# Episode 57 - Rectifiers **Source:** For Amusement Only EM and Bingo Pinball Podcast **Type:** podcast_episode **Published:** 2015-05-07 **Duration:** 12m 40s **Beat:** Pinball **URL:** https://foramusementonly.libsyn.com/episode-57-rectifiers --- ## Analysis Nick Baldridge provides a technical deep-dive into bridge rectifiers in pinball machines, explaining how they convert AC power to DC voltage. The episode covers rectifier theory, historical context (from selenium rectifiers in early Genco machines to modern silicon versions), and practical maintenance considerations for collectors and operators. ### Key Claims - [HIGH] Most games manufactured in the later EM era and some early games used bridge rectifiers to convert AC wall power to DC power — _Nick Baldridge, host, opening segment_ - [HIGH] Genco was fond of using rectifiers in their early machines, years before Williams, Bally, and Gottlieb regularly used them in late EMs — _Nick Baldridge, mid-episode discussion of manufacturer adoption_ - [HIGH] Early 1930s pinball machines used dry cell batteries to power electrical components, and these batteries were incredibly heavy, similar to or heavier than car batteries — _Nick Baldridge, historical section on early electrified machines_ - [HIGH] Selenium rectifiers, used by Genco in the 30s-50s, increase resistance over time and produce a bad smell; replacement with silicon bridge rectifiers is usually recommended — _Nick Baldridge, selenium vs. silicon comparison section_ - [HIGH] DC power to a coil provides consistent pulse strength, whereas AC power varies depending on the phase and timing of the cycle when the switch closes — _Nick Baldridge, explanation of why later EMs used DC rectification_ ### Notable Quotes > "Most any game manufactured in the later EM era, as well as some really interesting early games, used what are known as bridge rectifiers to convert the AC power that comes out of the wall into DC power." > — **Nick Baldridge**, Opening segment > _Core thesis statement establishing the scope of the episode_ > "A bridge rectifier is a set of four diodes, which are arranged in a particular order." > — **Nick Baldridge**, Mid-episode technical section > _Definition of bridge rectifier structure_ > "If you have DC power going to a coil, it will always pulse at the same strength. Now, if you have AC going to a coil, for example, a pop bumper in an earlier EM, depending on the phase and time of the cycle, when you happen to close that switch, it's going to provide more or less power than it would if you hit it right in the center of the cycle." > — **Nick Baldridge**, Advantage of DC power section > _Explains the performance benefit of rectification in EM machines_ > "Dry cell batteries would drive all of the electrical components on these early pinball machines. If you were to take one of those early pinball machines and convert it to wall power today which can be advisable or you can run those early pins off of a 12 volt battery like you might use in a lawnmower or similar." > — **Nick Baldridge**, Early machine power conversion section > _Practical restoration guidance for early pinball machines_ > "Silicon at the time, in the 30s, 40s, 50s, there was no such thing. So what Genco did is they used something called a selenium rectifier." > — **Nick Baldridge**, Selenium rectifier history section > _Historical context for rectifier technology evolution_ > "Selenium rectifiers over time do a similar thing. Over time they increase the resistance in the circuit and start stinking heavily." > — **Nick Baldridge**, Aging rectifier problems section > _Key maintenance concern for collectors with older machines_ ### Entities | Name | Type | Context | |------|------|---------| | Nick Baldridge | person | Host of For Amusement Only EM and Bingo Pinball Podcast; content creator focused on EM and early pinball technical topics | | For Amusement Only | organization | Podcast focused on EM and Bingo pinball machines | | Genco | company | Early pinball manufacturer; pioneered use of rectifiers in their machines, including selenium rectifiers in 1930s-1950s | | Williams | company | Major pinball manufacturer; adopted rectifiers regularly in late EM era | | Bally | company | Major pinball manufacturer; adopted rectifiers regularly in late EM era | | Gottlieb | company | Major pinball manufacturer; adopted rectifiers regularly in late EM era | ### Topics - **Primary:** Bridge rectifier technology and operation, AC to DC power conversion in pinball machines, EM era machine electrical systems, Selenium vs. silicon rectifiers: aging and maintenance - **Secondary:** Early pinball machine power sources (dry cell batteries), Restoration and conversion of early machines to modern power, Manufacturer history (Genco, Williams, Bally, Gottlieb) ### Sentiment **Neutral** (0.5) — Educational and technical tone; host is informative and engaged but not promoting any particular product, company, or viewpoint. Content is objective and matter-of-fact. ### Signals - **[content_signal]** Long-form technical education episode focused on EM pinball electrical systems; positions For Amusement Only as an authoritative source on classic pinball maintenance and theory (confidence: high) — Entire episode structure and delivery; host deep knowledge of rectifier technology and historical context - **[restoration_signal]** Practical guidance on identifying, maintaining, and upgrading rectifier systems in early and late EM machines, including selenium-to-silicon conversion recommendations (confidence: high) — Detailed sections on selenium rectifier aging, replacement recommendations, and conversion procedures for machines running on wall power vs. battery - **[historical_signal]** Documentation of rectifier technology adoption timeline: Genco's early use in 1930s-1950s, Williams/Bally/Gottlieb in late EM era; transition from selenium to silicon technology (confidence: high) — Genco was using rectifiers before major manufacturers; selenium rectifiers were used in 30s-50s; silicon rectifiers represent modern replacement - **[design_philosophy]** Explanation of why later EM designers chose DC rectification over AC: DC provides consistent solenoid pulse strength, improving game responsiveness and snappiness compared to AC phase-dependent power delivery (confidence: high) — Direct comparison of DC vs. AC solenoid behavior; late EMs adopted rectifiers to achieve crisp, reliable coil operation - **[technology_signal]** Discussion of aging rectifier failures, heat generation, and odor as reliability indicators in vintage machines; silicon superiority for heat reduction and safety (confidence: high) — Selenium rectifiers increase resistance and smell over time; silicon rectifiers produce less heat and are safer; both can fail --- ## Transcript 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. I've been working on some really super irritating solid state problems here in the past couple days. So, because rectifiers are top of mind, I thought I would take today's show to talk about bridge rectifiers. Most any game manufactured in the later EM era, as well as some really interesting early games, used what are known as bridge rectifiers to convert the AC power that comes out of the wall into DC power. So in order to explain the way that a rectifier works, it's important to know some of the theory of what comes out of your wall. Buckle up, because this is going to be super technical. No, not really. I'm going to keep it pretty straightforward. So what comes out of your wall is what's called a sine wave. And a sine wave differs from the median, so the middle level, by a certain amount above and below. So 60 times a second, the current is alternating between positive and negative. This allows most things that run off of AC to work just fine. Light bulbs, for example, are AC devices. They require no rectification to run. Some devices require a transformer in order to step up or step down the voltage. But we're not talking about transformers today. We're talking about rectifiers. Rectifiers take each half of that sine wave that differs from the mean and smooth it out. There are two kinds of rectifiers. There's half-wave and full-wave. Sorry if you can hear that over the air conditioner. Someone was just flying overhead. So, half-wave rectification just smooths out the negative side of the cycle, typically. That's not really useful for our setup, though, for pinball. What you typically want is full wave rectification. What this does is it converts the AC completely to DC. Now, here's a secret. Once it's converted to DC, it's not truly DC. There is, in the signal, something called ripple. this ripple exists as tiny little bumps above or below that median that middle line If you're dealing with a computer like a solid state system, you want that ripple to disappear completely. If you're dealing with something like a flipper, for example, a pop bumper, some kind of solenoid in an EM, then a little bit of ripple is not going to hurt anything. To smooth out the ripple, what you can do is add a capacitor to the output. Now it's important to note what a rectifier is, and in this case we're talking about a bridge rectifier, which is full wave rectification. A bridge rectifier is a set of four diodes, which are arranged in a particular order. The way a diode works is that it blocks current flow in one direction up to a certain point, and if you overload it, it will just open up and start allowing current in both directions. But normally, the way that it works is that it stops the current from flowing from the anode to the cathode. The cathode is the banded side of the diode. Current always flows from the cathode to the anode. Unless, of course, you're talking about a Zener diode, but that's a totally different subject. Anyway, I'm starting to get too technical, so let me back it up. A bridge rectifier is used to allow for single voltage operation of a coil or other device in a pinball machine. If you have DC power going to a coil, it will always pulse at the same strength. Now, if you have AC going to a coil, for example, a pop bumper in an earlier EM, depending on the phase and time of the cycle, when you happen to close that switch, it's going to provide more or less power than it would if you hit it right in the center of the cycle. So the idea with later EMs was to make them a bit snappier, and DC power does allow for this. In earlier EMs, we're talking much earlier, early wood rails, Genco was fond of using them in order to drive their coils. This is years and years and years before Williams, Bally, Gottlieb started using them regularly for their late EMs. EMs And I mentioned this before but if you think about it any of the early pins from the 1930s which used electric power to drive coils or change scores on a light board or allow bumpers to function worked off of dry cell batteries Dry cell batteries are incredibly heavy. they're similar in heft to a car battery but even heavier than that typically. So these dry cell batteries would drive all of the electrical components on these early pinball machines. If you were to take one of those early pinball machines and convert it to wall power today which can be advisable or you can run those early pins off of a 12 volt battery like you might use in a lawnmower or similar. But if you run them off of wall power you'll need to rectify the power coming from the wall and convert it to DC. The DC output should match what the dry cell battery had. Again it's typically 12 volts and once you do this you'll have reliable crisp operation of your early pinball machine for some time in the future now genco when they were doing this in the early days used a rectifier that wasn't made out of silicon Silicon at the time, in the 30s, 40s, 50s, there was no such thing. So what Genco did is they used something called a selenium rectifier. Selenium rectifiers are pieces of metal arranged in a particular way that do the same thing. If you're familiar with arcade games, early arcade games, and some early solid-state pinball machines, they used something called a linear power supply. Now, these linear power supplies, over time, don't do a good job of providing adequate power and need components replaced and so forth. These selenium rectifiers over time do a similar thing. Over time they increase the resistance in the circuit and start stinking heavily. So replacement with a silicon bridge rectifier is usually desired. Some rectifiers are cool looking and they add to the heft of the game, so especially in an early wood rail I wouldn necessarily remove it although there are some that like to do that None of my games have a selenium rectifier but if they did I would preemptively replace the selenium rectifier with a silicon rectifier. It won't necessarily have any long-lasting ill effects to run it until the rectifier dies. But those rectifiers have provided years and years and years of service, and it's probably time for them to retire. They've done a good job, but in this case, it would make sense to replace them. Uh, silicon rectifiers are less dangerous because they produce less heat and, uh, they don't produce that horrible smell. Uh, they just produce smoke if you blow them up. So, um, in conclusion for this incredibly, um, exciting episode of For Amusement Only, I wanted to talk a bit, again, about this movie theater that I worked in as a teenager. The projectors required DC power in order to strike those carbon arcs together. Strike the carbon rods together and generate the arc. There we go. those rectifiers were massive. They took up an entire floor's worth of space. Basically, you'd have the projection booth, which had the projectors in it, and then the entire space underneath of it, taller than the size of a full-grown person, was filled floor to ceiling with these rectifier units. This theater was built in 1928, and the rectification technology, obviously quite a bit different in the 1920s than it is today. I've never seen a modern movie theater and how it's rectified, but I have to assume that it uses some form of silicon rectifier. it's really neat when the projectors are on the rectifiers hum incredibly loudly but they do the job a bit differently so thank you again for joining me my name again is Nicholas Baldridge you can reach me at 4amusementonlypodcast at gmail.com and you can find us online at foramusementonly.libsyn.com You can listen to us on iTunes, Stitcher, Pocket Cast, via RSS, on our website, and on Facebook. Thanks again for listening, and I'll talk to you next time. _(Acquisition: groq_whisper, Enrichment: v3)_ --- *Exported from Journalist Tool on 2026-04-13 | Item ID: 1095993d-9fc3-4e76-b9ba-caecdb0cb19e*