Is my TI-58C hosed?

[jebem]

Olá Danton, como vai?

Yes, I fixed my TI-58C because luckily it was the SRAM failed chip that one can still easily find as new old stock on eBay.

Please see this:
Texas TI-58C: (in)famous constant memory issues

Good luck with your rebuild.
We do this for fun, right?

(10-01-2018 03:05 AM)DANTONVB Wrote:  

(10-24-2014 10:31 PM)jebem Wrote:  Thanks, Dave.

I have the same issue with mine.
The previous owner left the batteries inside and it leaked badly.
I have dismantled the machine piece by piece, put everything in the kitchen sink in warm water and dish soap for 15 minutes, then used a soft brush to remove the battery remains from the PCB and plastics.

Two days later I powered it on and it worked normally, except that it doesn't store in the registers or in the program steps. Just get zeros when reading.

However the current consumption is about 220mA, which seems too high for me, but I do not have another machine to compare.
Do you have a multimeter capable of reading in the 200mA region to check yours?
I would be very grateful.

A few things I have checked:

The voltages from the DC-DC power supply for the Texas IC's are fine:
Vdd = -10VDC (Pin 2 at CROM socket);
Vgg = -16VDC (Pin 1 at CROM socket);
Common point = Vss at +Vbatt. (Pin 8 at CROM socket).

Also the power supply for the TC5047AP-1 is fine:
Vdd = +4.8VDC (Pin 20);
Common point (GND at TC IC pin 8);

The large 470uF capacitor near the DC-DC power supply is a energy storage for this 5VDC SRAM IC supply, allowing the battery to be removed without losing the SRAM contents.

So my next step is to order one SRAM chip.

First, my excuses for revive an old thread, but I have the same problem as you had. Have you find an solution?

My problem:
I have a Texas Instruments TI-58C (made in Brazil). I bought this calculator new in Brazil on April 22, 1981.
It has been stored without batteries for 20 years or more. Recently I took it out to use it.

My calculator is displaying strange memory and program storage behavior. Sometimes it works as expected, but most of the time it does not store the correct number. For example, if I store the number 99.99 in a memory, it returns something like 9999000090.

Do you think you may have a damaged memory IC? My calculator has a NEC D445LC memory IC, as opposed to the common ToshibaTC5047AP-1. I think in replacing the D445LC for a ToshibaTC5047AP-1 IC. What do you think about? Or may another problem?

Thanks,

Danton
Brazil.