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HP-27 display
09-19-2018, 11:23 PM
Post: #1
HP-27 display
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?


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09-19-2018, 11:28 PM
Post: #2
RE: HP-27 display
The "new" HP-27 and my old HP-27S side by side. Both are the two multipurpose calculators from HP.


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09-20-2018, 12:18 AM
Post: #3
RE: HP-27 display
(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.
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09-21-2018, 12:59 AM
Post: #4
RE: HP-27 display
Thanks for the information. I put fully charged batteries and the problem is gone.
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09-21-2018, 12:22 PM
Post: #5
RE: HP-27 display
And for the record in case someone reads this thread in the future...

NEVER charge any woodstock battery pack with the battery pack in the calcuator and using the external AC Adapter.

Big NO for the HP 21, HP 22, HP 25, HP 27, HP 25C, HP 29C.

Don't do it.

DantonVB may not have done it :-) but in case someone reading this thread years later does not know already...don't!
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09-21-2018, 02:36 PM (This post was last modified: 09-21-2018 02:39 PM by burkhard.)
Post: #6
RE: HP-27 display
(09-21-2018 12:22 PM)Gene Wrote:  And for the record in case someone reads this thread in the future...

NEVER charge any woodstock battery pack with the battery pack in the calcuator and using the external AC Adapter.

Big NO for the HP 21, HP 22, HP 25, HP 27, HP 25C, HP 29C.

Don't do it.

DantonVB may not have done it :-) but in case someone reading this thread years later does not know already...don't!

Wonderful HP27 you have!

To be clear, that "external AC adaptor" Gene mentions above is not an AC Adaptor really. It is a charger. If you attempt to run the calculator with it and no battery (OR a failed battery OR a battery that is just making poor contact with the terminals OR the calculator gets jostled or dropped of the desk under charge), the calculator gets instantly and fairly catastrophically damaged. It can be repaired, but it's work and $$$/€€€, probably as much as it cost to buy in the first place.

It is better to NEVER use that charger at all and to instead charge the AA batteries off-board in a modern NiMH charger (better suited for modern battery chemistry anyhow). The factory HP charger is evil and the reason why at least 3/4 of all the Woodstock series calculators for sale on eBay are hosed. I have mine tagged "HP-25 charger. NEVER use -- can damage calculator. Save for historical purposes only" so when I pop off some day, my heirs won't break all the Woodstocks when they evaluate my stash. Sooner or later there will be no unbroken Woodstocks.

The Spice series has the same problem I think, right?
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