HudsonArcade
Well-known member
HYPERSPACE signal is always low and output pin L10p3 is also always low, whether the garbage on the screen or not. Grounding either didn't change anything.
However, R11p1, if this is grounded the garbage goes away, inputs to this are PHASOR' through a 470 ohm resistor and R10p10. Putting the probe on the right side of the resistor I can hear activity when I fire the phasors during a game that is associated with when I can see the faint lines of them firing on the screen otherwise that signal is always low. Which leaves the output coming from the 7518 as the only other source of the garbage I can find.
Yeah, it's probably something upstream of the PROM in that case.
Depending on the state of ALPHA, PHASOR', CIRCLE, BLANK, and MUX the PROM is disabled, and those signals get coupled to the outputs through those resistors instead.







