Hello Aiken Drum,
WOW! Absolutely Amazing!!

clear, step by step instructions. I followed the same and revived my TomTom Go750.

I have internal memory and a sd-card, I have to copy the cal.txt in both the places, if I remove cal.txt then the calibration goes back to old status. This means, we need to keep cal.txt file all the time and TomTom will read it every reset.

I can live with this.
Thank you, Thank you and Thank you.

Best regards
Sid