Main Question: How can I check a ADC0808 chip to determine if it needs to be replaced or if my issue is something else? Any advice you can offer is SO appreciated!
ADDITIONAL INFO When the arcade is in "Test Mode" (see test mode picture below for context) the output values for the X and Y axis data are not smooth and it only registers a couple of HEX values. Accordingly, it appears that the cursor\crosshair follows the behavior and moves to a different point on the screen when the HEX value changes.
X axis (VRP1X: right to left) - 0080 00C0 00E0 00F0 00F8
Y Axis (VRP1Y: top down) - 0080 00C0 00E0
(Overview) I am working on a Operation Thunderbolt arcade game. It has two guns (player 1 and 2) that use two 5v potentiometers (2 each gun) to send X and Y signals to a ADC0808 chip which appears to convert the analog signal to digital. The digital value is then used by the game to control the crosshairs of the guns on the screen.
(Issue) The crosshairs are way off in the upper right corner and they are not very responsive and jittery.
Found the schematics and found where the potentiometer signal is coming into the arcade PCB. I traced the signal to the ADC0808 chip (FYI: the chip on the board is actually a ADC0809N chip). I tested the VCC pin and it was 5v as expected. The input pins 26, 27, 28 and 1 and could see the voltage from the potentiometer within the 5v range.
I put the arcade into test mode and went to the calibration screen. I could see that the X and Y values were responding. Also, while checking voltages (see #1) i noticed that the crosshair was still not behaving correctly, but jumped to an area closer to the middle of the screen