HP 25 malfunctioning keys


Good morning everyone,

I recently bought an HP 25 in very good condition -- excepted that two keys, the [4] and [5], require several presses to get to work. Sometimes I need to press strongly two or three times, sometimes up to ten times before a '4' or a '5' appears. The typical vintage HP "click" feeling is otherwise fine on all keys, including these two ones.

Is there an easy method (maybe similar to the one for the new HP 49g+) to smooth these two keys? Or is is some dust inside?

Thanks a lot.


Hi Emmanuel.

I had this same problem with my 25 (except w/ 4&6), and I over came it by opening the calculator and running a little bit of rubbing alcohol and cloth under the keyboard metal "bubbles". I used a toothpick (as per someone else's post in the museum) with emery cloth to finish.

Works great!



The HP25 keyboards are different than the classics... no key strips to clean under. Most styles of the HP25 keyboard do have a hole in the circuit board under each key. You can clean the keys with a small brush made out of three stands of wire brush bristles chucked in a pin vise, twisted together, and trimmed square. Dip in 91% isopropyl alcohol, place a drop of alcohol in the offending hole, and lightly "scritch" away in the hole.

If your keyboard does not have the holes, you can carefully drill an access hole with a pin drill. Avoid drilling into the circuit traces on the back of the keyboard. Also avoid letting drill shavings into the hole.


It's not a big issue yet, but the number "2" is starting to have similar symptoms on my hp-29c. It sometimes requires several presses now to register a "2".

I'm the original owner of the machine which I've had I think since '77 or '78. (I guess 25 years of faithful service is pretty darned good so I can't really complain..)


Many HP-29C machines have keyboards without the holes. Even worse the circuit board is black and opaque... you cannot see through it to avoid drilling an access hole into a circuit board conductor.


Thank you, it worked perfectly.

Possibly Related Threads...
Thread Author Replies Views Last Post
  Broken keys on HP Prime? Tarcisi C 0 696 12-10-2013, 05:59 PM
Last Post: Tarcisi C
  Strange HP 25 Problem (Repair) Onur Ilkorur 5 1,486 12-06-2013, 05:13 PM
Last Post: Onur Ilkorur
  HP 50g switching two keys in the user keyboard Sean Freeman 9 2,062 12-05-2013, 11:44 AM
Last Post: Mark Puscas
  HP-25 Wayne Selway 1 654 11-22-2013, 12:58 PM
Last Post: Michael de Estrada
  [HP-Prime] off-center [0], ... [9] num keys CompSystems 1 689 10-18-2013, 10:44 PM
Last Post: Han
  HP Prime - Home and CAS keys BruceH 0 490 10-15-2013, 07:19 PM
Last Post: BruceH
  Interesting Base Conversions - Porting a 1975 HP 25 Program to the HP 35S Eddie W. Shore 1 707 10-13-2013, 07:49 PM
Last Post: BruceH
  HP Prime Tip: Setting Up User Keys Eddie W. Shore 2 841 09-27-2013, 09:53 PM
Last Post: Eddie W. Shore
  [HP-Prime] Lack of user soft keys Andy B (Australia) 1 603 08-17-2013, 11:00 AM
Last Post: Tim Wessman
  HP-25/25C Potential Matt Agajanian 14 2,362 07-17-2013, 02:57 AM
Last Post: Matt Agajanian

Forum Jump: