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Texas TI-58C: (in)famous constant memory issues
12-09-2014, 11:08 PM
Post: #5
RE: Texas TI-58C: (in)famous constant memory issues
(11-07-2014 03:45 PM)Den Belillo (Martinez Ca.) Wrote:  RE: "- CAUTION: The calculator can be damaged if the charger/adapter is connected without the battery pack installed."
About 10 years ago Joerg Woerner confirmed to me that this is true.

And I have just confirmed that my TI-58C RAM memory chip was also another victim of such irregular procedure performed by the previous owner. Details below.


Toshiba TC5047AP-1 Memory chip replacement arrived today.

After waiting for almost one month for the replacement memory chip, it finally arrived today. I am surprised to be able to find these old chips for sale in the market, so I have ordered a few, instead of keep buying additional TI-58C machines hoping to be able to find/build a working one. I like this electronics hobby after all.

[Image: ti-58C_013.jpg] [Image: ti-58C_014.jpg]


Time to extract the old defective memory chip.
I still remember the technique we used to apply to remove the TTL and MOS DIP style chips in the good old days - just use a proper cutter to remove the offending component with zero damage to the PCB.

[Image: ti-58C_015.jpg] [Image: ti-58C_016.jpg]

The underside of the memory chip reveals some nasty effects, probably caused by the high current passing thru the pins, thanks to a combination of high voltage from the power adapter used without the battery pack and the battery electrolyte leaking.

[Image: ti-58C_017.jpg]


Removing the old chip pins and prepare the PCB for the new chip.
I like this audio grade Wonder Solder by TRT (rosin flux core leaded solder). It is very easy to work with, making very good joints, and shows excellent conductivity as well.

[Image: ti-58C_018.jpg] [Image: ti-58C_019.jpg]

Time to insert the new memory chip and assemble the machine.
As I do not like the keys to jingle in the slots, I have applied a new thicker foam as well.

[Image: ti-58C_020.jpg] [Image: ti-58C_021.jpg] [Image: ti-58C_022.jpg]


Testing time....

I was rewarded with a working machine. It can store data and programs once again!




Jose Mesquita
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RE: Texas TI-58C: (in)famous constant memory issues - jebem - 12-09-2014 11:08 PM



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