trigger line troubleshooting Did I break the RIOT Chip or pop a Cap in my Sixer?

[Mr SQL]

Did I break the RIOT Chip or pop a Cap in my Sixer?

 

Left controller port Trigger line has stopped registering, but everything else on the Heavy Sixer works fine -

 

I just watched this Atari RIOT chip replacement video and have some questions -

Atari 2600 "RIOT" chip replacement - YouTube 

 

With the Heavy Sixer I see there is a Daughterboard with round caps and resistors between the Controller ports and the RIOT chip - this is missing on the Vader model in the video or integrated into the mainboard.

 

I suspect the high potentials may have fried one of these round caps and possibly not the RIOT Chip since the Heavy Sixer is otherwise working fine.

 

Section 4-27  of the Field Agent Service manual appears to suggest the Controller daughterboard and replacing these components  - 

ATARI 2600/2600A VCS Domestic Field Service Manual; FD100133, Rev.02 (robotsandcomputers.com)

 

Details on what caused the hardware fault: The left controller plug fell out of the Heavy Sixer and when I plugged it back in a large Spark jumped between my hand and the pins on the port while the Atari was powered on (freezing it) so I think the high potential overloaded a Cap or fried something in the RIOT (hopefully not, Best Electronics is fresh out).

 

[+Stephen Moss]

By trigger I assume you meant the fire button.

If so then unless your circuit is very different from those available on Atari Age the fire button is connect to pins 35 (right) & 36 (left) of the TIA, only the direction inputs go to the RIOT and so I am not sure that changing the RIOT would have any effect.

 

If you have a DMM I suggest measuring the voltages on pins pin 36 to see if it changes when the button is pressed, if it does then the TIA may be faulty. If it does not then there are several possibility's..,

Bad solder joint on controller port pullup resistor

Short Circuit on controller input port capacitor 

Bad Solder Joint on TIA pin

Bad TIA

 

On the CX2600 there is an inverter chip (7404 I think, not present to the CX2600A) between the fire pin and the TIA input, that can fail. The Diagnostic flow chart 4-27 is for a 2600 with that device fitted (2nd box down on left side of flowchart). If your model does not have that inverter then look at section 6-27 instead.   

[Mr SQL]

On 1/22/2021 at 5:34 AM, Stephen Moss said:

By trigger I assume you meant the fire button.

If so then unless your circuit is very different from those available on Atari Age the fire button is connect to pins 35 (right) & 36 (left) of the TIA, only the direction inputs go to the RIOT and so I am not sure that changing the RIOT would have any effect.

 

If you have a DMM I suggest measuring the voltages on pins pin 36 to see if it changes when the button is pressed, if it does then the TIA may be faulty. If it does not then there are several possibility's..,

Bad solder joint on controller port pullup resistor

Short Circuit on controller input port capacitor 

Bad Solder Joint on TIA pin

Bad TIA

 

On the CX2600 there is an inverter chip (7404 I think, not present to the CX2600A) between the fire pin and the TIA input, that can fail. The Diagnostic flow chart 4-27 is for a 2600 with that device fitted (2nd box down on left side of flowchart). If your model does not have that inverter then look at section 6-27 instead.   

Thanks Stephen!

I have an analog volt meter and will check the voltage change on pin 36 and I'll check the continuity while the power is off between the port and pins 35 and 36 of the TIA to rule out those other possibilities.