most 3 coin pays go thru the top two wiper fingers on reel 5, so clean/check the rivets and verify decent wiper pressure.
the exception is the cherrys. A 2 cherry win needs the top two wipers on reel 4 to be working.
the diodes complicate testing, but if you set up a two cherry win on the reels, you can pull out the reel mech and use a meter in resistance mode or diode mode to check the path from wire 92 on reel 3 to wire 15 on reel 4.
in diode mode, you should see around .6V when your +/red meter lead on wire 92 and black/com/- lead is on 15.
in ohms mode, something less than 100 ohms is typical with the probes as above.
the diodes don't often fail.
if you can post a pic of the entire front of your machine, that'd be great. Even better is emailing highest possible resolution pic to slotpics@cdyn.com (or stick them on a cloud drive someplace) and I'll add pictures to the appropriate
https://bingo.cdyn.com/slots/ folder. As many pics of the insides as you are willing to take will get posted.
is your model number 1081-something? 1081-1 paperwork is on the above site, including the reel wiring diagram (w-1041-2649-2653.png). The info I have says the reel wiring is the same for all the 1081 models. The main difference would be the index disc for reel 3 and reel tapes to get different payback percentages.