HP-67 weird program editing problem

[Hiwi]

Hi,
i have a nice overhauled HP-67 that is working apparantly good. I can read magnetic cards with programs from my HP-97, they deliver results as expected.
I have not found any problems even larger programs are working.

Yesterday, i tried to alter a program (which has approximately 120 lines of code).

At the beginning I deleted some lines with f DEL and inserted new ones, such as 100000 => EEX 5, to save some space. Or changing values e.g. from 240 to 260.

Editing works, but the result is that the program content changes at other higher RAM cells, so the program is totally corrupted.

It is reproducible on lower ram content, over step 120 there are no abnormalities, so far my first observations.

I tried the diagnostic card from the standard pack, no failures.

What can I check now?
Is there a ram failure of ROM 1 or 2?

I had a HP-97 with ram failure, but there i had already problems when the program was running.

Can anyone help?
Ralf

[teenix]

If the diagnostic worked, then it sounds like a ROM problem. However, tracking it down might be difficult, as 4 of the 5 ROMs are used to execute code for program editing.

cheers

Tony