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HP41C strange display behaviour - Printable Version

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HP41C strange display behaviour - Alberto Fenini - 01-21-2010

Hi everybody,
I have received a second HP41C unit, and I did some repair on it.
One of the internal battery contacts was ruined and I have restored it with a thin metalic film soldered over the original contact.
It worked out, since now the unit is turning on.
However, the display is not able to light up all the segments, making it unreadble and unusable.
I have warmed and re-soldered the display contacts, both on the keyboard side and on the display back, but nothing.
For example the ALPHA label is not showing up on the display, even if the unit is in alpha mode.
What could I check without destroying the machine ?
Thanks for help, take care Alberto

Re: HP41C strange display behaviour - John Robinson - 01-21-2010

Hi Alberto, it is possible to disassemble the display itself, but first you would nened to desolder it and remove it from the calc. There is a black metal spring "clip" along the top and bottom of the display. By removing that gently, the display should come apart into four pieces, the circuit board, the glass "display" and two ribber "zebra" connectors. You should clean the contacts on teh circuit board, glass display and clean the zebra connectors all with a good electronics cleaner, say an electolube product, then reassemble gently, and resolder it back it.