Super Breakout paddle won't move - board problem

Vectorman

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Guys,

I'm pulling my hair out on this super breakout pcb. The paddle stays split like half all the way left, half all the way right on the screen, turning the pot does nothing.

I've checked the paddle input on the board and it's giving a smooth curve from 0V to +5V DC as the paddle control is turned, as it's supposed to. So the problem is on the board.

I've replaced literally every component on the schematic anywhere near the paddle input and the problem hasn't changed.

Where should I look?

Thanks for any guidance you can offer.

John
 
Do you have an oscilloscope?

If so, put one channel on the SENSE1 signal and the other channel on VBLANK, trigger on VBLANK. When you turn the paddle the SENSE1 signal should move relative to VBLANK. That position relative to VBLANK tells the computer where the paddle is on the screen.

If that's working right then you have to check further up the stream for issues in the NMI circuit (which taps the CPU on the shoulder to read the pot) or for bad Playfield RAM.
 
Do you have an oscilloscope?

If so, put one channel on the SENSE1 signal and the other channel on VBLANK, trigger on VBLANK. When you turn the paddle the SENSE1 signal should move relative to VBLANK. That position relative to VBLANK tells the computer where the paddle is on the screen.

Thanks for the guidance...I'll try checking that.


.... or for bad Playfield RAM.

Is this possible even if it passes the RAM test in test mode?



Thanks again,
John
 
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