hp28s need repair ?. Autotest fails

[tlfrance]

For opening, I’ve followed this article https://www.teawea.com/open-a-hp-28s-calculator/. Using a dremel it’s easy.
For the memory malfunction, i didn.t have any doubt, I could not store more than 3 rows in stack, and had some screen clear when attempting to store some var into the calculator.
For replacing the chip , i ‘ve used hot air desoldering tool. Be carrefull to protect with tape the 2 Saturn chip as they are very fragil. Solder new chip was not difficult at all.[/align]