My guess is either the unit is gunked up even though it appears not to be, or the decrement (re-set) plunger isn't getting the signal to pulse every time.

Check that the return spring is adjusted enough?

Wms reset stepper info.JPG

Here is the Williams info on them.
Assuming its not an electrical problem. And its not binding from being dirty.

Wms reset stepper.JPG

The torsion spring attaches at two points,if you remove it at the index/reset pawl [easier way]you can wind another turn.
A small pair of vise-grips is perfect for holding the spring for that.

If that one turn is too much tension you can index the spring at the gear,which depending on where you set it will be under a full turn and less.

Is this considered a difficult thing to fix?

I have a similar problem on 2 Williams machines right now and have not been able to figure it out on my own, but I am a newbie to this.

This description will be helpful in working through it, and I'll try it again before calling in the pros.

What document is this taken from, is there a Williams repair manual out there I am missing?

http://www.pinrepair.com/em/index2.htm#steps

There is a switch on this stepper which is normally made, or broken, at the reset position by a pin on the toothed wheel. What can happen is that the pin gets on the wrong side of this switch. When this happens the game will continue to show signs of apparent proper operation with the slightest defect such as you are experiencing.

I recommend you inspect this position. If you find the pin is on the wrong side loosen up the switch mount and ratchet the toothed wheel and pin to the correct side of the switch.

I can't explain how the pin gets to the wrong side but have seen it multiple times.

Keep us posted on your progress.

Mike O.
Team-EM

Me neither, if you ever figure it out let me know. I see it fairly often

--Jeff

just one little thing, It called the coin unit. The player unit looks after who is playing, the coin unit is the number of player.

When you manually operate the reset coil, does it snap back or just turns back?

Well there is the answer, it needs cleaning.
the speed that the reset coil fires, does not give much time for the return to zero of the ratchet. It should snap back, like the Ball count unit. Its not hard to clean, you do not need to un-solder anything.

Happy cleaning.

IMHO all steppers should be rebuilt when shopping an old EM out. Saves a lot of trouble down the road & they are almost always suspect.