(INVENTORY REF. 68-18)

This listing is for a nice 1990 Texas Instruments TI-68 Algebraic Scientific Programmable Calculator (I would assume you’re already familiar with or are searching for this particular vintage calculator if you’re viewing this listing):

Seller notes:

This an extremely nice collectible and one of my all-time personal favorites – amazingly powerful and innovative for its time!  Marketing guys called this calculator “Advanced Scientific“, others call it “almost programmable“.   At first glance the TI-68 seems to be a perfect calculator!  A clear, alphanumeric display with a width of 12 digits, up to 55 memories or 440 programming steps and a calculation precision of 13 digits.  Compared with the TI-60 you have only the limited programmability of a formula-based machine and the maximum size of a program is only 79 steps. Another drawback is the overloaded keyboard with a 2nd, 3rd and ALPHA key. On the pros you get a lot of complex number functions and powerful equation solver. Nevertheless, the TI-68 was a very successful calculator and produced from 1989 until 1999.

To reduce the manufacturing costs of the calculator some mechanical and electrical changes were introduced with the TI-68 (1991) model. At first glance you recognize that the metal bezel of the first edition was replaced with a plastic bezel.

The backside of the calculator reveals another method of cost reduction. The screws to fix the housing parts together were replaced with a snap-fit construction.

Even the inside construction of the two calculators is different.  Instead, the screws to hold the printed circuit board (PCB) in the bottom housing we notice the heat-stamped pins. The calculator circuit itself is identical with both models.

In 1995 part of the production of the TI-68 was shifted to Malaysia and later to China, compare the differences here.

The TI-68 is one of the early calculators using the EOS or Equation Operating System compared to the original AOS system developed with the SR-52. The TI-68 lets you enter an expression into the entry line the same way as you would write it. You can move through the entry line to review or edit any part of the expression before evaluating it. Most of the information about entering and editing applies both to equations and formulas.

Please read the TI-68 review from "Eddie's Math and Calculator Blog" at:  https://edspi31415.blogspot.com/2017/07/retro-review-texas-instruments-ti-68.html

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TI-68 FEATURES:

Formulas and Integration

Alphanumeric Variable Names

Polynomial Roots

Statistics with Linear Regression

Choice of Number Bases Calculation Flexibility

Constant Memory™ Feature

APD™ -- Automatic Power Down Feature

The calculator has 440 bytes in 55 registers of memory space, enabling you to save simple or sophisticated calculation tasks. Entering your own formula is easy because it is much like entering an ordinary calculation.

After entering a formula, you can evaluate or integrate it.

You can use meaningful abbreviations for the names of variables and formulas. A name can be letters or a combination of letters and numbers.

Given the coefficients of a second-, third-, or fourth-order polynomial, the calculator finds all real and complex roots of the polynomial.

You can enter a data set of either one- or two-variable observations. The results depend on whether the data set is one- or two-variable entries. For a two-variable data set, the calculator determines a regression line.

In addition to the decimal number system, the calculator enables you to perform integer operations with hexadecimal (base 16), octal (base 8), and binary (base 2) numbers. You also can convert between number bases.

By including three selectable angle units and conversions between them; along with settings for standard, scientific, engineering, and fixed-decimal notation; and also a set of symbols that give special meaning to a number, the calculator gives you control over the appearance of entries and results.

When you turn off the calculator, the Constant Memory™ feature retains the entries you have stored so that you can use them when you turn the calculator on again.

To extend the life of the calculator's battery, the APDT™ Automatic Power Down feature automatically turns off the calculator after a few minutes if you do not press a key. You can resume operation by turning on the calculator.

 

Alphanumeric

Display

The display uses letters, numbers, and other symbols to show calculation entries including function names, operations, numeric values, and commands. Some activities help you along by placing prompts in the display. The display also has numerous indicators to show you the current settings and status.

Solutions to a System of

Simultaneous Equations

The display prompts you for the coefficients and labels results, making it easy to enter and solve a system of simultaneous equations. The system can be up to fifth order, with either real or complex coefficients.

Extensive Complex Numbers

The TI-68 allows you to perform calculations with complex numbers in a natural, straightforward sequence. The functions that can handle complex numbers include arithmetic, reciprocal, powers and roots, logarithms, hyperbolic functions, and trigonometric functions. Real numbers and complex numbers can be used easily within the same calculation.

While most other calculators stop with an error when a complex number should result, the TI-68 excels by providing a complex result.

Choice of

Complex Number

Forms

Because you may need a resulting complex number to be displayed in rectangular form or in polar form, the calculator has settings for both forms. An entry also can be in either form. You can even convert a complex number between the rectangular and polar forms.

Last

Equation

Replay

Allows recalling, checking, and editing of the last calculated equation. Allows you to replay the previous equation even if you have started a new equation.

Convenient

Functions

In addition to the many standard scientific functions, the calculator has built-in combinations, permutations, hyperbolic functions, and metric conversions.

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Why buy a vintage (or any) scientific calculator from me when you might have other choices?  If my prices are just a bit higher than the average at times, please consider these valuable points:

  1. First, I grew up in the 60s and 70s and been using scientific calculators since 1972 and am familiar with most of the Texas Instruments, Hewlett Packard, Sharp, and Casio scientific models since I probably have owned many of them since that time!
  2. I have collected calculators for many years so I am familiar with what to look for, what has become more valuable, what to look for – and what to avoid.  Though not an “expert”, I am reasonably knowledgeable and experienced.
  3. I have acquired a TREMENDOUS repository of resources, manuals, and information for vintage calculators so I can provide some direction to my buyers.  IF I HAVE A .PDF MANUAL(S) FOR THE CALCULATOR IN THE LISTING, IT WILL BE INCLUDED IN THE LISTING (WITHIN E-BAY 10MB LIMITATIONS) AS A SERVICE FOR MY VALUED BUYERS.  If the .pdf file is too large for the E-bay listing limitations, I will supply a link for this calculator’s download(s) when the calculator is shipped.  This potentially saves my buyers a lot of time and searching.
  4. I DESPISE things that don’t work properly – especially when purported to be working.  As a seller, I pledge to my buyers that I try my best to make sure items work properly prior to selling.  I don’t claim to be perfect at it (and yes I will miss some things occasionally), but if something is truly wrong I will attempt to resolve it to customer satisfaction – even if at my expense.  If I discover anything that might not be working as it should, the listing will include that information as full disclosure and the item likely discounted accordingly.  I do not claim to test every function of every calculator I sell, but experience generally tells me if they are working as they should.
  5.  I DO NOT list used calculators that are:
    1. “Untested” (??!!) – your purchase will NOT be a crapshoot!
    2. Listed as “used” but “sold as is” – no display, no mention of even if it turns on or much less even works! (should be listed as “for parts or not working” instead of “used” as per E-bay definitions)
    3. “Turns on!” does not necessarily equate to “working”!
    4. “Needs [new] batteries”, “no batteries”, or “batteries not included” – REALLY?? (how do you know it even works then?!)
    5. “Found after 20 years in grandpa’s 100 degree attic and looks clean on the outside”…(you get the idea)
    6. Obviously have been abused by the previous owner(s) (FYI…I am the second owner of this calculator listing unless I specify otherwise)
    7. “Works perfectly!” (but the display reads “66666666” when it should be 88888888 because LED/LCD segments are missing
    8. Have known working defects that prevent the calculator from functioning as it should – those calculators would only be listed as “for parts or not working”
  6. I DESPISE wasting shipping charges!  Though my shipping costs are always free, I don’t want to waste my time and money shipping non-working items any more than you want to receive them!
  7. I DESPISE corrosion – especially with electronics!  I inspect all battery contacts of all calculators and clean them as much as possible so that they are in good working condition.
  8. I DESPISE dirty, grimy calculators that look as though they’ve lived and been handled in an auto shop and any I sell will be cleaned as much as is possible without overcleaning that may damage components, finishes, keys, or displays.
  9. I install NEW TESTED batteries as needed and test/inspect the batteries before shipping my calculators so the buyer doesn’t have to be concerned about that!  Even if the calculator is dual power (i.e., solar and battery power) those batteries are replaced as well
  10. I pack and ship items all over the world – my items sold are packaged securely
  11. Nearly all my listings will be individual listings instead of a “representative listing” (e.g., if I have five HP-22S calculators, I provide a bunch of representative pics, and you get one of the five).  It takes more time to list each one but that’s because I care.
  12. If you don’t see a current listing in my store and you’re looking for a particular vintage scientific calculator, I may have one but have simply not listed it yet or had time to do so.  If you message me through a listing and ask, I can provide you with that information.
  13. My listing prices take into account availability (rarity), overall functionality, overall cosmetic condition, my E-bay seller’s fees, and always free shipping within the CONUS (I do not believe in making profits by listing at a lower price then adding ridiculous higher-than-necessary shipping fees to make up the difference)
  14. There are reasons why I have a “preferred seller” rating on E-bay – I value my customers and reputation more than making a few dollars as a part-time small business for a retired grampa!
  15. If you don’t find a vintage calculator listing in my store to your liking, I would highly recommend you check out VINTAGE CALCULATORS, INC. https://www.ebay.com/str/vintagecalculators?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=R9U0TOR4S8a&sssrc=3418065&ssuid=Uvs5gYFZT-m&widget_ver=artemis&media=COPY as a superb and reliable source for vintage calculator and vintage calculator parts!

NOTE TO BUYERS:  I have a rather strict no-returns policy (as with my airguns) as I have no control with what customers do to items once received.  Once you buy it you own it, and once you receive it intact it becomes yours to do with whatever you wish.  The only exception is if the item it delivered damaged (which should be rather rare) and that the buyer can provide proof (and pics) at the time of delivery.  I have had some unscrupulous airgun buyers in the past who actually removed parts, then claimed the airgun was not functioning properly, etc.  This is for my own protection as a seller as I am not a huge retailer and cannot afford “buy and try” situations.  I hope you will understand and as a small personal business cannot afford to do otherwise.  However, as per above, if something is really wrong or you believe I’ve somehow misrepresented the item, I WILL make it right as my pledge to the buyer. 

Also, I do not give calculator lessons and there is a learning curve for any scientific calculator.  If not already included in the listing, all user manuals for calculators that I sell can easily be obtained online for free, so that may fall on your responsibility as the new owner.  I am only one person and my E-Bay store is not my life ;) – but I do take pride in it!  I must also ask for the same time-constraint reasons that you limit your questions to the listing itself as my listings are not a vintage calculator forum or chat room ;)

Please ask any questions prior to purchasing and thanks for looking!