HP 9872T Trouble Shooting

[husmann]

(06-10-2018 10:49 PM)husmann Wrote:  Thanks a lot for all your hints. I’ll need some time to check them all. As soon as I have completed them I’ll post my results here.

Finally I managed to have a few minutes to return to my sick mechanical pet. My results:

• reseating ROMs U55 and U56 had no effect

• photos of the clock signal at pins 5 and 6 of clock divider U60 can be downloaded at http://huswelt.de/HP-9872T/HP-9872T.zip - the photos are taken from a borrowed simple oscilloscope

Thanks, Wolfgang