Outstanding! So glad to hear. I didn't know if it would help anyone when I uploaded it but figured, why not? The response has been more than I imagined.
Thanks for the video. It gives me hope for my beloved 20S I've had since the 80's. My 20S was acting irradically, for instance, sometimes adding 2 numbers correctly, but at other times ignoring the + sign in 2+3 and showing just 23 and waiting for the next command. Soon I will get up the gumption to actually do what your video teaches. Thank you.
6 days later. well, I did everything as shown in ths video except I also drilled the 2 stubs near the batteries, as mentioned below by one of the commentors, which made it much easier to take apart. The first time I did everything as shown in the video, and when I got it all re-assembled and put the batteries in I got the same "All CLR" message, but when I tried to do some simple calcs it still had trouble "seeing" all of the key strokes. So I reassemble it again, put new foam stripes in as shown here, put it back together again, and Ka-Bang it looked like everything worked. I was happy! Two day later I thought I do some calcs, and found that now none of the keys responded, only showing 0.0000.
So I give up. HP, that design is so Mickey-Mouse, so disappointing. ....contacts via pressure? rivets vs 4 screws ....anyway, it did work for a while.... interesting exercise.
Thank you so much, Logan. My beloved HP-20 has risen from the dead! I was about to throw it in the trash, when I thought I'd do a quick search on the net, and immediately found your video. The fact that you do every step in real time was most helpful. I simply followed you step-by-step, pausing the video while I imitated your actions. In our throw-away world, we badly need guys like you to help us rescue equipment that is easy to repair, but only if you know how. I would have never figured out how to even gain entry to the calculator with your specialist knowledge.
That's outstanding, Jack. I did this video thinking that it was unlikely anyone was ever going to want to watch it to repair an old calculator but it's encouraging to see there are people out there who would rather take something apart and fix it than just throw it away. I wouldn't say I have specialist knowledge though, I'm just a tinkering engineer!
It helps to drill out the heads of the top rivets first, makes them much easier to pop which reduces the risk of bending the top. When reassembling the calculator, I screwed some small countersunk screws in the holes of 2 of the rivets, this makes it as solid as it was originally.
Since I don't trust any of the replacement foams not to degrade over time as well, and given the limited number of times that those PCB clamps can be bent, I 3D printed a replacement for the foam using TPU (NinjaFlex) which I expect to maintain its elasticity for much longer. A bar of 46.00 mm long, 2.75 mm wide, and 2.75 mm tall is a good size, at least for my version of the 20S. I printed it nearly hollow to keep it springy.
It looks like there are multiple variants of the 20S and yours is more recent. Mine has the CPU silicon die suspended in free air with some fancy mounting device, and the LCD has contacts at the top and bottom.
What I really like about this calculator is that with moderate use, it easily lasts about 10 years on a set of 3 LR44 batteries. They did a pretty good job at optimising power consumption.
Wow. Impressive.
Drilling out the top four rivets seems like a good way, but how did you deal with the bottom four which are masked by the cover plate?
The case aesthetics took a bit of a hit doing this, but the important thing is that it now works perfectly. Much appreciated.
Yeah, hopefully you managed to learn from my mistake in this video and did it more like my 32sII video :)
Great job, it helped me a lot. Thank you very much for for posting this video in the you tube.
You're welcome!
Thank you very much for sharing your knowledge. I have saved my beloved HP 20.
That's great! Very glad it was a help to someone.
Those top 4 can be freed by using a 0.147 drill and drilling in about 1/32 of an inch or a millimeter.
Well, I greatly appreciate your detailed video which gave me hope that my DOA calculator that set me back almost $50 with shipping and tax might be saved. I see a lot of happy comments below, but boy am I disgusted with the engineering design and quality of this calculator. It's ridiculous that they relied on such a terrible connector scheme to begin with, with compression and/or corrosion eventually causing all these failures. With the help of the drilling comment below (great idea), I was able to get mine apart without damaging it, which otherwise looked unlikely (it did NOT want to come apart!). I then proceeded to clean the contacts with 99% isopropyl alcohol, but the PCB pads remained very dirty looking. My ohmeter was reading about 45 ohms just probing two close spots on the same ground pad! I tested it, and it still did not work. I cleaned it one more time, and then thought I should measure the resistance on the flexible cable pads too--only to discover that most of them were literally gone in the middle! On the longer traces I was able to repeat the same-trace conductivity test, and basically the coating on these traces was an insulator. How was this ever supposed to work reliably? Now, thanks to the cleaning attempt, the traces on the cable are ruined and it's basically impossible to fix now, it's totaled. FYI, I'm an electrical engineer of nearly 40 years, I know a bit about electronics. I just wanted to share my story so that others don't think this is just easy and safe, it is not, and frankly I'm not sure I would value one of these badly designed calculators anyway, I'll collect other machines instead.
Very helpful video. I just drilled out the 4 rivets by the battery, very easy. I wasn't sure what was holding the bottom of the case. Those 4 rivets have to be popped as you showed.
Thanks - my 20S hasn't worked this well in 5 years!
That's great!
Hi Thanks for this - I was able to bring my 10B back to life , to open the top of the case and pop the rivets at the top I forced and old credit card into the case at the top and then a second one then using the cards to protect the case pushed in a medium flat blade screwdriver in between the cards - one twist and it pops open and distributes the force down the case, thanks again without your video i would have had no idea how the case was held together or where fragile components were located and would have probably wrecked my 10B
That's a great suggestion Steve, and I'm glad the video was helpful in some way.
Great fix! Must say the 20S is my oldest tech and still works great.
Dear sir,
It is a fine job. Working and not difficult to do. tnx for the instructions, Henry
Great tutorial! I was able to fix a $1 goodwill 20S with this technique. Thank you.
That's great! Glad to hear it and nice deal you got there.
Wow, This was not meant to be taken apart. You need to apply some force to pop those plastic rivets. Amaze the board still works. Worth a try if calculator is dead. But there is a 50% chance of cut fingers especially on the key board rivets the top can be drilled for easier removal..
Thanks for the video. Do you have video to repair contacts of 4 keys (0, 1, 4 and 7) in HP15C calculator?
Nice video! I'm about to try this on a HP-22S. Maybe I'll record it if all goes well.
Great video, thanks! I have opened a 42s using this technique but it took a lot of force to pry the bottom rivets off and the top plastic frame is bent by a millimetre or two. I probably shouldn't have shaved off the bottom rivets as much as i did as they don't snap together with the upper frame when I reassemble the calculator, and because top frame is bent a bit there's a permanent gap at the bottom. Any ideas on how to straighten the top frame other than perhaps putting it in a press for a few days. Cheers.
Why did HP have to make it so difficult to open?
Great job!
20s is broken I need help with it, I have a crack on the screen and I really want to fix it
Hi, and thanks for this; there's nothing like actually seeing this done! I've watched your 32SII key-repair video and this one; and I have a similar, but somewhat different problem.
It's a 32S (not 32SII), that is 'bricked' after getting accidentally knocked on its screen; so I suspect the LCD or its connection to the rest of the calc. And before that accident, no problem.
I tried the sub-screen bezel pressure you've demonstrated, to no effect, which is why I don't suspect the keys. And BTW, the screen looks normal; there's no visible damage where it got knocked.
I'm really wary about popping it open, but I'm ready to try just about anything. But is there a different part of the innards I need to attend to for a LCD screen problem?
Fred
Fred, the short answer is that I'm not sure, but the LCD connects to the rest of the calculator via pressure on a flexible connector (essentially what I'm fixing in these videos is the connection from the LCD to the rest of the calculator). It is conceivable that the blow misaligned the connector. At this point, opening it up can't make it worse so I'd open it up, see what you find, and go from there.
Thank you for your reply. I'll try it then.
Fred
Hi, what did you used for cleaning it?
Isopropyl alcohol or something like that should work.
@@west Thank you!
Thanks for sharing! Do you know how can I clean/fix the black screen of my HP 20s?
What do you mean by "black screen"? Does it not turn on?
It turns on... show the numbers... but the screen is dark... I forgot my calculator on the sun, and now the screen is dark.
Oh. Well I'm not an expert on that but I would suspect the LCD was pretty much roasted. The only repair would be replacing it, in which case you might as well get a "new" one.
Logan West That's what I thought too... Well, thanks again! I will try to find some calculator parts to replace it!
Any idea how to find the manual in English for it?
Alan Lilja hpmuseum.org sells manuals for all HP calculators in PDF form.
Same for 50g?
I don’t know but I suspect there will be some significant differences. If you do it, record your process and perhaps we can all learn something!
Logan, if I sent you an old hp, do you think you could try and repair it ?! Jrhernan @excite
Thanks for asking but sorry, no. I don't really have the time or desire to do that.
DESTROIER
If it ain't broke, don't fix it. If it IS broke...break it more!