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Episode 39 - Arcing

For Amusement Only EM and Bingo Pinball Podcast·podcast_episode·10m 13s·analyzed·Apr 19, 2015

Analysis

claude-haiku-4-5-20251001 · $0.014

TL;DR

EM pinball switch arcing: when it's normal, how to diagnose, and repair techniques.

Summary

Nicholas Backbone discusses switch arcing in electromechanical pinball machines, answering a listener question about AC coil wiring polarity and then explaining when arcing is normal vs. problematic. He covers diagnosis techniques, remediation methods (filing and burnishing contacts), and specific switch types prone to arcing, using a personal anecdote about carbon arc movie projectors for context.

Key Claims

On AC coils in early EMs, wiring polarity doesn't matter; it only matters if a diode is attached (DC coils in later EMs)
high confidence · Nicholas Backbone, response to Don's listener question about 1969 Gottlieb Target Pool
Flipper end-of-stroke switches will arc and it's nearly impossible to eliminate all arcing if the switch carries high current load
high confidence · Nicholas Backbone, main segment on arcing
Score motor contacts should not arc; arcing on score motors is undesirable and usually indicates a problem needing repair
high confidence · Nicholas Backbone, distinguishing high-current vs. normal-current switches
When filing switch contacts, file the flat face (not the pointed face) and check frequently to avoid over-filing
high confidence · Nicholas Backbone, remediation technique explanation
Plastic-sheathed wiring (vs. cloth-sheathed) indicates 120-volt high-voltage circuits
high confidence · Nicholas Backbone, recap of high-voltage identification from prior episode

Notable Quotes

“On an AC coil, it doesn't matter at all. The only thing to watch out for is later EMs where they started mixing in DC. If a coil has a diode attached, it will matter.”
Nicholas Backbone @ ~2:00 — Direct technical answer to listener question clarifying AC vs. DC coil wiring
“If the switch contact carries a high current load, it's almost impossible to eliminate all arcing.”
Nicholas Backbone @ ~3:30 — Core principle establishing when arcing is normal vs. problematic
“You can file the contacts until they are smooth and shiny, but it won't make one bit of difference.”
Nicholas Backbone @ ~3:45 — Explains the futility of filing high-current switch contacts like flipper end-of-stroke switches
“Arcing exacerbates the original problem, which was a dirty switch... the little mini explosion that takes place as the switch contacts come apart causes damage to the contacts themselves.”
Nicholas Backbone @ ~7:00 — Explains the feedback loop between arcing and contact degradation
“Be careful. You can get hurt easily.”
Nicholas Backbone @ ~13:30 — Safety warning about high-voltage circuits (120V in plastic-sheathed wiring)

Entities

Nicholas BackbonepersonDonperson Gottliebcompany Harry Williamsperson Target PoolgameFor Amusement Onlyorganization

Transcript

groq_whisper · $0.031

0:00

What's that sound? It's For Amusement Only, the EM and Bingo Pinball Podcast. Welcome back to For Amusement Only. This is Nick Baldridge. Before we get started on today's topic, I wanted to pay some special attention to a listener email that I received today. It's from a listener named Don, who asks, I'm currently working on a 1969 Gottlieb Target Pool. I was listening to your episode about flippers and the wiring aspect piqued my attention. I know it matters which way a flipper coil is wired, but does it matter which way a two-lug AC coil for pops, slings, score reels, or etc. is wired? I'm thinking not, but just wanted to ask you. Enjoying the show. Thanks, Don.

0:49

Well, I answered Don privately, but I asked if I could read this on the air because it's a great question.

0:57

So, this is one of those things I'm surprised that I glossed over, but it won't be the last, I'm sure.

1:06

The answer is that on an AC coil, it doesn't matter at all. The only thing to watch out for is in later EMs where they started mixing in DC, if a coil has a diode attached, it will matter.

1:24

However, on the earlier EMs, where everything is run from pure AC, it doesn't matter one bit. Other items, like flippers, as Don mentions, matter greatly, mainly in the end-to-stroke switch that's wired in parallel to the flipper.

1:46

Thanks, Don, for the question, and I hope this helps someone else as well. Today's topic is arcing, and this will be another brief one. I'm completely consistent in my inconsistency here. But switch arcing can either be a problem or normal behavior.

2:08

And the way that you determine if it's a problem is if the switch contact carries a high current load, it's almost impossible to eliminate all arcing. For example, cabinet flipper switches,

2:27

unless they have a capacitor and end switches on flippers Both of those positions tend to arc and there not a whole lot you can do about it You can file the contacts until they are smooth and shiny, but it won't make one bit of difference. On other contacts, for example, a score motor contact, arcing is not desirable, and usually not a good thing.

3:02

Not that arcing is ever a good thing, but in a score motor's case, you really don't want arcing if you can avoid it.

3:11

There are very few contacts on a score motor which have that high current load normally reserved for one or possibly two switch pairs. so part of the issue with arcing is it can be hard to determine if a switch is actually arcing. So one technique is to turn off all the lights and observe as the switch in question is being used if there's arcing involved. If there is then the contact needs to be burnished or filed and the switch readjusted, and then check again. Unfortunately, it's a bit of trial and error, because the arcing exacerbates the original problem, which was a dirty switch.

4:04

So the switches need to be cleaned, but due to the arcing, the switch contacts have become pitted. the little mini explosion that takes place as the switch contacts come apart causes damage to the contacts themselves.

4:23

So in your filing, you have to make sure that the switch itself, the face, is actually flat. And this is on the flat face. So if you have a pointed face and a flat face, you don't want to file the pointed face. You just want to clean or burnish those contacts. The flat face is the one that is typically damaged and needs to be filed flat.

4:51

This also happens on switches where there are two flat faces which touch each other. And in that instance both faces need to be filed until they both flat sometimes the only way to do this appropriately if you don have a nice extending lighted mirror which I don is to take the switch stack apart This can be difficult

5:18

and so in certain cases what I will do is take the switch stack off of the cam or motor where it's causing the problem, examine it in the cold light of the day as far as I can, and then squeeze the contacts closed and file them both at the same time, checking my work fairly frequently to make sure that I'm not over-filing. You don't want to file more than is absolutely necessary, because those contacts will have a limited lifespan. Even if your machine is running flawlessly, you want to check for arcing every so often and make sure to clean.

6:01

This is not something that should recur with any frequency unless it's one of those contacts that carries a high current load. So to review, switches with a high current load would be end-of-stroke switches on flippers. This includes the impulse flippers from the early days, 40s and 50s Williams, as well as all more modern EMs flippers. reset or start relays typically have that higher voltage running through them, which allows for a higher current to flow.

6:44

And one way to tell quickly, to recap my high voltage episode, is if the wire is plastic sheathed instead of cloth sheathed, it carries 120 volts.

7:00

Again, you don't want to be messing with that stuff while the machine is on. be careful. You can get hurt easily. So, one thing of interest, I worked for several years at a movie theater, and it was one of the last movie theaters in America that ran carbon arc projectors. Now this was a method used to light the frame which was popular in the days before say the 1970s And the interesting thing about this is that it an intentional arc

7:44

It's an open flame, basically. So you have an incredibly high direct current running through both the cathode and the anode of this carbon arc. That's a term that's used also in diodes. you strike them together, you just touch them on their faces not with your hands, obviously there was machinery involved and then spread them apart and there's an open flame that's generated and that is what lights the screen.

8:17

Now you'd have to change these carbon rods every so often a couple times a night typically if we ran two showings and towards the end the quality of these carbon rods started to degrade quickly it seemed like there was more air getting inserted into them occasionally the rods themselves the arc would just go out, it would splutter out and die and that was pretty terrible because everyone in the movie theater goes hey, what's going on? so the only way to fix that of course is to re-strike the arc and get that flame going again so arcing in a pinball machine always reminds me of that it's just one of those things that's tied up in my brain and probably always will be but while I was there towards the end of my tenure They switched from those carbon arc lamphouses to xenon bulbs.

9:22

And xenon is a pressurized gas and would light just by flipping a switch, similar to a fluorescent tube, but very, very high voltage again.

9:38

So anyway, all that said, arcing is typically pretty bad. Thanks for listening. My name again is Nick Baldridge. You can reach me at 4amusementonlypodcast at gmail.com. You can find us online at 4amusementonly.libsyn.com. And you can listen to us on iTunes, Stitcher, Pocket Casts, via RSS, on our website, and also on Facebook. Thank you again for listening, and I'll talk to you next time.