HP-27 display

[Steve Simpkin]

(09-19-2018 11:23 PM)DANTONVB Wrote:  I just received an HP-27 calculator in almost new condition. I'm using NIMH Eneloop AA 2000mAh batteries in it. Sometimes, after turning on the display, it is displayed as the attached image. After pressing any key, the calculator's behavior is normal, as expected. Any ideas on that?

That is the "Low battery" indication for the 20 series models. The decimal points are "inverted" (on for all digits except where the decimal point should be on). I used to see that sometimes after turning on my HP-25 when running on mostly worn out alkaline batteries.
How new are your Eneloop batteries?
Perhaps try a different set.