Beep problem hp 41 repair



#5

Hi, I read through all the repair messages that this very knowledgable group has assembled but I can't find anything on this recent problem:
I bought a couple of HP 41 and they seemed to do fine. Curious as I am I opened them, also to clean some corrosion. However when I put them back together, they either have a little high pitch beep right when I put in the batteries, or when I press the on button. One works afterwards fine, the other one shows funny characters and does not. Does anyone has any tips or ideas what the source of the problem is? How I can fix it? Thanks a mil in advance.
Cheers


#6

Hi, the short beep after inserting batts after a while

seems to be normal for some older units.

If you hear a beep after every keystroke,

this indicates that the OUT or Tone register

hasn't been reset properly.

Just perform a BEEP, then it should disappear.

For the machine(s) which show weird stuff on the display:

Usually this means a bad contct between the CPU board

and the keyboard pcd, and/or the contact between

the keyboard pcb and the battery contact block.

Be sure not to fasten the screws to tightly,

as the posts tend to break.

HTH

Raymond


#7

Raymond, Thanks for your reply, it must have scared at least one of the HP-41's - it stopped beeping!

I checked the other one for contact between cpu and keyboard and - Voila - there was corrosion on the connector (i think it is called the zebra connector, right?) I tried to clean and fix it, yet to no avail. Got once a steady "Memory Lost" display with no keys working. Than I turned the zebra around to see if that changes anything, nope. I read in the 'Repair of a HP41 CX" article how the cpu can be hardwired to the keyboard, it just sounds like a lot of work...
Any idea how to clean/repair the zebra?

On a different note: One of the beeping ones seems to have been subject to a speed up and I wonder if the capacitor is broken (it looks pretty bad...). It is on the left side of the board (facing down, display on top side), where there is a second lengthy, slivery capacitor mounted on top of a first similar looking one. That second one is connected with a blue capacitor which is with a wire soldered to a spot on the top side of the board. Can I just remove the two extra capacitors and the wire?

Thanks so much for your help to a repair newbie...

Peter

#8

I just found some PPC article with respect to speed up and so I did take out the extra 2 capacitors with the cord. It then had the beeping problem that I resolved following your sage advice of "BEEP". it now works fine.

Thanks a lot yet I'm sure more questions will arise once I try to revive the last of the batch, maybe I do do the hardwiring of the cpu-board... any other/better ideas, please send them forward!

Cheers


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