General > General Technical Chat

got a suggestion about restoring a membrane keypad?

(1/4) > >>

slburris:
Hi,

I'm working on a project to restore a WaveTek 275 Arbitrary Function Generator.
It works, except the front panel doesn't respond very well to keypresses.  If you
keep pressing, eventually a button will respond.  Some buttons are worse than others.

Being lazy, I tried the cheezy way to clean this -- I sprayed some alcohol under the membrane,
hoping to flush out any dirt.  I didn't think it would work, and it didn't :-(

So I've taken the front panel apart and peeled back about half of the membrane.
Looks like the "keys" are copper pads which touch a wire matrix when pressed.  From
poking around with my DMM, it looks like the contact problem is happening between
the pads and the wire which runs underneath.

So my thought is to burnish the copper pads, probably with a pencil eraser, and
lightly run over the wires with an x-acto knife to clean off any oxidation.  Since this
keypad is probably unobtainium at this point, I was wondering if someone had experience
doing a restoration like this and had any better suggestions?

Scott

saturation:
I would avoid a knife, if I accidentally cut something in unobtanium, it would be hard to get a substitute unless I buy another damaged device for parts since that keyboard is custom made.

I've used erasers too with great success.  But to avoid torsion forces, buy a cheap electric eraser, it could do all you want with the least work, and if it doesn't work it won't break the bank.

A Staedtler Electric Eraser, is sold in the US between $5-10 and the eraser refills is a box of 20-30 heads for $3.  The Sakura Electric Eraser one is Japanese original and costs $40!  They are 2x AAA powered.





Video:



http://www.artistsupplysource.com/product.php?productid=25326

The reason its cheap is just its an electric motor that spins an eraser head. 

Mechatrommer:

--- Quote from: slburris on July 02, 2010, 04:47:11 pm ---Looks like the "keys" are copper pads which touch a wire matrix when pressed.  From
poking around with my DMM, it looks like the contact problem is happening between
the pads and the wire which runs underneath.

--- End quote ---

which part are you trying to erase? the top part of copper pad? or the underneath part where the pad and wire mesh contacting? the contact is underneath... u must have access to those area i think. erasing the top part wont do any good. thats the way i see it from the picture u showed.

slburris:
I'm erasing the copper pad underneath.  I'm trying to just peel
back half of the switches to get access to the wires and pads.
That might not be clear from the picture.

Once the first half is done, I'll carefully peel back the second half
and repeat.

Scott

NiHaoMike:
If it couldn't be fixed, solder in small pushbuttons. I once fixed a cordless phone with a bad power button by soldering a pushbutton from a broken VCR across the contacts, then carefully cutting the rubber button so it fits.

Navigation

[0] Message Index

[#] Next page