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Texas TI-66 Programmable: Toshiba skills to rescue Texas...
12-17-2017, 08:29 AM
Post: #21
RE: Texas TI-66 Programmable: Toshiba skills to rescue Texas...
Hi,

I have a TI-65 in a very good shape and working condition, but on the LCD some annunciators and the segments of exponent display don't lit. And few weeks ago the keypad second row from the bottom (RST/BST/SST/X<>Y/SUM+/1/2/3/-) stops functioning.

Have you got any idea it is easily reparable?

How to dismantle this unit? ("To open the case it is enough to remove one single screw from the back cover." - is it same for TI-65? Where is that screw?)

Thank you!
Csaba
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12-17-2017, 12:05 PM
Post: #22
RE: Texas TI-66 Programmable: Toshiba skills to rescue Texas...
(12-17-2017 02:45 AM)rprosperi Wrote:  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.

Thanks for the offer, Bob. Much appreciated.

I've not actually taken an oscilloscope to the machine yet but the corroded bits are clearly the first things to sort out.

I found a new RAM chip from a seller in London and I'll probably have it in the New Year.
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12-17-2017, 12:22 PM (This post was last modified: 12-17-2017 12:22 PM by grsbanks.)
Post: #23
RE: Texas TI-66 Programmable: Toshiba skills to rescue Texas...
(12-17-2017 08:29 AM)Csaba Tizedes Wrote:  I have a TI-65 in a very good shape and working condition, but on the LCD some annunciators and the segments of exponent display don't lit. And few weeks ago the keypad second row from the bottom (RST/BST/SST/X<>Y/SUM+/1/2/3/-) stops functioning.

Have you got any idea it is easily reparable?

The TI-65 is a machine that I don't know at all. Actually, its architecture is completely different from the TI-66. For one thing, it's a TI device (as in made by TI) with a flexi-PCB and a couple of TI processors that work in a master-slave configuration. I'm guessing one of the CPUs manages the display and the keypad while the other does the actual calculations. The TI-66 is Toshiba-made.

Does the display blank when you press a key? If so, that's usually a reasonable indication that the same CPU is handling both.

It could be corrosion. That was pretty common for those machines that ran on a pair of LR44 button cells. If so then you might be in time to fix things given that the problems only started recently.

Looking at a picture of the machine's innards (see http://www.datamath.org/Sci/Galaxy/TI-65.htm), I don't see a screwhole so I suspect the case is held together purely with clips. In fact TI seem to have gone down the screwless route with this calculator as I see that the LCD is held on with heat-stakes, making dismantling that part extremely unadviseable.

Not an easy one here!
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12-18-2017, 09:14 AM
Post: #24
RE: Texas TI-66 Programmable: Toshiba skills to rescue Texas...
It would be great if the ROM could be dumped from this calculator ...

http://www.hrastprogrammer.com/hrastwerk/
http://hrastprogrammer.bandcamp.com/
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