HP80 with (apparently) defective display

[aurelio]

"Stay at home" everywhere is the best advice you receive in these times.
What a chance for any enthusiast to dedicate a little more time to the home and why not also to the small collection of HP calculators?
What a bad thrill when while performing a calculation with the HP80 I found a problem in displaying the number 8, due to a missing segment in the centre of the digit and when I realized that the same missing segment was out in every digit across the display, I thought it could be due to a malfunction of the anode driver chip, as indicated from a member in a old archived post.
Attempting to open the calculator and to check inside, I noticed, just after removing the battery compartment cover that the digit suddendly appeared complete again and it seems to be due to the pressure and (I assume) to the variable contact of the battery. I restored with a tool the tension of the contact springs and the display works regularly.
How could be explained this behaviour?
Can a minimal variation of the input voltage , determinate a defect in the display circuit?

edit: typos

[teenix]

It might have been caused by a voltage drop caused by the poor battery contact. It may have interfered with the way the digit drivers work.

Sometimes connecting an oscilloscope causes display problems also.

cheers

Tony

[BobVA]

...or perhaps there is an intermittent / dirty connection between the display and the main board and the small amount of flexing involved in removing the battery cleared it up?

If it comes back I'd first clean all the board / display interconnects. (If you have the schematics you can isolate that segment connection for a particular look.)

[aurelio]

(03-20-2020 03:03 PM)BobVA Wrote:  ...or perhaps there is an intermittent / dirty connection between the display and the main board and the small amount of flexing involved in removing the battery cleared it up?

If it comes back I'd first clean all the board / display interconnects. (If you have the schematics you can isolate that segment connection for a particular look.)

thank you Bob, but the problem disappeared assureing a regular contact between the springs and the battery, not just moving or bumping the components.
I prefere to do not open it if not absolutely necessary...

[BobVA]

ALWAYS a good policy :-)

(And I should have said the "keyboard/display to main board" interconnect.)