Re: Osborne 1 keyboard repair - success!
On Sat, 21 Nov 2020, Pete Turnbull via cctalk wrote: On 20/11/2020 17:59, Tom Hunter via cctalk wrote: Hi Patrik, As to the superglue - it was the only option because the prongs are just melted flat. To get the key mechanism out or off I had to scrape all the melted plastic off. I then subsequently re-attach the key mechanism to the aluminium backing board by applying a tiny drop of superglue between what was left of each prong and the associated hole in the aluminium backing plate. The key mechanisms can be pushed out again with moderate effort if it is ever necessary again. Another way to do this is, or to repair any heat-staked plastic, is to use a cheap 3D printing pen with the sample ABS or even PLA filament they usually come with. Now this is the first actual sane use of one of those things I've seen! Excellent idea! g. -- Proud owner of F-15C 80-0007 http://www.f15sim.com - The only one of its kind. http://www.diy-cockpits.org/coll - Go Collimated or Go Home. Some people collect things for a hobby. Geeks collect hobbies. ScarletDME - The red hot Data Management Environment A Multi-Value database for the masses, not the classes. http://scarlet.deltasoft.com - Get it _today_!
Re: Osborne 1 keyboard repair - success!
On 20/11/2020 17:59, Tom Hunter via cctalk wrote: Hi Patrik, As to the superglue - it was the only option because the prongs are just melted flat. To get the key mechanism out or off I had to scrape all the melted plastic off. I then subsequently re-attach the key mechanism to the aluminium backing board by applying a tiny drop of superglue between what was left of each prong and the associated hole in the aluminium backing plate. The key mechanisms can be pushed out again with moderate effort if it is ever necessary again. Another way to do this is, or to repair any heat-staked plastic, is to use a cheap 3D printing pen with the sample ABS or even PLA filament they usually come with. Lurid colours are optional with this technique ;-) -- Pete Pete Turnbull
Re: Osborne 1 keyboard repair - success!
Hi Patrik, As to the superglue - it was the only option because the prongs are just melted flat. To get the key mechanism out or off I had to scrape all the melted plastic off. I then subsequently re-attach the key mechanism to the aluminium backing board by applying a tiny drop of superglue between what was left of each prong and the associated hole in the aluminium backing plate. The key mechanisms can be pushed out again with moderate effort if it is ever necessary again. Best regards Tom Hunter On Sat, Nov 21, 2020 at 1:36 AM Patrik Schindler via cctalk < cctalk@classiccmp.org> wrote: > Hello Tom, > > Am 20.11.2020 um 15:11 schrieb Tom Hunter via cctalk < > cctalk@classiccmp.org>: > > > I have managed to completely disassemble the bad Osborne 1 keyboard > > Congrats on that! > > > The silver tracks remained undamaged as confirmed with a multimeter. > > Very wise to check this while all is disassembled. > > > I then carefully reassembled the 3 layers, inserted and super-glued the > keyboard mechanisms in batches, testing after each batch. > > When using super-glue, will this possibly negatively affect the ability to > disassemble the keyboard again? As far as I’m aware, the prongs are most > often just pressed flat with a hot iron to melt and thus held in place. > > > I did not use any glue to reattach the 3 membrane layers so they are > held together only by the keyboard mechanisms with their prongs protruding > through the layers into the aluminium backing plate to which the prongs are > super-glued. > > Very good idea! > > > The conclusion is that membrane keyboards can be fixed if your life > depends on it. It is absolutely uneconomic though. I worked about 30 - 40 > hours on the keyboard alone. Working Osborne 1s sell for between US$100 and > US$300 on Ebay. > > Well, with some routine you can become an expert and do that repair in 1-2 > hours. All membrane keyboards are very much alike. While I’m truly appalled > to do this for a living, I’m not frightened about doing this anymore. ;-) > > :wq! PoC > >
Re: Osborne 1 keyboard repair - success!
Hello Tom, Am 20.11.2020 um 15:11 schrieb Tom Hunter via cctalk : > I have managed to completely disassemble the bad Osborne 1 keyboard Congrats on that! > The silver tracks remained undamaged as confirmed with a multimeter. Very wise to check this while all is disassembled. > I then carefully reassembled the 3 layers, inserted and super-glued the > keyboard mechanisms in batches, testing after each batch. When using super-glue, will this possibly negatively affect the ability to disassemble the keyboard again? As far as I’m aware, the prongs are most often just pressed flat with a hot iron to melt and thus held in place. > I did not use any glue to reattach the 3 membrane layers so they are held > together only by the keyboard mechanisms with their prongs protruding through > the layers into the aluminium backing plate to which the prongs are > super-glued. Very good idea! > The conclusion is that membrane keyboards can be fixed if your life depends > on it. It is absolutely uneconomic though. I worked about 30 - 40 hours on > the keyboard alone. Working Osborne 1s sell for between US$100 and US$300 on > Ebay. Well, with some routine you can become an expert and do that repair in 1-2 hours. All membrane keyboards are very much alike. While I’m truly appalled to do this for a living, I’m not frightened about doing this anymore. ;-) :wq! PoC
Osborne 1 keyboard repair - success!
I have managed to completely disassemble the bad Osborne 1 keyboard - remove all key mechanisms (body, plunger, main spring and actuator spring), remove the 3 layer membrane from the aluminium backing board and separate all three membrane layers (bottom, spacer and top) - all without damaging or losing any bits. I then carefully cleaned off all adhesive and other sticky gunk from all layers using various solvents including water, isopropyl alcohol and white spirit. The silver tracks remained undamaged as confirmed with a multimeter. I then carefully reassembled the 3 layers, inserted and super-glued the keyboard mechanisms in batches, testing after each batch. I did not use any glue to reattach the 3 membrane layers so they are held together only by the keyboard mechanisms with their prongs protruding through the layers into the aluminium backing plate to which the prongs are super-glued. I sealed the edges around the membrane using Kapton tape to provide protection from dust etc. The tape also attaches the membrane edges to the aluminium backing plate. All keys except the "Alpha Lock" key work perfectly. It appears that I have damaged the address line 7 on the bottom membrane. I can live without "Alpha Lock" so I did not pull everything apart again to fix this un-important key. The conclusion is that membrane keyboards can be fixed if your life depends on it. It is absolutely uneconomic though. I worked about 30 - 40 hours on the keyboard alone. Working Osborne 1s sell for between US$100 and US$300 on Ebay. Regards Tom Hunter
Re: Osborne 1 keyboard repair?
Hello Al, Am 21.09.2020 um 14:08 schrieb Al Kossow via cctalk : > you might be able to change something if you can inject a solvent into the > side of the switch by drilling through the top layer And then, the solvent is meant to stay there? I had bad experiences with "put magic fluid in between and the problem will be gone". :-) Depending on solvent, the solvent has no chance to evaporate away between the plastic layers. And if it could evaporate, the dirt has moved around but not away. Also, letting solvent staying on these delicate conducting silver strips is most likely doing more damage over time. Also, depending on solvent. :wq! PoC PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc
Re: Osborne 1 keyboard repair?
On 21/09/2020 12:41, Tom Hunter via cctalk wrote:
The problem I am seeing is that 3 keys ("h", "j" and "y") are permanently
pressed.
I'm not familiar with this keyboard, so despite having fixed lots of
other types, what I'm about to write is no more than musing and may be
inapplicable drivel, but...
A friend once spilled a glass of wine into his keyboard and had a
similar problem. I've seen the same from a cola spillage. Washing it
fixed it. Can you see if there are any spillage residues in there? IPA
isn't always better than water and detergent - though you might want to
use it as a water removal agent afterwards.
As I imagine you've already realised, the keys are adjacent and likely
share a track.
I looked at the pictures. Can you get at the other side of the circuit
board? If the it's fibreglass or even SRBP with copper tracks, maybe
you can get at the tracks to the 'h' etc keys and cut them with a
scalpel or craft knife to isolate them to see where the resistance
really is. Before cutting anything, obviously make sure you can get a
soldering iron in there afterwards to bridge the cuts.
--
Pete
Pete Turnbull
Re: Osborne 1 keyboard repair?
On 9/21/20 6:41 AM, Tom Hunter via cctalk wrote: I cleaned the now exposed membrane using Isopropyl alcohol - no change in resistance. I don't think you've really exposed anything, have you? The membrane is going to be three layers - a bottom layer with traces on the upper side, a spacer layer, then the top layer with traces on the underside; you're looking at the top of the membrane from the "outside". I expect it's all heat-staked together, but it might be possible to dismantle, separate the layers, clean the conductive surfaces and the spacer, then reassemble. My guess is that what happens is either: a) repeated keypresses over time result in some conductive material wearing off and depositing itself on the spacer, eventually bridging the gap and registering as a short/press. b) corrosion of the conductive surfaces results in the same thing. Either way, cleaning would likely fix it - but only if the membrane comes apart; it may well be sealed together at the edges. Alternately you might, I suppose, be able to drill a small hole through the membrane close to the problem area and inject some cleaning solution between the layers that way, but I don't know how successful that would be. cheers Jules
Re: Osborne 1 keyboard repair?
Hello Tom, Am 21.09.2020 um 13:41 schrieb Tom Hunter via cctalk : > Has anyone got experience repairing or restoring this type of membrane > keyboard mechanism used in the Osborne 1 and probably in other keyboards too? Not with the Osbornes, but with others. This kind is cheaper to manufacture than the ones with "true switches". Anyway, to get rid of the problem, carefully heat the ground plate to "does not hurt if I touch it for 10 seconds" and remove all the spring housings. Punctual further heating is most likely needed. This enables you to separate the sheets, and clean them. This should remove remains of soft drink spills (possibly explaining your particular problem), as well as insulating black silver sulphide layers. I Germany we have a very mild solvent for electronics, proved to do wonders to this type of partly-conductive foils. https://www.amazon.de/KONTAKT-CHEMIE-71809-Tuner-Kontaktreiniger/dp/B000NI2NTA Maybe there's something similar where you live? Also, carefully inspect the foils if there's some mechanical damage, like dents on the actual contact spots, providing a contact all the time. If there are, there's some creativity needed to even them out. I never needed to do that. > Here are some good and detailed photos of keyboard mechanism: > > https://www.flickr.com/photos/123564336@N03/sets/72157644113347562/ Thanks, this helped a lot! :wq! PoC PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc
Re: Osborne 1 keyboard repair?
On 9/21/20 4:41 AM, Tom Hunter via cctalk wrote: I cleaned the now exposed membrane using Isopropyl alcohol - no change in resistance. https://deskthority.net/wiki/Membrane_keyboard#Spring_over_membrane you exposed the top of three sheets. the contamination/deformation is between the two outer sheets many people have complained about switch failures in osborne keyboards it is probably corrosion between these switch layers you might be able to change something if you can inject a solvent into the side of the switch by drilling through the top layer, but just a solvent on top will do nothing
Osborne 1 keyboard repair?
I am trying to figure out if it is possible to repair a Osborne 1 keyboard.
The keyboard is made by "Oak Switch Systems" and the type is FTM or "Full
Travel Membrane".
The problem I am seeing is that 3 keys ("h", "j" and "y") are permanently
pressed.
I did some experiments with the "h" key.
I measured about 20 ohm across the matrix pins for the "h" key.
I pulled off the "h" key keycap and the white plastic plunger with the both
large and small spring - no change in resistance.
I cleaned the now exposed membrane using Isopropyl alcohol - no change in
resistance.
I applied moderate heat using an electric hair dryer to both sides of the
area around the "h" key - no change in resistance.
I then used a lab power supply set to current limit hoping to zap whatever
is causing the partial short (20 ohm). I slowly increased the voltage and
current limit in short bursts until I hit 100 mA before I gave up the
experiment not wanting to destroy the two flex PCBs feeding into the
membrane. They did get warm but not hot.
I have run out of ideas of what else to try. I still measure 20 ohm across
the two keyboard matrix pins associated with the "h" key.
Has anyone got experience repairing or restoring this type of membrane
keyboard mechanism used in the Osborne 1 and probably in other keyboards
too?
Here are some good and detailed photos of keyboard mechanism:
https://www.flickr.com/photos/123564336@N03/sets/72157644113347562/
Thanks
Tom Hunter
Osborne 1 keyboard
https://www.elecshopper.com/osborne-1-keyboard.html I have no way to test it. Cindy Croxton Electronics Plus 1613 Water Street Kerrville, TX 78028 830-370-3239 cell sa...@elecplus.com --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
