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Matt Agajanian · (This post was last modified: 10-24-2022 11:13 PM by Matt Agajanian.)

Hi all.

Two things I’m looking for. Since I haven't opened up my 28S in a long time, I forgot how to open the battery compartment door. In attempting to slide the door open, I did get the door off. I'm thinking that by luck my attempt to remove the battery door was correct. But it's not sliding back in place. Perhaps a chip or small piece broke off of the door.

OR, could it still be intact and I just need a refresher on how to put it back in place? As I said, it's been a while, so I'm a bit rusty on how the battery door is put on or taken off.

Does anyone have a spare battery door to send me? I'd appreciate it.

Yeah, not the best battery compartment/door design HP came up with.

Steve Simpkin · (This post was last modified: 10-25-2022 11:21 AM by Steve Simpkin.)

Did you look at illustrations for changing the batteries on pages 287-288 of the HP-28S Owner's Manual? They are pretty good.
The tricky thing about putting the cover back on is that you have to press down on the batteries while you slide the cover on. It is truly a terrible design.

https://literature.hpcalc.org/community/hp28s-om-en.pdf

BillBee · 10-25-2022, 11:00 AM

As Steve sez "it's tricky". Smile

If the door won't stay on then something is broken, but not going in means everything might be fine.

Here is how I close the door. Left hand thumb nail push down on the tops of the batteries to give you the clearance for the bat door. Then with the right hand line up the bat door and slide in.

Now from the pages of "do as I say not as I do" there is a way to use the small Voyager batteries (x3) with a wooden dowel to eliminate all the pressure of the current batteries. Its in the forum somewhere. I need to do the conversion myself sometime.

Hope that helps,
Bill

Steve Simpkin · 10-25-2022, 11:31 AM

Also as a general public service announcement. When buying "N" size batteries (aka E90) be sure not to accidentally purchase 12 Volt "A23" batteries instead. At a casual glance they look almost the same size but they will instantly kill a HP-41C or HP Clamshell calculator.

There should be a special place in "you know where" for the people that decided it would be a good idea to make the 12 Volt A23 battery almost the same size as the existing 1.5 Volt "N" battery.

mfleming · 10-25-2022, 11:35 AM

Another battery alternative is 2/3 AAA NiMH 400 mAh cells which are slightly shorter than N cells and thus impose slightly less pressure on the door when it is closed. Learned of this hack from a forum post, but haven't had enough morning coffee yet to find it Smile

Sylvain Cote · 10-25-2022, 11:57 AM

If you had look at HP Calculator Parts & Services you will have found that Marcel Beerli is making a 3D printed Champion battery door replacement. Wink

Matt Agajanian · 10-26-2022, 02:28 AM

(10-25-2022 11:31 AM)Steve Simpkin Wrote: Also as a general public service announcement. When buying "N" size batteries (aka E90) be sure not to accidentally purchase 12 Volt "A23" batteries instead. At a casual glance they look almost the same size but they will instantly kill a HP-41C or HP Clamshell calculator.

There should be a special place in "you know where" for the people that decided it would be a good idea to make the 12 Volt A23 battery almost the same size as the existing 1.5 Volt "N" battery.

I know that all too well.

I wrote a message about that in an earlier post.

Glenn Becker · 11-02-2022, 06:11 PM

(10-25-2022 11:57 AM)Sylvain Cote Wrote: If you had look at HP Calculator Parts & Services you will have found that Marcel Beerli is making a 3D printed Champion battery door replacement.

Has anyone tried to contact this provider lately? I have used several forms on the teawea.com website and all have failed to deliver a message.

As a last resort I tried emailing info@teawea.com (a guess, admittedly) and it bounced.

FWIW, I am also in need of a battery compartment door for a 28S.

Thanks,

Glenn

BillBee · 11-02-2022, 06:55 PM

(11-02-2022 06:11 PM)Glenn Becker Wrote:
(10-25-2022 11:57 AM)Sylvain Cote Wrote: If you had look at HP Calculator Parts & Services you will have found that Marcel Beerli is making a 3D printed Champion battery door replacement.

Has anyone tried to contact this provider lately? I have used several forms on the teawea.com website and all have failed to deliver a message.

As a last resort I tried emailing info@teawea.com (a guess, admittedly) and it bounced.

FWIW, I am also in need of a battery compartment door for a 28S.

Thanks,

Glenn

In the past I would just buy a financial clam shell model and use the door. They can be really cheap. If you can find a non-functional one they are even less.

-Bill

Glenn Becker · (This post was last modified: 11-08-2022 10:12 PM by Glenn Becker.)

(11-02-2022 06:55 PM)BillBee Wrote: In the past I would just buy a financial clam shell model and use the door. They can be really cheap. If you can find a non-functional one they are even less.

-Bill

Brilliant suggestion - I checked that auction website and there are some good candidates. This would appear to be the most economical route! Thanks!

UPDATE: I wound up ordering an 18C in 'unknown' state (the seller hadn't bought any 'N' cell batteries to test the unit) for less than $10. It feels a little weird to sacrifice a possibly-working calc (I haven't tested it yet, myself) ... but I'm much less interested in the 18C than I am the 28S.

G