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jebem · (This post was last modified: 09-26-2019 02:15 PM by jebem.)

So I saw this nice Texas TI-66 Programmable calculator for sell in one of our local auction sites, complete with documentation, pouch, and original packaging.
The asking price was so low that I could not resist myself to acquire yet another machine, even if it is coming from the dark side (I wonder why Texas is refereed as such in a few forums?)

The calculator itself is near mint condition, just showing tiny scratches here and there.
The manual is as new, probably never used, and the packaging is in excellent condition.

It seems that this calculator was outsourced to Toshiba. The main PCB has the Toshiba label screened to the copper layer and the SoC chip is a Toshiba T6875A from 1986.

The memory chip is a 1024 x 4-bit words CMOS static RAM TC5514AP-3 in a DIP-18 package from 1985.

As usual for machines that are not sealed (unlike many HP models using plastic rivets to seal the case and taking the fun away from this hobby), I have dismantled it piece by piece for inspection and cleaning.

To open the case it is enough to remove one single screw from the back cover.
To remove the pcb it is enough to remove a few screws.

One excellent engineering solution found by Toshiba is the LCD display connection to the main PCB - a metal bracket is used and maintained in place using 3 screws.
This method is efficient and expensive to manufacture, so Texas/Toshiba didn't cut costs here.

Another excellent feature are the costly injection molded keys. Considering that in the 80's most of the manufacturers were using painted keys, this is a nice touch from Texas.

Edit:
Here is a review in the Eddies's Math And Calculator blog

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**Katie Wasserman** · 01-11-2015, 06:36 PM

Nice pictures. thanks for the tear down!

I hope that you got all the keys back into the correct locations Smile

I've messed that up several times before I started putting the calculator face down on my scanner and printing off a copy to go by when replacing the keys. Now I always do that before opening up one of these things just in case the keys start falling out.

jebem · 01-11-2015, 06:41 PM

My calculator as made in Japan in 1986 as shown in the back label.

This is a kind of alphanumeric calculator - It displays the actual programming codes names instead of its numeric codes.

Time to assemble all the parts and take one last set of photos.
It is past 17h00 in Lisbon region and the light conditions do not help.
But I have spent my day touring old familiar places in Sintra area. This time I revisited Lagoa Azul to have a nice walk in the woods by the lake.
So only now I have the time to take the photos and upload them.

jebem · 01-11-2015, 06:49 PM

(01-11-2015 06:36 PM)Katie Wasserman Wrote: Nice pictures. thanks for the tear down!

I hope that you got all the keys back into the correct locations I've messed that up several times before I started putting the calculator face down on my scanner and printing off a copy to go by when replacing the keys. Now I always do that before opening up one of these things just in case the keys start falling out.

Hi, Katie,
Thanks for your feedback!

Oh yes, I have been in trouble more times than I can tell, but luckily now we have Internet Smile

This time I have lost one of the two tiny small springs shown in the initial photo of my OP, when trying to put it back into the power On key.
The damn thing just jumped in front of me and I'm afraid it's gone for good.
After spending 1 hour looking around I have quit my search and have just assembled the unit without it.
Apparently it works fine. But I know it is missing, and this will bug me for a while.

Thomas Radtke · 01-11-2015, 07:11 PM

I bought one just for its beauty. Most calculators have been stored away after I quit collecting, but the TI-66 is still around. Congratulations for finding such a nice sample - mine looked like it came straight out of a landfill (it probably did, as the seller called himself "Recyclinghof" :-D).

Mark Hardman · (This post was last modified: 01-11-2015 07:17 PM by Mark Hardman.)

Jose,

The springs likely provide grounding between the circuit board and the metal face-plate on the keyboard. Early Voyagers used the same system.

I would like to thank you for the content and quality of you frequent photo essays. It never fails that I learn something new.

I look forward to this and your future offerings.

Thomas Klemm · 01-11-2015, 07:38 PM

I bought one of those to my sister when she was still in high school. I think I liked that the display was similar to the HP-41 and it was programmable. She gave it to me years later. I never realized that there was a printer to it. If I remember correctly, the programs were running quite slow.

This picture is from datamath:
[Image: TI-66_PCB.jpg]

Cheers
Thomas

Marcus von Cube · 01-11-2015, 08:03 PM

(01-11-2015 07:38 PM)Thomas Klemm Wrote: I never realized that there was a printer to it. If I remember correctly, the programs were running quite slow.

The latter is right but can be remedied by a simple modification to the RC circuit. Sorry, but I can't find the instructions on the net anymore. Maybe Katie has a clue.

The printer is timing dependent. With a sped up TI-66 it no longer works.

walter b · 01-11-2015, 08:44 PM

(01-11-2015 06:41 PM)jebem Wrote: My calculator as made in Japan in 1986 as shown in the back label.

This is a kind of alphanumeric calculator - It displays the actual programming codes names instead of its numeric codes.

Muito obrigado for this comprehensive photographic documentation. The Pioneers (e.g. HP-32S and HP-42S) were alphanumeric calculators alike.

Quote:But I have spent my day touring old familiar places in Sintra area.

Very nice area indeed Smile

d:-)

jebem · 01-11-2015, 09:00 PM

(01-11-2015 07:11 PM)Thomas Radtke Wrote: I bought one just for its beauty. Most calculators have been stored away after I quit collecting, but the TI-66 is still around. Congratulations for finding such a nice sample - mine looked like it came straight out of a landfill (it probably did, as the seller called himself "Recyclinghof" :-D).

Dunke, Thomas!
I have got my fair share of Recyclinghof's units as well, acquired to private sellers around Portugal.
Usually the sellers here try to beautify the goods in the best way they can, and when I finally meet them usually in a public place, I found out the hidden issues... but usually I buy the defective goods because the asking prices are on the low side.

(01-11-2015 07:15 PM)Mark Hardman Wrote: Jose,
The springs likely provide grounding between the circuit board and the metal face-plate on the keyboard. Early Voyagers used the same system.

I would like to thank you for the content and quality of you frequent photo essays. It never fails that I learn something new.

Hi, Mark,
Thanks for your kind words. You are very welcome.
I just fill the need to share what I can find for my collection.

Concerning the tiny springs:
You are right. And it makes all the sense.
Thank you!

I know about it because even the old Casios did the same.
What was I thinking this afternoon?
I know, red wine and electronics do not match well...

jebem · 01-11-2015, 09:40 PM

(01-11-2015 08:44 PM)walter b Wrote: Muito obrigado for this comprehensive photographic documentation. The Pioneers (e.g. HP-32S and HP-42S) were alphanumeric calculators alike.

Quote:But I have spent my day touring old familiar places in Sintra area.

Very nice area indeed

You are welcome, Walter!
I have already one HP-32SII and one HP-42S. Very nice machines, in a different league from the humble TI-66!

Sintra area can be wonderful in a bright sunny day as it was today.
Usually the region is covered with fog, but not today.
Can you believe that today by 12h00 the temperatures rose to 18 degrees Celsius at the sea side?
There were lot of people on the beach as well!!!
Unbelievable, considering that three days ago we got freezing temperatures during the night!

jebem · (This post was last modified: 01-11-2015 09:53 PM by jebem.)

(01-11-2015 07:38 PM)Thomas Klemm Wrote: I bought one of those to my sister when she was still in high school. I think I liked that the display was similar to the HP-41 and it was programmable. She gave it to me years later. I never realized that there was a printer to it. If I remember correctly, the programs were running quite slow.

This picture is from http://www.datamath.org/Sci/Galaxy/TI-66.htm

Cheers
Thomas

Hi, Thomas,
Thanks for your input.

Datamath.org is one of my preferred information sources. So much information available for free! We have to thank Joerg Woerner for that.

The printer is one item that I'm planing to acquire one of these days, depending on the opportunities and available funds Smile

Slow it is. The upside is that the battery cells apparently last for ages.
The previous owner never replaced the batteries and he did use it for a few years in the university.
When I took them out the weaker one had around 1.35Volt (nominal 1.5V), and the calculator seems to be working fine with them.

**Gene** · 01-11-2015, 10:04 PM

The TI-66 is such a beauty, but SO SLOW.

But I do hate machines with shifted trig functions!

More info: Ti-66

**Katie Wasserman** · 01-11-2015, 11:41 PM

(01-11-2015 06:49 PM)jebem Wrote: After spending 1 hour looking around I have quit my search and have just assembled the unit without it.
Apparently it works fine. But I know it is missing, and this will bug me for a while.

If you're like me it will bug you until you step on it and it gets caught in either your sock or worse your foot!

**Katie Wasserman** · (This post was last modified: 01-11-2015 11:53 PM by Katie Wasserman.)

(01-11-2015 08:03 PM)Marcus von Cube Wrote:
(01-11-2015 07:38 PM)Thomas Klemm Wrote: I never realized that there was a printer to it. If I remember correctly, the programs were running quite slow.

The latter is right but can be remedied by a simple modification to the RC circuit. Sorry, but I can't find the instructions on the net anymore. Maybe Katie has a clue.

Unfortunately I don't have a TI-66 (I do have some of the others, like the TI-65, 75, 95) so never played with the clock in there. I have played with the clock in the HP voyagers though, it's pretty easy to speed those up by a factor of 2 or so.

BobVA · 01-12-2015, 12:01 AM

(01-11-2015 11:41 PM)Katie Wasserman Wrote:
(01-11-2015 06:49 PM)jebem Wrote: After spending 1 hour looking around I have quit my search and have just assembled the unit without it.
Apparently it works fine. But I know it is missing, and this will bug me for a while.

If you're like me it will bug you until you step on it and it gets caught in either your sock or worse your foot!

May I suggest a sweeping the floor with a large magnet? Those removed from hard drives are ideal.
This has recovered many watch parts for me, save the few that clearly jumped through some kind of dimensional portal to another universe. Or wound up in my shoelaces (happened!)

Bob

Mark · 01-12-2015, 06:36 AM

Hello,

Using a magnet to catch small parts on the floor saved my day many times...

But I wouldn't use this method with mechanical watch or clock parts. I've always read or heard about nasty effects if some gear gets magnetized (especially on very old mechanisms), which can cause irregular functioning. I really would like to get some advice from a watch / clock expert ?

Marc

BobVA · 01-13-2015, 01:00 AM

(01-12-2015 06:36 AM)Mark Wrote: I've always read or heard about nasty effects if some gear gets magnetized (especially on very old mechanisms), which can cause irregular functioning. I really would like to get some advice from a watch / clock expert ?

Marc

You make a good point - magnetized parts in a mechanical watch can cause a variety of ills, so it's always prudent to take a quick look before breaking out the magnet.

Fortunately there are a variety of gadgets that can be used to demagnetize the recovered part, if necessary.

grsbanks · 12-16-2017, 10:17 PM

An old thread, I know, but I've recently acquired a TI-66 from TAS. I used to own one 20+ years ago so there's an element of nostalgia in there.

Anyway, mine is misbehaving. It's reporting incorrect keypresses and getting rather confused.

Inspection of the machine's guts reveals some battery leakage and corrosion of the RAM chip's pins around its data bus (pins 5-8 of the TC5514APL-2). My guess is that this is what's responsible for the problem, anyway. I have a new RAM chip on its way so I can take the other one out, clean up the PCB and repair any tracks that might need it and I'll report back once that's done.

**rprosperi** · 12-17-2017, 02:45 AM

(12-16-2017 10:17 PM)grsbanks Wrote: An old thread, I know, but I've recently acquired a TI-66 from TAS. I used to own one 20+ years ago so there's an element of nostalgia in there.

Anyway, mine is misbehaving. It's reporting incorrect keypresses and getting rather confused.

Inspection of the machine's guts reveals some battery leakage and corrosion of the RAM chip's pins around its data bus (pins 5-8 of the TC5514APL-2). My guess is that this is what's responsible for the problem, anyway. I have a new RAM chip on its way so I can take the other one out, clean up the PCB and repair any tracks that might need it and I'll report back once that's done.

I don't collect too many TI machines, but this is one of the ones I do have. These landscape machines 65, 66, 67 are nice (but slow!). I can send it so you can compare with a working unit if that will help, assuming the RAM doesn't fix it. Holler if you need it.