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Anyone have ideas for batteries for these type of calculators? Edmund Scientific?
Message #1 Posted by gene wright on 6 Dec 2011, 12:58 p.m.

Edmund Scientific small calculators

These used a small battery pack that plugged directly into the wall to recharge. Anyone have an idea of refurbishing these? I plan to take it apart since the link above suggests it ran off coin cells. Perhaps I can simply use some alkalines...?

Ideas?

FYI. The one I have is the Edmund Scientific actual Scientific version that is missing keys in the picture. The one I now have is in great shape, but won't turn on. Batteries? perhaps...

      
Re: Anyone have ideas for batteries for these type of calculators? Edmund Scientific?
Message #2 Posted by Bill (Smithville, NJ) on 6 Dec 2011, 1:17 p.m.,
in response to message #1 by gene wright

Hi Gene,

I would think that standard button rechagable cells could be used to recreate the battery pack. Some of the Fujitsu Stylist tablet computers used a strip of 4 button rechargable batteries to maintain the clock and other settings while switching the main batteries. Not sure if Fujitsu directly sells replacement, but I would think they could be obtained from a battery distributer.

The harder part would be re-assembling the battery pack so that it could still be plugged into an outlet without risk of shocking yourself.

Bill

Edited: 6 Dec 2011, 1:18 p.m.

      
Re: Anyone have ideas for batteries for these type of calculators? Edmund Scientific?
Message #3 Posted by Bob Patton on 6 Dec 2011, 3:57 p.m.,
in response to message #1 by gene wright

You might look at American Science & Surplus (sciplus.com) item 36404.In the past I have bought several different kinds of such packs from them and disassembled them to get the tiny batteries inside. They won't be the button shape but they might fit in the space.

            
Re: Anyone have ideas for batteries for these type of calculators? Edmund Scientific?
Message #4 Posted by gene wright on 6 Dec 2011, 4:14 p.m.,
in response to message #3 by Bob Patton

Thanks guys.

I will gently disassemble the battery pack tonight and see what size "button" cells are in this thing. Be really nice to get this very well preserved tiny scientific calculator up and running.

                  
Edmund Scientific? (pictures)
Message #5 Posted by gene wright on 6 Dec 2011, 11:05 p.m.,
in response to message #4 by gene wright

Ok, who thinks they can repair this battery pack? :-)

The calculator is in such beautiful condition, it would be nice if it worked. Tomorrow, I plan to apply voltage to the calculator contacts to see if it works at all. If so, then battery pack repair is the next step.

Thoughts? Ideas?

Edited: 6 Dec 2011, 11:05 p.m.

                        
Re: Edmund Scientific? (pictures)
Message #6 Posted by robert rozee on 6 Dec 2011, 11:15 p.m.,
in response to message #5 by gene wright

to be honest, i'd seriously consider using three AAA or AAAA sized cells (whichever will fit), along with an external charger - or just make a holder that will take non-rechargables.

i'm afraid the current system employed, just series resistors and a diode, is inherently unsafe and sub-optimal in terms of battery health.

                        
Re: Edmund Scientific? (pictures)
Message #7 Posted by Thomas Chrapkiewicz on 6 Dec 2011, 11:19 p.m.,
in response to message #5 by gene wright

Gene:

Given the vintage of the machine and the I.C. inside (I believe I saw a TI part in one of the pics), it likely operates on about 5v. It appears that the silver contact is the positive (+), and the gold contact is the negative (-).

The pictures of the batteries (3 button cells in series) and circuitry appears to be some sort of half-wave rectified charging system. I would certainly NOT connect this to the 110VAC under any circumstances!!!!!!!!!!

Assuming that it will ultimately operate, it would be interesting to measure the current consumption, then figure out if more modern button cells (LR44 - NOT rechargeable) would be a viable replacement.

TomC

                              
Re: Edmund Scientific? (pictures)
Message #8 Posted by gene wright on 7 Dec 2011, 12:17 p.m.,
in response to message #7 by Thomas Chrapkiewicz

5V DC did not turn the calculator on here at the lab bench.

Might be dead. :-(

                                    
Re: Edmund Scientific? (pictures)
Message #9 Posted by Thomas Chrapkiewicz on 7 Dec 2011, 1:14 p.m.,
in response to message #8 by gene wright

Darn!

Can you verify that the on/off switch has good continuity?

TomC

                        
Re: Edmund Scientific? (pictures)
Message #10 Posted by Katie Wasserman on 7 Dec 2011, 5:34 a.m.,
in response to message #5 by gene wright

How about these cells? Do the dimensions match?

Or maybe switch to NiMH and get the V40H cells from The Nicad Lady. Ask her to weld some tabs on for you.


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