S+ Pinball Code 21

[Phan000]

Got a new machine yesterday.

Code 21,  seems to be tricky to clear.

Reels spin after startup.  Winner paid 35, then reverts to code 21.

I tried a different coin comparitor,  but no luck. 

Code P-06 on top pinball display.

[Stayouttadabunker]

Hope this helps ya?
It's from my original IGT S+ manual.
Try cleaning out the "ABC" optic holes in the encoder guide...especially the hole that lets the "A" infrared beam thu.
Probably blocked with dust or lint? (That would be the top holes, there's one on each side of the sandwiched boards.)
Check the bottom black wire on the coin comparitor harness while you're troubleshootin'.
If that one is loose or broken, that'll shoot out a code [21] too.

Click on photo below to enlarge if needed...>>>