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ThomasF · (This post was last modified: 08-06-2021 05:33 AM by ThomasF.)

Hi SteveO!

The display in the classics consists of three modules with 5 digits each.
Most probable the first (leftmost) module is broken. I had a similar problem with a HP-55 calculator, where some segments in the middle module was lost.
In some cases it could be a bad connection, but then either the same segment in all digit is lost, or a complete digit, is this case it is neither.
And if you look with a magnifying glass you could also see that only parts if a complete segment (which to me looks like it consists of three smaller segments) light up - making a "dot" instead of a segment ("line"). (Probably more noticeably if you fill the display with "5" - it seems as if the top segment is only a "dot" in your case.)

Fortunately (depending on how you see it), the display module is the same in all classic models, so if you have the possibility to get some parts from another (non-functional) classic model, you can replace the single module that is failing.

This I did with my HP-55, I got a replacement module from a HP-45 that was broken, and I'm very happy with the result! Check the before and after pictures below!

Check out Teenix document (http://teenix.org/ClassicNotes.pdf) if you want some more information about the display in the classics - and if you have the possibility to replace it - remember the tip I got from Teenix that if the part gets too hot you risk damaging the internal LED segments as they don't like a lot of heat - but if you are familiar with a soldering tool - it should not be any problem!

Best regards,
Thomas