|Re: Knocking on HP-41s back door :-)|
Message #2 Posted by Diego Diaz on 5 June 2010, 5:22 p.m.,
in response to message #1 by Juergen Rodenkirchen
It seems a typical case of weak contacts.
There are several points inside HP-41 that may lead to such a behaviour.
- Battery <> I/O block, (both coconut and halfnut), often caused by battery leakage corrosion, or mechanical damage in the I/O block battery terminals/or battery compartment springs.
- I/O Block <> Keyboard (both coconut and halfnut), more likely caused by broken post in the upper screws, or battery leakage corrosion.
- CPU board <> Keyboard (only coconut -AKA fullnut-), caused by broken post in the lower screws, or damaged "zebra" strip (be it polymer or metallic)
- LCD <> LCD control board (coconut, very unlikely on halfnuts) again damaged "zebra" strips are the more common cause.
If your I/O block is clean and shows no traces of corrosion, my advice is to take your HP-41 apart and check for broken/cracked screw post(s).
Hope this helps.