Clean, fix or replace pushbutton switches

Discussion in 'The Projects Forum' started by darenw5, Jun 18, 2009.

  1. darenw5

    Thread Starter Active Member

    Feb 2, 2008
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    I've taken apart my music keyboard/synth to try to fix some balky buttons. Cleaned out dust, etc. This is a pricey professional keyboard, and it used to work great (for a 1990's instrument) but due to aging and bumpy transportation some buttons aren't working reliably, taking several presses or extra force to function.

    Are there any clever tricks to restore youth and proper functioning to these switches? I'd like to try something else before searching catologs to order replacments. Here is a photo of one switch: [​IMG]
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
    758
    57
    Hi.
    Those switches are sealed, contain a snap disc prone to lose reliability and I would suggest you replace them; they are inexpensive. Search as 'tact switches'

    Just make sure the stem length is exactly the same or the buttons on top of them may keep them pressed or not reach them.

    Miguel
     
  3. loosewire

    AAC Fanatic!

    Apr 25, 2008
    1,584
    435
    Another Gemini,do you think tuner cleaner will slid in around
    the pushbuttons,just a dap.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You might try some spray electronics parts cleaner. Sometimes gunk gets down in there, or the contacts get corroded. Good luck getting it out; unless you tip the thing completely upside down there's no real exit path.

    That looks like a standard tactile switch.

    Here's one type:
    http://www.westfloridacomponents.com/SW084/Tact Switch 15V 6mm Panasonic EVQPAG04M.html
    That's a DIP package. I don't see dip leads on yours though; not sure if it's the lighting or that yours have radial leads.

    Omron makes a bunch of tactile switches. Here's their online catalog:
    http://www.ecb-web.co.jp/ecb_en/products/search/index.php?l=sw&s=21
    Yours might be like the B3F-6000 series; radial leads. Looks like your plunger is the flat 5mm type. I don't see a ground lead, unless it's hidden on the other side of the switch plunger.

    That narrows it down to B3F-6020 or B3F-6022 depending upon how much force you want to use to actuate the switch.

    Digikey carries both of those; around $0.36/ea if you're just buying a few.
    B3F-6020: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SW796-ND
    B3F-6022: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SW264CT-ND
    Better double-check carefully before ordering any though. My size guesstimations may be wrong.

    Here's another by E-switch; even the color of the plunger is similar to what you have:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=EG4378CT-ND


    Oh, for really small orders, Digikey will ship US Mail 1st Class. That'll save you lots on shipping.
     
    Last edited: Jun 18, 2009
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    High quality (but reasonably priced) switches designed for low signal levels have gold-plated contacts that do not corrode.

    Poor quality switches designed for high currents have silver plated contacts that turn black with corrosion and do not pass low level signals anymore.
     
  6. darenw5

    Thread Starter Active Member

    Feb 2, 2008
    45
    0
    Thanks for the answers. These switches are totally sealed, so tuner cleaner would be useless. This looks like a replacement job. At least they're cheap, and the supplier in Florida might be cheap shipping, as I live in Florida.

    Argh, I was hoping for a lazy-compatible solution!
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Darenw5,
    The more I looked at your photo, the more the tactile switch looked like the radial lead package. If that's the case, the DIP package tactile switch that westfloridacomponents has won't fit.

    I didn't know you were in Orlando. You might check out Skycraft Surplus; they're on Fairbanks just east of the I-4 freeway. They have a huge selection of components and parts; it's well worth going there just to get a feel for the place - even if they don't have the exact part you need.

    However, keep in mind that their stock generally comes from manufacturers who are either just getting rid of excess inventory, or who have gone out of business. There's no telling how long some of their stuff has been sitting around - and if you happen to get tactile switches with the silver-plated pop domes inside that have corroded with age, you'll be right back where you started.

    I strongly suggest that you use only new components to repair your keyboard, not "new old stock". Some of westfloridacomponents' stock is "new old stock". Digikey only sells new stock.

    As I mentioned above, I think that the B3F-6020 or B3F-6022 look mighty close to what you have, but you'll need to take some measurements to be certain.
    Here's the datasheet for those switches:
    http://www.omron.com/ecb/products/pdf/en-b3f.pdf
    Scroll to the bottom of page 14 for the physical dimensions.

    As I mentioned before, Digikey will ship 1st class USPS, which will save you a lot on shipping costs vs UPS or FedEx.
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    They're not sealed, spray cleaner solvent will go right through with no problems. However it won't always save your buttons, I recently replaced 30 buttons on an old Roland D20 keyboard here with the same problem, the cleaner helped a bit but they were internally corroded. That was also on a single sided PCB, it only takes a minute a button to replace each button and mine were 4 pin.

    Yours should be quicker, being 2 pin. Try heating the 2 pins at once with your soldering iron if you can to speed up the replacement.
     
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