Posted in Fall 1994, there is a service modification Williams is suggesting to be done to the Eddy Boards on the Next Generation pinball. SB64 states: Sensor creating False Switch Readings. This is related to a functioning (not a broken Eddy Board). States there is a condition which can exist when the Eddy Sensor is closed, and any opto switch on the same related switch row might change the state. This will add confusion in the game play it appears. The solution is to a board trace and add a 1N4148 diode. Has anyone seen this or done this??? Has anyone experienced the problem? I am completely restored a Next Generation machine, and doing a deep dive to make the machine perfect. Please share your thoughts and ideas. Eric

eddy 1 (resized).jpg

eddy 2 (resized).jpg

Interesting thing, AFTER finding this service mod, and getting confused my boards were not looking like there service diagram, I looked up my board numbers. The boards SEEM to be from a Twilight Zone and don't match the A-16922 number out of the STTNG Manual. I guess I will look up the T Zone and see if they did a mod on that board.

Can you tell by looking at these photos, if this board needs the modification Williams is describing? Appreciate your help. This appears to be a different board than in the Service Bulletin, and I couldn't find anything about needing the modification when looking into the TZ Service Bulletins. My OCD is driving me crazy on this.

DSC02423 (resized).JPG

DSC02425 (resized).JPG

DSC02426 (resized).JPG

DSC02427 (resized).JPG

Agree with you. I see Q3 on that board, and mine doesn't have one. So somewhere along the way, somebody swapped out (2) of the boards in my STTNG with TZ board. My boards work in the machine. I place the ball over the sensor, and check the switch edges, and confirm operation.

SO. my next question may not matter. Does the machine NEED the original boards to work, or since the TZ boards are in there, and the electrical design is different, there isn't any issue to fix??

thank you by the way for the follow up information
Eric

wow, I think you deserve a degree with all this amazing detective work. The entire reason I brought this topic up, is because I am rebuilding a STTNG almost from the ground up. And as you all know, this machine lives or dies with how the optos work. Since the original fix in the service manual determines there
"could" be a problem, my OCD kicked in thinking there was a "fix" needed. As one person wrote, there has been multiple versions of a board which do the same task. Why there are multiple versions is beyond me.

Can't thank you enough for your sherlock Holmes work to shed needed life on this issue. Having had this machine once before, I know how flaky the optos "can" be. I replace ALL of the boards in the game (working or not) with all new. (16) sets AND a new version on the opto board. (that's 128 tiny solder locations). Also replaced the 7 opto trough boards with the new design.