Hard to use Woodstock keyboard keys


Hello HP collectors fellows,

I've bought a pretty nice HP29C with a mentioned problem about the keyboard: keys on the lower left corner are hard or even impossible to use.

I was tempted to open it and discovered that the keyboard is like a sandwich of two boards with plastic axles melted that prevent from any dismounting of the sandwich.

Can anyone direct me to a method to recover correct contact behavior and get this 29C back to work?


(My site, just in case...)


When you say 'hard to use' do you mean that they can't be pressed, or that you can press them and they feel normal, but they have no effect?


When you say 'hard to use' do you mean that they can't be pressed, or that you can press them and they feel normal, but they have no effect?

The keys can be pressed but produce no effect


Follow Pauls post. I use a small wire brush made from three wire brush bristles twisted together in a pin vise or hobby knife holder and trimmed even.


I'm not sure if your keyboard has the same construction but I used the following method with succes in my 41CV that had a faulty 'ON' key.
The keyboard consists of little dome shaped metal springs that provide electrical contact with a pad on the PCB once you press it. And they also provide the positive tactile click that we al like so much. You don't have acces to the springs because of the moulded plastic studs you mentioned. You can however see the PCB pads on the bottom side of the PCB since they're through-hole metalized. You can even see the spring moving once you press a button if you peek through these holes. I used a needle to insert a tiny drop of contact cleaning fluid through these holes. After pressing the key a couple of times to make the fluid do it's work, the keys functioned like new again.
Don't be tempted to use the spray-can of cleaning fluid directly on the calc,since it will penetrate al places where you don't want it. Just spray some in a little cup and use a needle to put a tiny droplet into each hole on the PCB that has a faulty key behind it.

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