I had a problem with a game resetting when both flippers were hit. I found the problem to be on the Rottendog power supply. This diode may be the issue, but the size is not listed on the rottendog schematic. This may be an older RD board. The diode is much larger than a diode you'd find under the playfield.

I don't believe D3 is the same size diode on the original board. So what diode do I need to replace D3 on this rottendog board? The markings I can read on the diode are "ag 40" and "8520". Thanks
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Well, I put it a working original board and the game played perfectly. So definitely on the board. I suspect this diode based on another thread I found where the issue was the diodes at D7 and D8 on an original board. I tested this diode on my board and it is testing bad. I did not disconnect it and test it yet.