Rubber keypad contact repair options...

Discussion in 'General Electronics Chat' started by creakndale, Dec 4, 2010.

  1. creakndale

    Thread Starter Active Member

    Mar 13, 2009
    I have a 25 year old obsolete alarm system with keypads that are about worn out. I've taken one of the keypads apart and the problem is a lack of conductive material on the back of the rubber membrane due to lots of use. In researching possible solutions, I found 4 that seem viable.

    1) Use MG Chemicals 8339 Rubber Keypad Repair Kit.
    2) Use Barclay Perma-Pad or similar button replacements.
    3) Use Chemtronics CW2605 Rubber Keypad Repair Kit.
    4) Purchase a used keypad from eBay.

    Has anybody had any experience with the first 3 products and obtained long term success? Or possibly some other repair option?

  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Pencil eraser (white kind) on the copper pads lightly.

    Isopropyl alcohol 90% on the pads.

    This is if you can measure resistance on the black part of the bottom of the plastic flex-buttons. If that isn't conducting, you'll need to re-apply it.
  3. awright

    Well-Known Member

    Jul 5, 2006
    I don't know about rubber keypads specifically, but alcohol is a no-no on rubber in general. It tends to harden the rubber. Back in the day of the typewriter and daisy wheel and dot-matrix printers, users were cautioned not to use alcohol to clean the rubber plattens but to use a solvent with the trade name Fedron, instead. It was claimed to "condition" the rubber. Of course, the plattens had no conductivity to be concerned with.

    I've used a freon solvent to clean calculator rubber keypads successfully in the distant past, but I don't think they are available currently due to the greenhouse gas issue. One small can lasted decades until the plastic cap deteriorated with age or solvent attack, cracked, and released the remaining freon unbeknownst to me.

    I'd research further before using alcohol on rubber keypads.

  4. debe

    Well-Known Member

    Sep 21, 2010
    Conductive silver based paint for repairing PCBs or car rear demister repair is what i painted on the faulty rubber pads on my fishing depth sounder. Its still working.
  5. creakndale

    Thread Starter Active Member

    Mar 13, 2009
    I did clean the contact areas on the PC board and the conductive membrane buttons with 91% Isopropyl Alcohol and Q-tips with the understanding that the Alcohol might drawing out the oils in the rubber.

    The measured resistance of the good membrane buttons appears to be 100 to 150 ohms. It's more difficult to get readings on the bad buttons since the conductive material is worn away in some areas but intact in others. I was able to measure between 300 to 1K ohms. It does work better after the cleaning.

    The easiest fix is to not use those particular 4 digits for the alarm code and reprogram the alarm to use the remaining good digits. However, I'm looking for a permanent fix since I plan to sell this house in the next couple of years.

    Thanks for all the suggestions. I'm probably going to try the MG Chemicals 8339 Rubber Keypad Kit. I also have an old RCA TV remote that needs rejuvenated.