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HP Forum Archive 08

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HP-42s keyboard error
Message #1 Posted by SV on 13 June 2002, 8:09 p.m.

Hello:

I have an HP-42s that gives the following keyboard error in the self test: "KBD 02501", and then it says "FAIL 00020". The keys are very sticky due to something being spilled on it. (I am not the original owner). Can something be done about this? Is there a way to take apart the calculator to service the keyboard and clean it up of the dried up soda that probably caused all this?!?!?!

      
Re: HP-42s keyboard error
Message #2 Posted by Randy Sloyer on 13 June 2002, 8:52 p.m.,
in response to message #1 by SV

I would agree that the spill is most likely the problem. A "stuck" key would cause that error.

While you could disassemble the unit, I don't think that would be the best first course of action. I have read here several times (not personal experience) that you can clean the unit in a ultrasonic cleaner with distilled water (more than one cycle) then dry completely at 120 degrees F max for several days. Do this WITHOUT the batteries in place. This should remove the residual sugar and sticky residue. You must completly dry the unit before re-installing the batterys and powering on.

There are several threads here and the forum archives on trying to repair the keyboards on the pioneers and none of them have had good results.

Don't consider it dead yet.... and don't do anything drastic.... yet.

            
Re: HP-42s keyboard error
Message #3 Posted by Ron Ross on 13 June 2002, 9:11 p.m.,
in response to message #2 by Randy Sloyer

If it is a total loss, sell it (and I would want to buy it!!), to try a ROM switch with a 17B to make a 17B into a 42s sans keyboard.

That is probably your best course of action since the keypad is the most delicate and hard to replace part.

                  
Re: HP-42s keyboard error
Message #4 Posted by David Smith on 14 June 2002, 4:37 p.m.,
in response to message #3 by Ron Ross

Unless you have some VERY specialized equipment you cannot change the "ROM" in these machines. It is all located on the CPU chip which is a "TAB" package - Tape Automated Bonding - Basically a bare silicon chip attached to a small flex circuit. Consider it utterly impossible to remove and reattach.

                        
Re: HP-42s keyboard error
Message #5 Posted by Randy Sloyer on 14 June 2002, 10:00 p.m.,
in response to message #4 by David Smith

Dave:

Were you able to tell from the error message that the ROM is bad? I looked thru all my 42S stuff and came up empty.

Just curious.

                  
Re: HP-42s keyboard error -- Fixes?
Message #6 Posted by Paul Brogger on 14 June 2002, 5:19 p.m.,
in response to message #3 by Ron Ross

I've done this twice, but it's not a ROM switch, per se -- it's a PCB switch.

To take a Pioneer apart, see & read all at:

MoHPC Repairs & Batteries Pioneer Repairs

MoHPC Articles Forum -- #199: Increasing HP-42s Memory to 32K

(No guarantees, of course . . . ) Be careful, good luck, and email or post any questions or concerns you have.

To take apart and rebuild a keyboard sandwich, see another message in this Forum.

Again, good luck!

                        
Re: HP-42s keyboard error - my mistake!
Message #7 Posted by SV on 14 June 2002, 10:10 p.m.,
in response to message #6 by Paul Brogger

Hello:

I've made a mistake in the self-test. After the screen says "KBD", I hit the "+" key mistakenly thinking that the 42 would run a keyboard test. That is when it gave me the error message. I did not realize that you had to push all the keys starting in the top left and proceeding to the bottom right. Once I did this, I got the "OK" message!

The keys are very sticky though, but at least this 42 is still functional, albeit a bit cumbersome! Now I need some documenatation (manuals) !!

Thanks again for your responses!

                              
Re: HP-42s keyboard error - my mistake!
Message #8 Posted by Ellis Easley on 15 June 2002, 7:38 a.m.,
in response to message #7 by SV

The 42S users guide and an applications manual are on the MOHPC CD-ROMs. The applications manual was also still available as a reprint from HP (at least it was recently) for $38 which is more than the CDs.


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