I found this guy had the same problem I am having now but unfortunately, he had no solution so I'm hoping folks on this forum can help:

https://www.youtube.com/watch?v=jX0eC26vEVA

Problem: Turning the key switch to the right/clockwise ('on') and then turning the power button on doesn't seem to reset the machine. I was able to set the odds 1x and All the lights turned on (not just the bottom half of the machine) and the red LED lights on the motherboard were all on indicating it was running correctly.

What I've done so far:
-checked that there's enough tokens in the hopper
-checked fuses (seems to be a-ok)
-checked for any loose connections in wiring.. especially to the power (seems to be a-ok)
-tried pressing the 'reset' button located next to the key switch while turning the power on
-tried turning the door key to the left (instead of the right which opens the door)
-tried moving the two black switches beneath the key switch in the opposite setting - nothing.

No number (1-6) nor specific error code (i.e. E1) ever appears... in this machine's case usually in the Credit area of the game. Turning the reset key switch has no effect and the video monitor simply spits out "Communication Error. Please wait." and that's about it. Here are a few pictures.

IMG_5618_ErrorMessage1.jpgIMG_5617_ErrorMessage2.jpgIMG_5614_Azteca_The_Legend_Returns.jpgIMG_5612_Key.jpg

Do I have a dead motherboard? I couldn't find a "battery" only a capacitor. Does anyone know if it needs a new battery? If so, what does that look like?

Can anyone help me?