Greetings from Phoenix Arizona! I am going to give you a summary of a problem I am having (in case you want to jump right in) and then some machine history (that may have some tips to solve the mystery)

My 1976 Williams Hot Tip (The EM Version, not the SS) intermittently bonus scores properly, but not all the time.

It scores everything in real time ok (hit a bumper, get an instant score) but after the round is over, it has a Bonus Score that a stepper wheel counts down and adds to your score. This only works intermittently. The scoring wheel works fine, just the adding of the score is not working reliably.

I think it is a coil/relay that is bad, but I can't figure out what the feature is called.

I tried to link a schematic from ipdb but the system says I am too new of a member. If you could please look it up, it is machine ID 1251.

In the picture, it is the thermometer style thing in the center of the playfield, that I am talking about. All the lights work, the stepper works, just not the scoring

Any ideas what the feature is called, or better yet, how to solve the problem?

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I am pretty excited about my machine. It is my first Pinball and my second arcade game. I bought it from a family out in the countryside. A farmer had died and the family was clearing out the barn. It turns out, there were about 6 em machines stored away in it. They playfields were separated from the backs and the legs were off, but everything was packed away.

I regret only buying one, but you live and learn.

Anyways, I searched the internet to find out what my next step should be.

After a bunch of reading and some youtube watching, I vacuumed out as much dust as I could, figured out where each wiring harness connected too and hooked it up. Much to my elation just about everything worked. I then cleaned and waxed the playfield and ordered a new ring kit.

For the most part it works reliably. It has a few quirks, but the biggest annoyance is the bonus scoring. Sometimes I have a 650,000 point game but most of the time, I have just a 78,000 point game.

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Yes, the lights go up when you should score and they step down after your round is over.

Thanks Zacaj!

I will admit I am not well versed in schematics and only understood half of what you said. (I didn't even know schematics had sections)

Then I started looking at section 20 of the schematic and now it makes a little more sense.

I printed out your reply and will take it step by step and see how it goes. I hope you don't mind if I end up asking you stupid questions along the way.

Daryl

So I looked at the switches on the scoring motor and I THINK they look ok. I did find this very badly burned coil. Could it be related? It is marked LOCK so I don't think it is, but thought I'd ask.

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After further examination I see the contact plastic part broke.
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Do you think I could plastic weld it back together, or at this point it is time to buy a new coil?

Sorry for the delay, but YES, the bonus starts at 10,000

How is the restoration/repair going? Anything else I can help you with?

Thanks Howard. I really appreciate it. I apologize for the 60 day delay, but I had almost given up on the problem and didn't realize there was a followup post.

So I looked at all the switches and made sure the stacks were good. All the wires look good and the solder connecitions look solid.

From what you highlighted, The second switch should send an electronic pulse to the 10,000 point scoring coil in the back cabinet

It seems like it is not doing that, however the rest of the resets on the second scoring wheel occur.

Does that mean there is some kind of break in the wire? Should I try to direct connect a wire from the scoring switch to the relay and see what happens?