HP-41 oddity typing alpha letters

[Monte Dalrymple]

(05-06-2020 10:21 PM)Gene Wrote:  No spell check rom. ;-)

Here are some other examples:

ABCDEF then G changes the F to an N. Continuing with HIJK does not change the N. The F is gone. Interestingly, FEDCBA then G changes the A to an I.

ABCDEG then H changes the G to an O (oh not zero). Continuing with IJKL does not change the O. The G is gone.

ABCDEQ then R changes the Q to a Y. But typing an S changes the Y back to a Q.

ABCDEU then V changes the U to a backward C (the close bracket). Pressing W changes it back to a U.

FGHIJK then L does not change the K.

But...

QRSTUV then W changes the V to the UP ARROW. Further letters to not return the V.

CHLORV then C puts the UP ARROW. IF you type H or L or O or R instead of that C, you still get the UP ARROW.

DIMPSW then X replaces the W with the underscore character. Any character other than the W does the same thing.

YUQNFR then C replaces the R with Z.

Hmm...

XEQ ALPHA SIZE ALPHA then filling in the three blanks with 030 ... when the first 0 is pressed it shows as an 8 then when 3 is pressed is changes back to a zero.

XEQ ALPHA PRO ... trying to do a PROMPT ... as soon as the O is pressed the R turns into a Z.

In PRGM mode, pressing the XEQ key displays as XEY. Pressing shift CF displays as CF(_ _ the space between the CF and the _ _ is filled with ( . Pressing shift ENG displays as ENO _ . Pressing shift ISG displays as ISO _ . Pressing XEQ (which displays as XEY) then ALPHA DSE ALPHA results in DSM _ being shown.

Wild! :-)

I haven't analyzed the symptoms carefully, but my first guess would that either the RAM register that holds the lower seven bytes of the ALPHA register is flakey or the first display driver chip is flakey. I think that the program mode symptom indicates that it is much more likely to be in the display driver chip. If you have a service module, I would suggest using that to diagnose the problem.