HP-97S trouble: shown 0. 00 instead of 0.00

[Trevor Gale]

BY coincidence, I went to use my HP-97 today and at first it worked just fine, including programming and writing / reading the cards.

Then it started to show exactly the same issues as you show in your video; at first I assumed it might be a low battery but I checked in my workshop that and it was not the case.

Sometimes it will return to "normal" operation, then if I do a line-feed on the printer button it will revert to the same problem.

I opened up the calculator to check for anything obvious and I lifted and replaced the logic PCB board a few times (moving the multiple gold connector pins in the plated-thru holes in the PCB) to maybe clean them a bit.

For a while after that it worked fine again; so I know that the various ROM's must be working as well. I am thinking that those connector pins onto the holes at the bottom of the logic board may be the source of the trouble. One CANNOT solder these in any effort to ensure good permanent contacts, because then the logic board would never be able to be removed again.

Perhaps it might be an intermittent "dry joint" on the ROM concerned, but I will have to examine this in my workshop tomorrow or later - if so I can easily re-solder these pins, but I fear that it is those connector pins to the bottom of the logic board... Has anyone any ideas of making sure they make good contact???