What do you mean? Do you mean it scrolls up the screen so loosing the top part of the image leaving ‘new’ blank space (lines) at the bottom?
There are ‘system variables’ which is an area in RAN that stores information that the BASIC ROM code uses to keep track of the current state of the machine, including the position of the edit box / input line at the bottom of the normal display area. Also the current foreground (ink) and background (paper) colours are stored in this area.
My thoughts are that either there is a fault with this area of RAM (or the circuitry / wiring that feeds and controls it) or the default values from the ROM are corrupt. Although I don’t think a ROM fault is likely (they are not common faults) it’s still worth checking.
What type is the ROM chip? Is the ROM type wire link set correctly?
Mark
Standby alert 