sporkme
drop the crantini and move it, sister
Premium,MVM
join:2000-07-01
Morristown, NJ
 ·Optimum Online
| Cleaning/Fixing Keypads
Hi all,
I've got an old 900MHz DSS phone that I do not want to give up - the range, clarity and lack of interference is great. 2.4 phones suck for interference with WLANs and 5.8 is just too short a wavelength to get good range through walls.
So my Uniden works great, but it has one of those membrane type keypads similar to what you'd find on a remote control or a cell phone. The top 2-3 rows of keys require an insane amount of pressure to register. Before I dig into it (again) and try to figure out what's wrong, does anyone have some tips on how to clean or repair (or is it alignment?) these things?
Here's my best effort at describing the keypad... The buttons themselves are all part of a rubbery pad that is one piece. The buttons themselves are raised on the front and poke through the plastic case. On the underside of each button is a black pad that kind of looks like a chunk of graphite. The pad lays directly on the PC board which has a circular pad for each button with two conductors that appear to get shorted together when the piece of graphite(?) comes down on them. If you ever took apart anything with a rubbery keypad, I assume you've seen all this... 
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with every mistake we must surely be learning |
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SparkChaser
BURY BECK
Premium
join:2000-06-06
Downingtown, PA
 ·Verizon FIOS
·Comcast
| You described it very well. I've fixed a lot of these in musical keyboards and some barcode readers. Usually it's a mater of cleaning the carbon pad and the PCB contacts. I've used non lubricating contact cleaner or isopropyl alcohol for this, use Q-tips. I also clean it with an eraser. The non abrasive "white" erasers. |
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sporkme
drop the crantini and move it, sister
Premium,MVM
join:2000-07-01
Morristown, NJ | Thanks... I'll give that a shot. I have both 99.9% isopropyl and some tuner cleaner. I'm guessing I probably brought this on myself with fingerprints or similar on the PCB. I've had it open a number of times to re-repair a flakey headset jack... |
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Tursiops_G
Technoid
Premium,MVM
join:2002-02-06
Norwalk, CT
clubs:
·Optimum Online
| I'd recommend using the 99.9% Isopropyl Alcohol, rather than tuner cleaner...
Tuner Cleaners usually also contain a Contact Lubricant (which is Fine for Mechanically "Wiping" Contacts), but may cause problems with Non-Wiping, Point-Contact Keypads... 
-Tursiops_G.
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If You're Unsure, "RTFM"... If You're SURE, "RTFM" Anyway.  |
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justsurfin30
join:2005-08-28
Nixa, MO | reply to sporkme
hxxp://www.chemtronics.com/products/product.asp?id=32
Try this, works on anything with a rubber keypad. |
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drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
clubs:
| reply to sporkme
I've done it many times. I take the whole thing apart, and wash the rubber keypad and plastic parts with water and a small amount of dish soap. Then I clean the contact pads on the keyboard with Isopropyl alcohol and after everything is dry, put it back together. I've got one of those repair kits for the conductive buttons on the back of the keypad, but I've never had to use it.
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One man's Magic is another man's Engineering. |
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SparkChaser
BURY BECK
Premium
join:2000-06-06
Downingtown, PA
·Verizon FIOS
·Comcast
| reply to sporkme
Do not use tuner lube/cleaner for the reason Tursiops_G  said. (they still make that stuff  )
That high test isopropyl should do the trick. I've never had the need for the repair kit, either. The musical KB takes a pounding and I've always been able to restore it as mentioned previously. |
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sporkme
drop the crantini and move it, sister
Premium,MVM
join:2000-07-01
Morristown, NJ | reply to sporkme
Thanks all... I'll clean the keypad assembly as described and go for the isopropyl on the board and see what happens... |
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sporkme
drop the crantini and move it, sister
Premium,MVM
join:2000-07-01
Morristown, NJ
·Optimum Online
| All went well. My buttons now work with little force.
I did kind of screw up though... On the PCB, the contacts are graphite(?) as well rather than just copper traces. I started "cleaning" that as well and noted that the q-tip was turning black. I came quite close to cleaning these contacts right off the board. |
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Blackbird
Built for Speed
Premium
join:2005-01-14
Fort Wayne, IN
 ·Verizon Online DSL
| said by sporkme :... On the PCB, the contacts are graphite(?) as well rather than just copper traces. I started "cleaning" that as well and noted that the q-tip was turning black. I came quite close to cleaning these contacts right off the board. The carboned contacts give a corrosion/oxidation-free, fairly low-resistance contact surface and are cheap to produce. But when cleaning, you do have to be careful not to "scrub" off the black material, especially on the board where there's usually not as thick a layer. Even if the carbon comes off, you still should get a good contact with the metal pad beneath, but that switch will become more susceptible to more rapid oxidation effects thereafter.
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If God wanted us to work with electrons, He'd make them big enough to see... |
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