Episode 78 - Backdoor Bingo Oddity

For Amusement Only EM and Bingo Pinball Podcast·podcast_episode·8m 19s·analyzed·May 28, 2015

Analysis

claude-haiku-4-5-20251001 · $0.016

TL;DR

EM bingo back-door interlock switch decoded: disables counters, not tilt.

Summary

Nick Baldridge explores the mechanical locks and security features on bingo pinball machines, focusing on an unusual switch on the back door that he initially believed was a slam tilt switch but later discovered, with help from Jim Willing of Spooky Pinball's EM Dungeon, actually disables coin and play counters during maintenance to prevent false credit registration.

Key Claims

Early bingo machines from United (late 1940s, early 1950s) used removable wooden doors, similar to wood rail pinballs of that era
high confidence · Nick Baldridge, opening discussion of door evolution
The transition from removable to hinged doors was significant because it prevented damage from technicians dropping or stepping on detached doors during coin collection
high confidence · Nick Baldridge, design history explanation
Bingo machines have back glass held in by two thin rail locks with spinning receivers (not traditional tongue-and-latch mechanisms)
high confidence · Nick Baldridge, technical description of back glass locks
Back door locks on bingo machines have large rectangular lock tongues/tines that actuate a switch
high confidence · Nick Baldridge, describing the unusual back door lock mechanism
EM pinball machines lack software/hardware interlocks that disable high voltage when doors are open
high confidence · Nick Baldridge, discussing safety design philosophy differences
The oddly-shaped switch on bingo back doors disables coin counters and play counters during maintenance, preventing false credit/replay registration
high confidence · Nick Baldridge, citing information provided by Jim Willing from Spooky Pinball's EM Dungeon
Nick Baldridge has a bingo machine (Ticker Tape) with the original lock plate still in place, but may have the counter-disabling switch misadjusted
high confidence · Nick Baldridge, personal machine inventory and troubleshooting notes

Notable Quotes

“It was a big deal when companies started moving toward hinged doors, as it allowed you to leave the door on the game, preventing damage, you know, because you're going in there to do your collections.”
Nick Baldridge @ ~0:45 — Explains the practical engineering rationale for a key design evolution in EM bingo machines
“one of the things that makes EM repair exciting, shall we say, is that there is no concept of an interlock. So, the software in the machine, or the hardware, does not disable high voltage lines just because you have a door open, typically.”
Nick Baldridge @ ~2:30 — Highlights a fundamental safety difference between EM and modern pinball design philosophy
“If you're a technician and you're working on a bingo, you open up the back box and you start fooling around with the internals, stepping things up and racking up credits where you wouldn't normally. We wouldn't want those to register as part of your earnings.”
Nick Baldridge @ ~2:50 — Explains the practical purpose of the counter-disabling interlock in protecting operational integrity
“Jim was nice enough to email me back and say, nope, it's actually something completely different.”
Nick Baldridge @ ~3:45 — Acknowledges correction from Jim Willing and community knowledge-sharing

Entities

Nick BaldridgepersonJim WillingpersonFor Amusement OnlyorganizationSpooky PinballcompanyUnitedcompanyMagic Screen BingogameMystic Lion BingogameTicker TapegameEM Dungeonorganization

Signals

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design_innovation: Counter-disabling interlock switch on bingo back doors that prevents false credit/replay registration during technician maintenance—a clever workaround to the lack of electrical safety interlocks in EM machines
high · Nick's detailed explanation of the switch function and Jim Willing's technical confirmation
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restoration_signal: Clarification of bingo machine back door lock construction and function; important for proper restoration and maintenance of original components
high · Technical breakdown of thin rail locks on back glass vs. rectangular tongue locks on back door
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historical_signal: Documentation of the engineering transition from removable wooden doors (United, late 1940s-50s) to hinged doors, driven by practical durability concerns during coin collection
high · Nick's detailed account of early bingo design compared to wood rail pinball contemporaries
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community_signal: EM community experts (Nick Baldridge and Jim Willing) actively sharing technical corrections and deepening collective understanding of obscure machine functions
high · Jim Willing's email correction to Nick; Nick's public acknowledgment and gratitude

Topics

EM/Bingo machine mechanical locks and door hardwareprimaryCounter-disabling interlock switches on bingo machinesprimaryDesign evolution from removable to hinged doorsprimarySafety and interlock design in EM vs. modern pinballsecondaryEM machine restoration and maintenance practicessecondaryCommunity knowledge-sharing and technical collaborationsecondaryHistorical pinball manufacturing (United, late 1940s-1950s era)mentioned

Sentiment

positive(0.85)— Educational, appreciative tone throughout. Nick expresses genuine curiosity and thanks Jim Willing for the correction. No negative sentiment about manufacturers or design choices; framed as historical/technical interest rather than criticism.

Transcript

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What's that sound? It's For Amusement Only, the EM and Bingo Pinball Podcast. Welcome back to For Amusement Only. This is Nicholas Baldridge. There are several different locks on any given bingo. And depending on the era and manufacturer, there are going to be various additional locks. So I believe I've mentioned before about the coin box lock. In the very earliest bingos, especially from United, they used a removable wooden door. This is very similar to wood rail pinballs of the period. the late 40s, early 50s, would also use removable doors. It was a big deal when companies started moving toward hinged doors, as it allowed you to leave the door on the game, preventing damage, you know, because you're going in there to do your collections. who knows what happens. Someone stomps on the door while you have it set down. Maybe you drop it. There's all kinds of different things that could happen. So if you have it on a hinge, that's all the better. Now in the backbox, you have four different locks. You have two, which hold the back glass in. And these are thin rails, which have a lock that actually spins in a receiver inside the head. There not a traditional tongue sticking out of the lock latching it into place In the backbox, there are two additional locks which hold the back door closed. These locks do have a tongue. However, they are large and rectangular instead of the typical curved metal that most are familiar with today. these large rectangular lock tongues, or tines, or however you want to describe them, both sealed up and latched into receivers in the edge of the backbox, But they also, at least in one instance, actuate a switch. Now what this switch did was a topic of minor debate. Jim Willing from the Spooky Pinball Podcast's EM Dungeon segment, which you should give a listen to if you haven't, emailed me the other day and asked if I knew what that switch was for. and I assumed he was talking about that particular switch, which is oddly shaped and in an odd position. And I had always assumed that it was part of the tilt system and acted as an odd slam switch. It's right beside the search relays on the back door, on a Magic Screen Bingo or a Mystic Lion Bingo So the placement would make sense You wouldn want someone wrapping on the door in such a fashion that they were able to make these relays jump and connect. At least that was the thinking that I had. But as it turns out, it's more complicated than that, and also kind of fascinating. So, one of the things that makes EM repair exciting, shall we say, is that there is no concept of an interlock. So, the software in the machine, or the hardware, does not disable high voltage lines just because you have a door open, typically. the closest that anything comes is in a bingo an additional light right inside the front door lights when you open the front door but that's about it so there exists on the bingo this odd shaped switch on the back of the door and that is an interlock, but what it's disabling is not high voltage circuits. It's disabling the coin counters and the play counters. So if you're a technician and you're working on a bingo, you open up the backbox and you start fooling around with the internals, stepping things up and racking up credits where you wouldn't normally. We wouldn't want those to register as part of your earnings. And you wouldn want them to register as part of your total plays either total replays So basically this just disables the coin counter and the total replays counter. It's pretty cool. Now, I didn't happen to be in front of a schematic at the time, so I just said, I think that's a slam switch. And Jim was nice enough to email me back and say, nope, it's actually something completely different. So I wanted to say thank you to Jim for that info, and it's always interesting to figure out what something like that is actually doing. Now, on my machines, I typically have an aftermarket lock in that position. The only one which has the original lock plate is ticker tape. And again, I've always assumed that that was part of the tilt circuit, so I've never really messed with it. I've never had a situation where I needed to verify that the tilts were working, but now that I know what that actually does, I'm curious to know if my meters are actually ticking up as they're supposed to. I may have the switch misadjusted so that it's always closed. I'm not sure. so that's it for tonight's curiosity corner thank you again for joining me my name again is Nicholas Baldridge you can reach me at 4amusementonlypodcast at gmail.com and you can listen to us on iTunes Stitcher Pocket Casts via RSS on Facebook, on Twitter and on our website which is 4amusementonly.libsyn.com thanks again for listening and I'll talk to you next time