33E with bad keyboard



#4

I noticed a non functioning HP 33E on eBay today and it is going for over $50, are these really worth anything? I have two of them with keyboards that are not making reliable contact with the keys. Can they be fixed?

Chris W

Bring Back the HP 15C


#5

Hi, Chris;

I remember having a "bad time" with an HP29C in the 80's. It had a bad [ENTER] key that sometimes worked, and most of the times didn't. I sadly confirmed that the keyboard was faulty in a way I was able to repair at that time. Today I'd be able to, I guess.

Now with the Spices: there are two main types of Spices, being them solderless (sandwich-type assemble) or soldered with respect to the IC's. The solderless units have a flex circuit "board" that is folded over itself and goes from the IC's pads and connections to the keyboard. In fact, the flex circuit itself composes all key contacts. Under each key there's a dome molded in the flex board, sort of a sphere cap with a recesed center. Inside this "inversed" surface is located the contact pad. BUT there is also a copper trail that connects each contact pad with all others in the same alignment (matrix-like arrangement) and them to the respective pin in the main processor. The soldered-type units have metal caps under each key.

This "plastic bubble like" keyboard assy used in the solderless Spices is the same one I found in that HP29C. The problem is that the copper trail and/or the plastic cap may crack (?) and no contact is made when the key is pressed. That's what happened with the HP29C. And I guess it happens with other models as well.

The HP48 (and others, like Pioneers) uses the same plastic caps molded in one flex circuit, but they don't have copper trails. Instead, the caps have a single conductive "island" inside them that is pressed over a fork-like contact pair in the flex circuit counterpart. It is a lot more safe and reliable.

I hope this gives you an idea. If you have Spices, it's always a good chance to keep a "working spare" somewhere in the house.

Success! and Cheers.

Luiz (Brazil)

#6

Hi Chris,
Yes the units are of value to anyone who has one, who is actually using it instead of storing it as a "Colletors item". Mine is in near mint condition and I use it daily as my primary unit for number crunching.
Best of luck
Paul M


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