I am not familiar with the Rancho, but possibly, was the bonus intended to reset to 0 points and then step up to 10,000 when the ball is released to the plunger lane? If so, a possible culprit might be mis-allignment of the spider arms wrt the electrical contacts, such that the machine is resetting to 10,000 and then stepping up to 20,000 ?

If so, the position of the spider arms at max bonus value may be beyond the range of electrical contacts on the board and thus showing no bonus.

I will try and take a look at the bonus units on my GP and EM Hot Tip today, to see if I can discern how they operate.

I inspected the bonus stepper on Hot Tip and Grand Prix. They were a little different, but both basically had spider arms and a circular array of 11 brass contacts. When the bonus counts down, the spider arm goes back to the first brass contact. When the ball gets ejected to the shooter lane, the spider arm moves up to the 2nd brass contact. When the bonus stepper reaches maximum bonus, the spider arm is resting on the 11th (and last) brass contact.

Can you check your bonus unit to see if it functions similarly and that the board is not misaligned such that the spider arm might be resetting to the 2nd brass contact and stepping up to the 3rd contact when the ball ejects to the shooter lane?

L

Without going back down and opening up one of my Williams EMs, I hazily recall that you will need to raise the playfield and then manually operate the plunger of the bonus reset coil until it steps back down as far as it will go. If the spider arm(s) does appear to be resting on the 2nd brass contact, then the usual way (provided nothing is bent or broken with the mechanism) was to loosen a couple fasteners on the rectangular board with the brass contacts and then actually rotate the board itself until the first contact is aligned with the spider arm. See if that makes sense?

Lee

Cool! Now you're an expert on adjusting late-70's Williams bonus steppers. Next, you need to go play some test games. LOL.