7800 Control Troubleshooting - up stuck

[mtarallo]

Hi guys - I was wondering if someone on here can help me troubleshoot something - I think something fried on my 7800 - I noticed when I start a game like Xevious - the ship automatically goes up the screen - like someone is pushing up - this happens without a controller plugged into the port. It's like something is shorting pin 1 on the controller port. I checked the PCB and pin 1 from the port looks like it is going no where. There does not appear to be any burnt components - I am wondering if it is a failed diode or resistor. I appreciate your suggestions.

 

If I use an Atari 2600 game in the 7800 - the controls work as expected.

 

Thanks!

Edited November 14, 2018 by mtarallo

[+-^CrossBow^-]

That usually indicates an issue with the TIA or the RIOT chips. Controls in 7800 games behave differently on those two chips for their controls I believe as compared to the 2600. Can't remember which controls which but I believe the fire buttons are handled by the TIA so the RIOT might handle the cardinal directions.

[mtarallo]

OK great thanks - I will investigate

[mtarallo]

That usually indicates an issue with the TIA or the RIOT chips. Controls in 7800 games behave differently on those two chips for their controls I believe as compared to the 2600. Can't remember which controls which but I believe the fire buttons are handled by the TIA so the RIOT might handle the cardinal directions.

 

That was it - just replaced the

1X UM6532 IC

 

$6 fix!

 

Thank You for the advice!