ACT available

[Frido Bohn]

Found some quiet minutes yesterday to install Bernhard's ACT in my venerable HP-25. The desoldering procedure was really wearisome. Generally all went well but there was one pin that refused perseveringly the removal of tin and took about 50% of the total time to remove the original chip. After cleaning up the pin holes from remains of tin and probing the openings with a needle of sufficient gauge I managed to insert the socket strips and soldered them on the board. The new ACT could be plugged into the socket with a bit of forth and back movement. I reassembled the two boards and checked whether all was working properly. And yes, upon switching it on the calculator gave notice with a personal greeting - thank you Bernhard for this little extra!

However, as I reassembled the calculator completely, the display either didn't work at all or showed only random signals. First I was appaled and worried that somethings went really wrong but I noticed soon that the display changed when I pressed on the keyboard. I suspected a mechanical cause, and indeed, after opening, I realized that the new ACT had some play within the socket strip. My workaround was to put some foam plastic on the new ACT, so the circuit board of the keyboard would excert some pressure on the chip when both boards were reassembled.
This strategy works well so far and I am enjoying now the full funcionality of an HP-25E.

To prevent contact issues of the new ACT with the socket I would recommend to install the chip with the socket strips attached onto the board first and solder the socket pins on the keyboard with this kind of in situ technique.
I don't know if this is a good idea and I am sure that it is due to my inexperience that things became a little awkward.

Anyway, the new ATC with its extended features is really a marvelous piece and moves the good old HP-25 in an area where no one could have imagined.

Thank you again, Bernhard!
Frido