It's always a help when you can see the key you pressed during keystroke programming.

Looking at the comments here, I'm glad it wasn't just me that thought this calc feels more than just a _little_ slow. And by that I mean _glacial_ ... 😩😴 I'd like to see a followup video on overclocking this baby! I've seen some hints of such a mod online, and it's apparently quite simple. But so far my research hasn't turned up a howto. Thanks again for this excellent review, mate!

I have one that still works perfectly 40 years after I purchased it - The keys significantly yellowed over time but the screen still looks great and batteries last forever, at some point I had forgotten about it and they had bulged badly but were still working 10 years after I had installed them... I also had the unwieldy PC-200 printer that I purchased for printing programs that would eat batteries and used difficult to obtain special thermal paper, and that I positively hated to use... At some point I misplaced it and may have thrown it away, I don't remember, sorry for those here who are looking for one, I only used it for making program printouts that I still have in my old, pre-computer archives, but after 40 years they have become so faded they are almost impossible to read now with my declining eyesight.

Thanks for reviewing this fantastic calc, and for providing the link to my webpage! A small correction: the HP series you're comparing it to are the venerable Voyagers, not the Pioneers. I bought my TI-66 for just 10€ or so at a fleamarket _many_ years ago, not knowing what it was other than something programmable by TI (at the time I wasn't even familiar with the TI-58/59). I was pleasantly surprised -- THIS CALC IS AWESOME!!! As a bonus, it's beautifully designed too! Infact, it's probably my absolute fave from my collection. Compared to its ancestors, it boasts constant memory, alphanumeric display of program mnemonics (instead of numeric codes) and a mindbuggeringly colossal battery life -- I suspect mine still runs on its original Toshiba cells! On the downside, expandability is practically non-existent, save for a 2-line serial interface to the unobtainium PC-200 printer (I've only seen one on eBay in the last 15 years). But the biggest problem with this calc, as you point out here, is its ABYSMAL performance. It's without a doubt the slowest calc I've ever used, and by a huge margin, I guess that's the price to pay for the low battery drain. Many thanks again for this great review from a former Melburnian!

Did I mention this calc is awesome? 😁

Very nice! Thanks for the review. I love mine for the most part (I wish there was better, prompted I/O) despite its slowness.

Following along at home with my TI-66, mine seems to be a tad bit slower. It does feel good in my hands, and the build quality seems solid. One thing that I do find unforgivable is the lack of marker on the screen showing when you've hit the 2nd or the INV keys. Really guys?, how did you let that one slip through? As for the speed, I may have to bust mine open and do a RC time hack to speed things up. The HP Museum site has some teardown pictures: www.hpmuseum.org/forum/thread-2837.html?highlight=texas+ti-66 I only see two caps, giving me a fifty-fifty chance of getting the right one from the get-go (I'll probe it with my scope to see which cap is emitting the square wave). I also have the PC-200 printer that I'll have to try out one of these days. Apparently this is a rare-ish item? And my TI-66 is missing the same two rubber feet on the back. :) I bought mine in 2020 for 16.80 Euros and 4.90 Euros for shipping (why I bought this from a guy in France is anybody's guess) it was advertised as broken, but it works just fine. Excellent review as always. :)

Still have mine, bought at RIT in 1985. TI-55-II bit the dust after Expository Writing Class demonstration on how to disassemble things..oops. Still have the my 1959 Picket N4-T slide rule my father gave me too. I was using the TI-66 tonight and forgot how to program the keys....thank you. I have the Quick Ref Guide and cover pouch I carried it in college. Dang that was 40 yrs ago. (Also still have my Sinclair ZX81 from England).

I purchased my TI-66 when it first entered the market and it is still in good shape including all 4 rubber pads. I was wondering about the algorithm behind the program listing you supplied. I can't quite make out the name you spoke even though you said it twice. Could you please write it down. Thanks.

Excellent channel! Love to know where you source your calculators from in New Zealand! International I suppose. Been collecting vintage HP RPN calculators for a while now.

Thanks for the review, following the program you use as an example, once I reach step 007 and I hit the R/S key, it takes me back to the "0" screen. Any suggestions would be appreciated.

Mine doesn't start, only if i remove the batterie and install them again. The On button must be faulty.

Hi. I bought a Texas TI 66 in 1986 and it is new, because I take care of my electronics very well. But recently my calculator's batteries ran out. I would like to buy new batteries, but I don't know if I can take the risk of putting batteries with different voltage and amperage, because I couldn't find the calculator's specifications in the manual. Then, I would like to know if you may help me about the specifications of new batteries.