Texas TI-59 reading card error

[DANTONVB]

I just bought a TI-59 in very good condition. It is operating very well, except when reading magnetic card. In writing card operation it return the number of memory bank, without blinking, as specified in user manual. When reading the magnetic card it returns a blinking number, sometimes the number one, sometimes a double digit number as 41, 23, 36, 62.

The card speed seems to be ok, as specified in the service manual page 11 (X letter in TEXAS when writing card).

Any ideas on the error?

[Hiwi]

This is an very old post, but there was never posted a solution.
I had similar problems with REV 3 Boards, and as mentioned in the service manual you can solve this problem in most cases with a slight modification.

Open the calc, take out the main pcb and locate the pin 21 of the display (last pin, leftside, pin 1 is marked) cut the connection cautious and connect the open ends with a diode, TI stated a PG1922, but it is not available anymore. The replacement is a NTE512 and this is a standard 1N4148!

Other problems when reading may be solved with some (4) small 100-150pf capacitors soldered from pin1 to pin2 ... on the cardreader connection on the main PCB.

I saw this mod only once on an Rev 5 board.

Ralf