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Thread: Vintage calculator guys? Some help with a Texas SR-51A

  1. #1
    Grand Master JasonM's Avatar
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    Vintage calculator guys? Some help with a Texas SR-51A

    I know there are some vintage tech guys on here, last weekend I picked this up at a car boot sale, 1970s ( I presume ) Texas Instruments SR-51A, only to find out when I got home its doesn't take normal batteries, its a rechargeable battery pack meant to be used with a power supply, the cells are AA sized but its not a simple matter of dropping them in, the connectors are soldered on to make the circuit, doing some research, there are aftermarket modified packs that can take the AAs but as I don't know if it even works Im loath to buy one ( from the USA it seems ) until i know it works. Looks pretty clean inside and the cells hadn't leaked so Im optimistic.
    Does anyone here have one that would be willing to take mine and test it with their BP1A working pack ?
    I couldnt leave it behind for the sake of 80p It even has a case.



    Cheers..
    Jase

  2. #2
    Master
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    Long shot but there’s telephone numbers here and they might be able to help or direct you to someone who can??

    https://education.ti.com/en/customer...port-worldwide

    EDIT: Actually….

    https://education.ti.com/en/customer...ormation/12678

    http://www.datamath.org/Batteries/BP1_Repair.htm
    Last edited by David_D; 20th November 2022 at 14:47.

  3. #3
    Can't you just rig up some AAs with bit of wire etc for testing?

  4. #4
    Grand Master JasonM's Avatar
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    Thanks both, yeah, I did rig up some AAs and tin foil but wasnít a very good try to be honest, I might have a proper go at that again I guess.
    Cheers..
    Jase

  5. #5
    Master Skier's Avatar
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    Quote Originally Posted by JasonM View Post
    Thanks both, yeah, I did rig up some AAs and tin foil but wasnít a very good try to be honest, I might have a proper go at that again I guess.
    Just don't use regular, disposable 1.5v AAs. These came with 3 x 1.2v NiCd batteries so ensure you use 1.2v rechargeables. Good luck.

  6. #6
    Craftsman DONGinsler's Avatar
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    Would a US charger have the right plug system for the UK?

    Calc and charger on Ebay for $15.00 with free standard shipping in the US.

    Cost to you in the UK though. Any body's guess. probably not worth it if not going to be used

    https://www.ebay.com/itm/17548988571...Bk9SR4i0tIaTYQ

  7. #7
    You need three NMih rechargeable cells, like these:
    https://www.amazon.co.uk/gp/product/...KL5A1OLE&psc=1

    A battery box like this:
    https://www.amazon.co.uk/4-Pieces-Pl...ps%2C94&sr=8-4

    And possibly a charger like this, if you don't have the calculator's power pack.
    https://www.amazon.co.uk/OocciShopp-...ps%2C93&sr=8-9

    It should be obvious hot to hook that lot up.

  8. #8
    Craftsman
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    I have a Texas TI1706 light powered calculator in the junk draw from the early 80s. Still works. Was my dads and I canít remember a time when it wasnít around. Funny how these things crop up.

  9. #9
    if the cells or any electrlytic capacitors inside have not leaked on the PCB then there's a great chance you get it working again.
    Replace the electrolytic capacitors anyway (if it has any) worth it for the 80p and if you spend some time and a few quid on batteries and it still won't work then you're still in profit.

  10. #10
    Grand Master JasonM's Avatar
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    Cheers guys, no sign of leaking so fun little project and as you say, not much to lose, part of the - tab terminal has snapped off in the board but thereís plenty left to solder a new bit on.
    Cheers..
    Jase

  11. #11
    Grand Master Mr Curta's Avatar
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    Fingers crossed. My Dad had a TI-59 programmable but I suspect that it's long gone.
    Don't just do something, sit there. - TNH

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