HP-25 Repair Tiips Needed.
#1

I’m looking for advice in repairing a HP-25. The PCB is covered with blue residue. What is the best way to clean the PCB and surrounding parts? I could use some tips on how to remove the circuit board that connects to the keys. I’m concerned about prying the board free, as it might damage the board. Thanks - Tony

#2

A repair tip would also be appreciated. Thanks - Tony

#3

The PCB comes away from the keyboard assembly easily enough, as does the LED panel from the PCB. I'd use Isopropanol alcohol and q-tips (cotton buds) or dilute bleach (then neutralise with bicarb) If you use the bleach approach use a hairdryer to dry. DO NOT get the LED panel wet. You cannot separate the keyboard from the shell easily, if thats where the verdigris is then come back for more advice.

#4

Thanks Dave - I would like to separate the keyboard from the shell. The keys have a very stiff (little action) feel to them and the "4" key displays a 6. I wanted to see if there was anything I could clean up. Any ideas on how to tackle this one? Thanks - Tony

#5

I've never needed to separate keyboard from shell for verdigris removal; I might try agitating for a few minutes in dilute bleach (pressing keys while doing this) then bicarb then wash with clean water for a *long* time then dry. What I think I'm saying is that *almost* anything is preferable to taking the keyboard apart! It is possible, the chances of wrecking the keyboard are large. Remove the heat stakes - use a sharp knife to remove the 'overflow' of plastic (i.e. NOT the actual stake, just the excess stuff that is keeping the board against the stake). Wash as described. Reassemble and while holding the board onto the stakes, use a soldering iron on the centre of the stake to spread it. Be sure that the power and prog-run switch are assembled before you do this, there are few second chances. I additionally use a piece of foam rubber to hold the battery compartment against the keyboard PCB as heat stakes never fully reassemble! Good Luck, you *will* need it!



Possibly Related Threads…
Thread Author Replies Views Last Post
  Strange HP 25 Problem (Repair) Onur Ilkorur 5 2,794 12-06-2013, 05:13 PM
Last Post: Onur Ilkorur
  HP-25 Wayne Selway 1 1,209 11-22-2013, 12:58 PM
Last Post: Michael de Estrada
  Interesting Base Conversions - Porting a 1975 HP 25 Program to the HP 35S Eddie W. Shore 1 1,313 10-13-2013, 07:49 PM
Last Post: BruceH
  HP-25/25C Potential Matt Agajanian 14 4,096 07-17-2013, 02:57 AM
Last Post: Matt Agajanian
  [OT?]Orthography corrector needed. Diego Diaz 8 2,532 06-22-2013, 04:31 PM
Last Post: Andrew Nikitin
  Recharging original batteries in HP 45, 65 and 25 Michae Altmann 1 1,212 03-05-2013, 12:21 AM
Last Post: DavidShenk
  HP-50g How to store many equations - help needed Timo Labrenz 5 2,028 03-03-2013, 12:22 PM
Last Post: Timo Labrenz
  HP-25 keyboard Brad Barton 5 1,857 02-16-2013, 09:59 PM
Last Post: Brad Barton
  Disaster: help for a couple of HP97 needed! Jose Gonzalez Divasson 10 2,898 01-21-2013, 04:45 PM
Last Post: aurelio
  HP41 emulator for HP48sx - keyboard overlay needed Doug (NYC) 3 1,568 12-31-2012, 03:11 PM
Last Post: Allen

Forum Jump: