HP 42 S flaking out


Recently my 42S started “flaking out”. 1) The self test says okay but periodically instead of going to sleep it starts beeping steadily and then it resets the machine 2)after a delay in keystrokes I think that the decimal point or some series of key strokes with the decimal point also imitates a machine reset. Any ideas?

Perhaps some cleaning of contacts would work if I could open it


Are the batteries fresh? Are you able to check the voltage of the 3 battery stack during operation? Anything below 3.8 volts and you will have trouble, maybe sooner. I have found the battery annunciator to not be a reliable indicator of battery condition.

A liquid spill in the keyboard may cause this behavior as well. Coffee, cola and others would certainly make a mess of things.


The batteries went dead, and I didn't replace them even close to right away. It was probably 6 months later that I decided to replace the batteries. Now, after replacing the batteries, I turn it on and get all the pixels in the display are 'on'. Any buttons I press, results in a beep. I've tried the self test - beep. I've tried the reset - beep.

Is it a lost cause?



The beep means at least the processor is running but perhaps the ROM fails checksum?

Anybody know for sure?

Could it be a bad battery? I would check them if you can.



have you already tried to briefly (a lot briefly) shorten the batteries' terminals? Get a little piece of conductive metal, preferably a wire OR a thin paper clip. Carefully remove the batteries' cap. WITH THE BATTERIES INSIDE THEIR COMPARTMENT, briefly (a lot briefly) shorten the batteries' terminals. Keeping the batteries there will NOT ALLOW voltage to go upper than the 4.5 Volts. Place the cap back.

Whatever happens, let us know.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP-67's Flag 3 to HP-41/42 Equivalent Matt Agajanian 2 909 03-29-2012, 06:29 AM
Last Post: Dieter
  HP 82240B. Infra red printer for HP 42---HP 50g Stuart Sprott 20 3,407 04-29-2010, 01:52 PM
Last Post: Vieira, Luiz C. (Brazil)
  HP41/42 Unit Conversion Egan Ford 36 5,629 03-30-2009, 11:30 AM
Last Post: Martin Pinckney
  Need help transitioning from 41/42 to 33/35 Bill Colisch 2 773 10-13-2007, 12:27 PM
Last Post: Bill Colisch
  Microchallenge 41/42: nr of digits Werner 3 953 09-14-2007, 04:35 PM
Last Post: Howard Owen
  HP-97 and HP-42 Gerry Schultz 4 1,131 06-06-2007, 10:54 AM
Last Post: Jim Creybohm
  Key Sounds in a 42 Ron 5 1,277 01-03-2007, 10:07 AM
Last Post: Ron
  42.4242424242 Gerson W. Barbosa 9 1,692 09-18-2006, 07:09 PM
Last Post: Gerson W. Barbosa
  Emu48 1.42 and WINE - It Works! Howard Owen 0 437 09-02-2006, 10:21 PM
Last Post: Howard Owen
  HP42S program (Survey-Quik Calc 42) K Kelley 2 733 08-26-2006, 10:48 PM
Last Post: Todd

Forum Jump: