TEXAS TI-74 BASICALC & 8K RAM Cartridge teardown

[jebem]

Texas TI-74 8KByte RAM constant memory removable cartridge details.

The constant memory cartridges housing a HM6264 8KByte CMOS SRAM memory uses a 3-Volt Lithium battery able to retain data up to 5 years when removed from the console, according to the Texas official documentation.

Well, after all these years, for sure the internal memory battery backup was depleted, and it may have contributed to the cheap IKEA batteries depletion and leaking.



The year is 2016. This Texas TI-74 8K RAM Cartridge internal details are about non existent. So it was time for a Texas TI-74 8K RAM removable cartridge total teardown.

This small box sports a sturdy and solid build.
Having no visible screws I decided to remove the metal plate. To make this task easier I have used a hot air drier to soften the glue a little and a x-acto knife to lift the metal plate.

A small metal spring is used to connect the internal shield to the external metal plate.
This is important as this metal plate is connected to the TI-74 calculator internal shield when the cartridge is inserted to comply with radio frequency regulations.

The 30-pin external cartridge port interface protocol is very well documented in the publicly available Texas TI-74 Technical Data Manual.
Get one copy while it still is available.



After removing the plastic label looking for screws, I had no luck.
So the only way was to force the cover to lift a little on both sides of the case.
In this particular case, the best choice for this job was to use a large screwdriver applying a little twisting force at the slot one side at a time.

The cover started to lift and came out easily, although the four cover latches were destroyed in the process. This was caused by the very rigid case that was not flexing at all to allow a cleaner job.

The PCB assembly is totally shielded by a tin plated aluminum foil.



(to be continued)