Key bounce problems with the HP 15c LE

[Michael de Estrada]

I've been experiencing really bad key bounce problems with my HP 15c LE calculators. I have two of them that I've been using regularly that came from totally different manufacturing batches, and they both do this constantly. It does not seem to be confined to any particular keys or section of the keyboard, and I'm at wits end with them. I'm wondering if this is some mechanical design problem or perhaps just a bad internal keytime choice in the firmware. I know that it is possible to increase the keytime in my HP 50g to avoid key bounce, but AFAIK there is no way to change this in the HP 15c LE w/o a firmware update, which is very unlikely to ever take place. It's really a shame, because I bought these calculators to save wear and tear on my original Voyager HP 15c, but they are practically useless with this behavior.

[Mark Hardman]

(01-04-2014 05:17 PM)Michael de Estrada Wrote:  I'm wondering if this is some mechanical design problem or perhaps just a bad internal keytime choice in the firmware.

The poor manufacturing quality of the HP15C LE keyboard is well documented in the original forums.

Try doing a Googe search on: "hp15c le keyboard site:www.hpmuseum.org".

M. Joury gathered statistics in the following threads:

HP15C LE Keyboard Survey
HP 15C LE Keyboard Survey Redux
HP15C LE Keyboard Survey Results

He found a non-scientific failure rate of 11.7%.

Sorry, but your HP15C LEs are now "collectible display pieces."

Mark Hardman

[Michael de Estrada]

Hi Mark,

The problem I'm having is a totally different issue than what you have posted. My problem is not that the keys don't register, but rather that they repeat (double entry) when pressed.

Michael

[W_Max]

Well... This is the beginning. After some while, bouncing keys become faulty as a result of oxidizing of poorly made keyboard contact pads. I wonder - why 15LE worth so much, as it quality is similar to 35s (or even worse). May be pads cleaning can resolve problem, but I think this is very difficult task...

[Ail]

I also have a 15C LE that double registers at seemingly random keys. My 12C 30th Anniversary does not have this problem even though the keyboard feels exactly the same. For now my 15C LE is sitting in a drawer somewhere...

[d b]

The result of an un-scientific and un-representative sample by yours truly suggests that the lower the serial number, the less likely a 15CLE is to have keyboard problems. This is usually due to tiny white poo-poos in the domes which got more prevalent later in the run. Cleaning can't hurt but getting everything out has been practically impossible. I don't know whether blowing it out dry or using something with a silicon residue is best. If anyone can do it you can. Good luck old buddy.

[Thomas Radtke]

(01-05-2014 12:12 AM)W_Max Wrote:  [...] poorly made keyboard contact pads.

What's the problem with them?

[Marcio]

(01-04-2014 10:41 PM)Michael de Estrada Wrote:  Hi Mark,

The problem I'm having is a totally different issue than what you have posted. My problem is not that the keys don't register, but rather that they repeat (double entry) when pressed.

Michael

Sir Michael,

Did you ever fix the keys of your 15C LE? Did you try shorting the terminals together, if that is possible or make any sense at all.

I am asking because I bought a second-hand 12C that apparently uses the same hardware as the 15C LE and keys have the same problem as you have described. Also, the f and g keys are not as firm as the other keys, just like shown in this video with a 15C LE..

Or maybe I should just return it.

Thank you.

[Thomas Radtke]

Marcio, your 12C might have a similar emulator as the 15C LE that probably get the keyboard timeout wrong.

If I'm not mistaken, HP had a similar problem with the 49G+.

[Marcio]

Thank you Thomas for your input.

I have been playing with it quite a bit (I'm a power user = I use them a lot) and it seems the double-registering problem is fading out as I press the keys.

The f and g keys being loose doesn't bother me that much though.

On the plus side, yes, the machine is amazingly fast. It computes \(sin(a)\rightarrow y\) and \(cos(a)\rightarrow x\) using Valentin's tried and tricky trigonometrics in a blink of an eye.