Audio amplifier "hums" due to design flaw: can it be fixed? - Page 1
Forum section: electronics / projects

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 24, 2017, 06:50:04 pm
content: Classic Nintendo arcade machines such as Donkey Kong and Punch-Out came with a Sanyo monitor which has a built-in audio amplifier. This amplifier constantly hums when the monitor is powered on, even when the game PCB isn't connected to it. Here's a short video that someone made demonstrating what's known as the "Nintendo hum":https://youtu.be/E7pupyO-VGoThe game boards themselves output a clean line-level audio signal; I've connected a Punch-Out board to a set of powered PC speakers, and there was no hum whatsover; perfectly clean audio.The Nintendo/Sanyo amplifier doesn't have much on it: just a few transistors, capacitors, and resistors:Replacing every component with brand new ones doesn't eliminate nor even reduce the hum.are some very high resolution schematics (8956 x 6228; if it's showing up small on your screen then your browser is automatically resizing it, or the site is only showing you a preview page) of the monitor and amplifier (the amplifier is in the lower left-hand corner). The amplifier gets its power through the monitor, so its circuitry is part of the equation.

author: BrianHG
author_rank: Super Contributor
timestamp: January 24, 2017, 06:57:37 pm
content: That good old 15khz and 60hz flyback interference....Try disconnecting the volume knob from the amp and place a volume control right at the amp to see if the hum remains the same level.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 24, 2017, 07:14:10 pm
content: Quote from: BrianHG on January 24, 2017, 06:57:37 pmThat would take some doing to rig something like that up. I may try it later. I'd have to pull a 50kOhms pot from a parts chassis.I know that it's possible to have an audio amplifier in close proximity to a ~15 kHz CRT without inducing hum, because most ~15 kHz CRT-based television sets didn't have any significant hum coming out of the speakers. The one I have in my living room is practically silent even if you put your ear right up against the speaker; the only thing you hear is a sound similar to the sound of a breath. If your ear isn't pressed directly against the speaker, you hear nothing at all. On the other hand, I can clearly hear the hum from my Punch-Out when sitting in my chair 15 feet away (Punch-Out has two monitors, and thus, two amplifiers, so the hum is louder than with e.g., Donkey Kong).QuoteI've already done that (or rather, the equivalent of that). As I said in my OP:"This amplifier constantly hums when the monitor is powered on, even when the game PCB isn't connected to it. The game boards themselves output a clean line-level audio signal; I've connected a Punch-Out board to a set of powered PC speakers, and there was no hum whatsover; perfectly clean audio."

author: BrianHG
author_rank: Super Contributor
timestamp: January 24, 2017, 07:18:21 pm
content: Yup, I notice and edited my reply.For the POT, just short pins JB1&2 and tie a 50Kohm resistor to pin 3. This will give you max volume, but just check if the hum is there.The adjustment module have some high voltage signals from the CRT control going right to the volume control as well. I'm checking if there is signal leakage coming through there.If this one doesn't work, then we need to look at filtering the power supply for the AMP board.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 24, 2017, 07:46:48 pm
content: Quote from: BrianHG on January 24, 2017, 07:18:21 pmWouldn't that giveminimumvolume? When the existing volume pot is turned "up" all the way for maximum volume (i.e., clockwise all the way) it is at a low resistance value: 11.5 ohms as measured in-circuit. When it is turned all the way "down", it measures 50.1 Kohms in-circuit.In any case, I have a couple of Sanyo parts chassis that I can easily pull the 50Kohm volume pot from anyway.

author: dmills
author_rank: Super Contributor
timestamp: January 24, 2017, 09:18:21 pm
content: Does it still hum if you unplug JB? I am suspicious of that earth connection between the volume and brightness pot on the control unit, it **might** be ok, but it is making my spider senses tingle.Urk! Am I reading this right? Looks to me on a quick glance that the whole thing (Including the audio, and by implication whatever supplies the audio to the thing) is LIVE CHASSIS. The monitor is no surprise, but I would have expected some isolation between it and the audio input doings? Power supply is top right.Regards, Dan.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 24, 2017, 09:20:38 pm
content: 3 words.. "pi section filter".PEACE===>T

author: DaJMasta
author_rank: Super Contributor
timestamp: January 24, 2017, 09:53:10 pm
content: Have you probed the amp (or its power rails) with a scope and have you tried shielding the amp board or the audio signal cables?I get the impression that it's either EM noise generated by the monitor driving circuitry or noise on the power rails generated by the very same. If it's present in the power rails going to the amp, you should be able to filter them out with some extra capacitance on the supply, inline ferrites on the DC lines, or similar. If it's radiated EMF inside the chassis, then you'd have to shield the parts - if the mount for the audio board is metal, it may not be the most likely culprit, and I'd first look towards swapping the audio signal lines with a shielded, twisted pair or similar.If the noise that isn't coming through the audio line (when the board is disconnected and not out of the speakers), that would be harder to fix, because it's probably some slight physical movement involved with the monitor's components.Also worth mentioning, that at least in the video, the primary sound component is 120Hz. I believe this is often what's referred to as the 60Hz hum, but it's actually the second harmonic, a 60Hz signal is quite low. I also don't hear the 15kHz signal in the video, at least, though that could also be related to frequency response of the mic. 15kHz is very high for human hearing, in the top octave of what pretty much anyone can hear, so if your high frequency hearing is good enough, it can be audible but it's a pretty distinct whine of a sound.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 24, 2017, 09:59:31 pm
content: Quote from: dmills on January 24, 2017, 09:18:21 pmYes, the monitor has a live chassis; nearly all old arcade monitors did. But there was always an isolation transormer installed in the cabinet between mains from the wall and mains input on the chassis. In the case of Nintendo cabinets, it was an especially big transformer which served as both a step-down transformer (120-to-100 VAC) and an isolation transformer, because the Nintendo/Sanyo (and Sharp in some cases) monitors were built to Japanese power standards (100 VAC). For all other arcade monitors destined for the U.S. market, such as the Electrohome G07, Wells-Gardner K4900, K7000, etc., they were designed for 120 VAC in the first place, so they only needed a small isolation transformer, like this -link.Some newer CRT arcade monitors, such as those made in the '00s (the final ones were made in the late '00s) didn't have a live chassis, so they didn't need an added isolation transformer.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 24, 2017, 10:25:48 pm
content: Quote from: DaJMasta on January 24, 2017, 09:53:10 pmI don't have an oscilloscope. The audio signal cables are already shielded:Plus, as I mentioned before, the amplifier hums in exactly the same way regardless of whether the game board is connected to it or not. Disconnecting the game board takes the audio signal completely out of the equation.I wouldn't know how to go about shielding the amplifier itself from radiated EMF.QuoteYeah, 60 Hz is considered "bass" (60 to 80 Hz is a typical crossover range between midrange drivers and subwoofers), and 15 kHz (which is actually more like 15.7 kHz for a standard resolution CRT display) is at or very close to the upper limit of human hearing for most adults. The stock Sanyo speakers that Nintendo installed couldn't reproduce ~15.7 kHz anyway. They are merely midrange drivers; there is no tweeter nor even a "whizzer cone". They also couldn't reproduce 60 Hz, at least not with any authority.

author: KE5FX
author_rank: Super Contributor
timestamp: January 24, 2017, 10:53:50 pm
content: That circuit is a dog's breakfast of ground loops. Try opening up the ground connection at the lower end of the volume control pot.

author: BrianHG
author_rank: Super Contributor
timestamp: January 24, 2017, 11:10:12 pm
content: Wouldn't it be funny if audio transformer T901 is just receiving the EM energy leaking from the Yoke and sending it to the speaker.Q: Did just simply disconnecting the volume control affect the hum?

author: DaJMasta
author_rank: Super Contributor
timestamp: January 24, 2017, 11:44:33 pm
content: Quote from: MaximRecoil on January 24, 2017, 10:25:48 pmIf it's the same as the video, at least, it's not exactly the same - the volume of it is considerably louder with the audio system powered up.Shielding the amp would be something like putting it in an aluminum box, any sort of metal housing could use as a temporary one to see if it would actually help (even like a pie tin could do enough to show you if it would help or now).Since the cables are shielded and much of the chassis is metal... I think the hunting for ground loops suggestion is probably a good one.If the speakers themselves are close to the monitor and look unshielded (you can see the coil), it could be worth sticking a grounded of sheet of metal between them and see if it reduces the noise (but be very careful to not touch the monitor tube).

author: dmills
author_rank: Super Contributor
timestamp: January 25, 2017, 12:10:07 am
content: Dogs breakfast it is right enough.Disconnecting the audio source and unplugging the volume control loom are NOT in fact the same thing because the ground connection to the volume control is cross connected to the ground on the brightness pot on the control assembly, it is this cross connection that I was wanting to isolate as a source of noise....You really, really need a 'scope, an old analogue 20MHz one is more then good enough for this sort of thing, and should only cost a few beer tokens at a hamfest.Regards, Dan.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 12:11:19 am
content: Quote from: DaJMasta on January 24, 2017, 11:44:33 pmIn that video, the guy disconnected the speaker from the amplifier so that just the faint monitor hum could be heard, which of course will eliminate the hum from the amplifier, because the speaker is where the hum is output/heard to begin with. I'm talking about disconnecting the game board, and thus, the audio input signal, from the amplifiers, but still leaving the speakers connected. The hum is exactly the same either way.Quote from: BrianHG on January 24, 2017, 11:10:12 pmDisconnecting the 3-position JB plug (the one that goes to the volume pot) reduced hum by a lot, but it didn't eliminate it. It removed the "buzzing" component of the hum, making it a lot quieter and a lot more tolerable. I haven't tried connecting a pot directly to the JB header pins yet. Doing so would eliminate that connection with the brightness pot though; does it need that for both the brightness and volume controls to work properly? If it doesn't need that, why is it there?

author: KE5FX
author_rank: Super Contributor
timestamp: January 25, 2017, 12:18:00 am
content: Quote from: MaximRecoil on January 25, 2017, 12:11:19 amIt's there because somebody in HR screwed up and hired an idiot when they needed an electrical engineer.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 12:23:11 am
content: Quote from: KE5FX on January 25, 2017, 12:18:00 amDo you think I should try connecting a volume pot directly to the JB header pins, thus eliminating that shared connection between the brightness and volume pots?

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 25, 2017, 12:31:07 am
content: How does it sound with the "AUDIO INPUT" pins all SHORTED together (grounded)?Practically ANY audio amplifier will pick up noise with a floating input acting as an antenna.How does it sound with that connection between "JB" and the control board removed?The audio volume pot appears to be adjacent to the video control pots, brightness, H-center, V-hold, V-size, etc.In fact, the ground end of the audio volume pot is actually connected over to the bottom of the brightness pot.I would certainly try disconnecting the bottom (ground) end of the volume pot from all the other connections (local ground, the bottom of the brightness pot, etc.) As others have mentioned, that is just asking for ground loops and other noise-collecting topologies. The bottom of the volume pot should be connected ONLY back to the audio amp board.But honestly, I would just dump that audio amp board in the old CRT monitor. You can get a shiny new replacement from Ebay, etc. for likely $5 with free shipping. And be completely clear of that antique display gadget.Is the old CRT technology part of the "vintage ethos" or something? I would seriously consider dumping the entire CRT display and replace it with a modern LCD. What they were showing on that video was physical vibration of the deflection yoke causing audible noise. 60/120Hz for the vertical sweep, and 15.75 KHz for the horizontal sweep. The noise is coming from the yoke coils themselves acting as inefficient "loudspeakers" and causing those sounds.It is quite possible that problem becomes worse with age. It is an artifact of rather cheap mass-produced deflection yokes. It may be possible to reduce or even eliminate the acoustic noise by carefully potting. Perhaps even with parafin. Although that might cause a fire hazard if it gets really hot.Of course "vertical" and "horizontal" are referenced to using the display in "landscape" mode. If the game console has the screen mounted in "portrait" mode, then you can exchange the names "vertical" and "horizontal".

author: BrianHG
author_rank: Super Contributor
timestamp: January 25, 2017, 12:43:11 am
content: Quote from: MaximRecoil on January 25, 2017, 12:23:11 amYes, place the volume pot right at the amp. Keep it away from any video signals.I dont think it's the brightness pot creating the problem, it's the shared grounding plate with the Vertical hold and V size since these can be very large voltage signals. Though, during the vertical blanking, the brightness might experience a 4-8v spike.

author: KE5FX
author_rank: Super Contributor
timestamp: January 25, 2017, 12:50:50 am
content: Quote from: MaximRecoil on January 25, 2017, 12:23:11 amIt might help if you just break the shared ground connection at the control panel. The ground return isn't as sensitive as the high-impedance signal line, but you still don't want to share it with NTSC video circuitry.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 01:24:05 am
content: Quote from: BrianHG on January 25, 2017, 12:43:11 amQuote from: KE5FX on January 25, 2017, 12:50:50 amOkay, I disconnected the JB plug from the amplifier and connected a 50K pot directly to the JB header pins. Everything worked fine, i.e., the brightness wasn't affected and the 50K pot controlled the volume correctly. However, the hum wasn't reduced by any noticeable amount.If I turn the volume down there is less hum, and if I turn it up the hum gets louder, but that happens with the normal volume control hooked up too, and is to be expected, because turning the pot changes the level of amplification of the hum. When I tried it earlier with the JB plug just plain disconnected, it had a quiet hum the same as if the volume pot was connected and turned down all the way.

author: xavier60
author_rank: Super Contributor
timestamp: January 25, 2017, 01:33:47 am
content: Does the buzz change in the way it sounds when the V-hold is misadjusted?

author: BrianHG
author_rank: Super Contributor
timestamp: January 25, 2017, 01:50:49 am
content: Quote from: MaximRecoil on January 25, 2017, 01:24:05 amOk, 1 last test, now with the short volume control, disconnect the line in on the amp coming from the digital board. If the hum disappears, a line level audio ground loop transformer will get rid of you hum. If the hum stays, you now just need to filter the power going into the amp. (If I read the schematic properly) 1 or 2 Diodes + 1 or 2 big caps to the power input will do.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 01:57:12 am
content: Quote from: Richard Crowley on January 25, 2017, 12:31:07 amI don't know. If I tried that and it eliminated or significantly reduced the hum, would that give any insight on how to eliminate the hum when everything is hooked up?QuoteI just tried those things; see my previous post for details.QuoteI already know that will work, because as I mentioned in my OP, I've connected the audio output of the game board to a set of powered PC speakers and the audio was perfectly clean; zero hum. However, I'd prefer to use either the original amplifier or a redesigned one which could mount and plug in the same as the original.QuoteThe old CRT is about the video looking good vs. the video looking bad. I hate digital displays in general with a passion, and multiply that hatred a hundredfold for digital displays used with ~240p video games. I don't even use a digital display with my PC. I have a 22" Mitsubishi Diamondtron CRT monitor which can sync to 1920 x 1440 @ 60 Hz, and it's beautiful, even though it's been in almost constant usage for about 12 years straight. But I would use a digital display with a PC or other device capable of outputting a resolution that matches the fixed resolution of a digital display, long before I'd use one with an old video game.I have enough CRTs in this house, including 3 fully-working spare Nintendo/Sanyo arcade monitors, and two parts chassis which I could fix if I needed to, that I'll never have to downgrade to an LCD in my lifetime. Plus, I'd never do it anyway; I'd rather hang an "out of order" sign on it and never play it again than put LCDs in there, which would do nothing but irritate me every time I played the game.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 02:10:50 am
content: Quote from: BrianHG on January 25, 2017, 01:50:49 amWith the line-in cable disconnected from the amp and the volume pot connected directly to the JB header pins, there is a quiet hum, the same level of quiet as when everything is connected and the volume pot is turned all the way down. However, turning the volume up doesn't make the hum get louder like it does when the line-in cable is connected.Also, with the line-in cable disconnected from the amp, if I touch one of the legs on the pot with my finger, it induces a loud hum (it does that on two of the three legs; touching the leg that originally was connected to the black wire has no effect). On the other hand, with the line-in cable connected to the amp, touching the legs of the volume pot with my finger has no effect, regardless of which leg I touch.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 25, 2017, 02:25:43 am
content: With all the audio wiring disconnected, isolated, or shorted, the hum that remains is most likely ripple in the power supply. You could likely fix that by adding a big additional power bus filter capacitor right on the audio board, in parallel with C378. I would even consider adding 500uF of 1000uF in there (if space permits?). And maybe even increase the capacitance at C392 and C378 (? the one next to R375). That would tame the power bus ripple.

author: dmills
author_rank: Super Contributor
timestamp: January 25, 2017, 02:36:04 am
content: Get thee to a car audio place, and pick up an audio line level ground loop isolator, there are usually a little plastic tube with a fairly shonky pair of audio transformers wired to phono plugs, but they work well enough for this sort of thing. Wire it into the audio line feeding the monitor and most of the hum will vanish, should cost about $10 or so.Much better things are available, but at a price.Replace the electrolytic caps on the amp board with some modern ones (Use 105 degree parts, CRT monitors are a hot environment) and you can probably get rid of most of the rest, at least one on there looks properly suspect to me.Regards, Dan.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 03:09:03 am
content: Quote from: dmills on January 25, 2017, 02:36:04 amThe amplifier in my picture is just a spare from a parts chassis that I've never used. I've replaced all of the electrolytic capacitors on both of the amps in my arcade machine, as well as the transistors. It had no effect on the hum; it never does. Many people have done it; they are even sold in convenient kits along with all of the electrolytic capacitors for the main chassis PCB (for example -https://www.arcadepartsandrepair.com/store/monitors/monitor-cap-kits/sanyo-20-z2aw-audio-board-cap-kit-105c-nichicon/) so you don't have to examine your PCB, write them all down, and trudge through Mouser or Digi-Key to get them.Allegedly,Mark Spaeth, a cantankerous MIT-educated electrical engineer, was working on a "Nintendo hum eliminator" at least as far back as 2009, but as far as anyone knows, nothing ever came of it.

author: dmills
author_rank: Super Contributor
timestamp: January 25, 2017, 03:42:57 am
content: The audio line isolating transformer will get you hum down to about the level you get with the volume turned all the way down, but with the volume up, do that and then we can look at the rest of the things problems.That amp looks like it was done by someone familiar with valves, 140V supply, output transformer!RC filter on the middle pin of JC seems like a likely fix for the residual to me, maybe 1K and 100uF 160V to ground?Regards, Dan.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 04:32:35 am
content: Quote from: dmills on January 25, 2017, 03:42:57 amYeah, a guy in a thread I made on this same topic about 5 years ago thought that was bizarre. At first he thought it was an easy job (I asked about designing a plug-n-play replacement amplifier that didn't hum), until I told him I was showing 135 VDC on my meter:"This really is a terrible design, I don't know what they were thinking when they came up with it. Having an input voltage of 135V makes it almost impossible to design a modern IC based replacement."The thread is locatedhereif you want to take a look at it. That's the thread which prompted one of the posters to make that video that I embedded in my OP. He was originally claiming that his Nintendo cabinet had no hum. I said:"Can you make a similar video with your hum-free machine? I'm a little skeptical that a Sanyo amp can be hum-free, but if yours really is, it would be quite remarkable ... and maybe someone can figure out why yours has no hum while everyone else's does."Then he discovered that his Nintendo machine has hum just like everyone else's does. Someone else in that thread did some tests with both an original Sanyo amp and areplacement sold by Mike's Arcadewhich has a completely different design and is powered off 12 VDC. Apparently that one hums too.Skimming back over that thread, it looks like "channelmanic" had some ideas that were the same or similar to some of the ideas on this thread, such as increasing certain capacitor values on the amp PCB, and ..."Has anyone tried a 1:1 audio transformer to see if it's a ground loop issue?""Between the board and the amp...You need a 1:1 audio isolation transformer. "Isn't that what you're saying to do with the "audio line isolating transformer"?

author: BrianHG
author_rank: Super Contributor
timestamp: January 25, 2017, 05:45:10 am
content: Just so we are clear, are you looking to cheaply patch your existing amp board with caps and potentially a line isolation transformer?Or, would you prefer putting in a cheap 15watt 12v audio replacement amp, which will probably end up costing you the same amount of money?Something like this:https://www.aliexpress.com/store/product/Small-Digital-Audio-Motorcycle-Stereo-Amplifier-Ampli-Kit-15W-15W-Dual-Channel-Power-Amp-12-Volt/906697_1737339596.htmlOr this:https://www.aliexpress.com/store/product/For-TDA2050-Power-Amplifier-Board-Single-Power-Supply-Mono-DC-9V-35V/1829717_32776811171.htmlOr this:https://www.aliexpress.com/store/product/5-pcs-Free-Shipping-6-12V-Single-Power-Supply-Audio-Amplifier-Board-Module-TDA2030A-Module/1089303_32449669807.html

author: xavier60
author_rank: Super Contributor
timestamp: January 25, 2017, 05:55:50 am
content: If the hum is getting in via the supply rail, try putting a 100 ohm resistor in series.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 25, 2017, 06:04:01 am
content: Apparently they LIKE the old, lousy (by modern standards) low-rez CRT video, but they DON'T like the accompanying vintage audio with hum in the background. Go figure.It looks like a first-generation IC design back in the vintage CRT days. And, of course it is a transformerless "hot-chassis" design, PLUS they still need all those high voltages to drive the CRT. So operating the audio amp on 140V should come as little surprise.I have to agree with @BrianHG about just dumping it and getting a nice drop-in replacement amp module. Trying to redesign a silk purse out of that old sow's ear is just the treadmill to insanity. Cut the losses and get on with your life.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 06:07:51 am
content: Quote from: BrianHG on January 25, 2017, 05:45:10 amI'd rather eliminate or greatly reduce the hum from the original amplifiers. As a bonus, if a solution were found, it could potentially help a lot of Nintendo machine owners, who are generally unwilling to deviate very far from original equipment.I've always been aware of the option to use a completely different amplifier design which won't mount in the original location or accept the original plugs. As I said in my OP, I've done it before as a test using a set of powered PC speakers about a dozen years ago, and the audio was perfect; no hum. The PC speakers weren't even in the cabinet though; they were in the next room (I ran a long pair of RCA cables to them), so I don't know how it would work out if the PC speakers' amplifier were mounted near the monitor.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: January 25, 2017, 06:36:24 am
content: Quote from: Richard Crowley on January 25, 2017, 06:04:01 amThat's because a dialed-in CRT fed by a pure RGB video signal is a beautiful thing, while a buzzing audio hum isn't. And there's nothing vintage about hum; it's a design flaw. My bone-stock Atari Missile Command arcade machine from 1980 (4 years older than my Nintendo Super Punch-Out machine) has no hum whatsoever.And you have it backwards. Modern standards for displaying "moving pictures" are a step down from the old standards. A 70mm IMAX-format film projector or a Barco 909 CRT video projector blows any digital display technology out of the water. Digital displays are cheap to manufacture, compact, and energy-efficient; those are their advantages. Of course, none of those things have anything to do with how the picture actually looks.QuoteIt comes as a surprise because Nintendo is the only company who ever did such a thing. An audio amplifier integrated with the monitor is unheard of in the arcade world, aside from Nintendo/Sanyo monitors (and the less common Nintendo/Sharp monitors). Wells-Gardner, Amplifone, Electrohome, Hantarex, etc.; none of them had audio amplifiers; they were just pure monitors. Everyone else integrated the amplifier into the game board or put it on a board mounted right next to the game board (such as with the Atari AR and ARII boards). That's why it's called "Nintendo hum" and not "vintage arcade machine hum".And that's not the only "not invented here" thing Nintendo did. Their monitors also inverted the colors of the video signal, so that if you hooked up any game board other than a Nintendo one, all the colors would be inverted. The Nintendo game boards inverted the colors (so if you hook one up to an ordinary arcade monitor, all of the colors are inverted), which got inverted again back to normal colors by the Nintendo monitor. And they didn't stop with the monitors; practically everything about a Nintendo arcade machine is non-standard: non-standard button diameter, non-standard joystick mounting hole spacing, non-standard carriage bolts, non-standard power (100 VAC combined with a 120-to-100 VAC step-down transformer), non-standard marquee light, and non-standard wood thickness which results in a non-standard T-molding width.

author: martinator
author_rank: Contributor
timestamp: January 25, 2017, 06:46:54 am
content: Sounds like the old Vectrex buzz issuehttp://int03.co.uk/blog/2016/02/06/vectrex-buzz-fix-enjoy-the-silence/

author: tooki
author_rank: Super Contributor
timestamp: February 07, 2017, 01:17:43 pm
content: Quote from: MaximRecoil on January 25, 2017, 06:36:24 am100V is the standard mains voltage in Japan. A number of game machines were built around their home country's mains voltage, and simply equipped with step-up/down transformers for foreign markets.

author: MaximRecoil
author_rank: Regular Contributor
timestamp: February 07, 2017, 07:19:20 pm
content: Quote from: tooki on February 07, 2017, 01:17:43 pmYes, I know.QuoteWith regard to arcade machines intended for use in the United States, as far as I know, only Nintendo did that. If you know of any others, please name them.There were a lot of Japanese companies in the arcade game business, e.g., Taito, Technos, Konami, Namco, Data East, Sega, SNK, Irem, and you won't find that non-standard stuff in any of them that I've ever heard of. In many, if not most, cases, those companies licensed their arcade games to American companies, who manufactured the cabinets for the US market. For example, Namco licenced Pac-Man, Galaxian, Galaga, and others to Midway, and they licensed e.g., Pole Position and Dig Dug to Atari. Taito licensed Space Invaders to Midway. Irem licensed Moon Patrol to Williams. SNK licensed Ikari Warriors to Tradewest, who in turn contracted with arcade cabinet specialist Dynamo to build the cabinets. That's not even close to an exhaustive list. It made more sense to them to let an American company build the ~300-lb. cabinets for the U.S. market than to build them in Japan and ship them over here.In the case of Nintendo, most of their classic arcade machines were built in Japan and shipped here. However, Nintendo of America built some of them here in the U.S., yet they still had all of the non-standard stuff that the Japanese-built Nintendo cabinets had. I, and many others, believe that this was Nintendo's attempt to corner the replacement parts market for their machines, especially the monitors, which, aside from the game board, was the most expensive part in the cabinet. Not only did the monitors require 100 VAC even though it's entirely possible to build a monitor that will run on a range of 100 - 120 VAC (the Happ Vision Pro will, for example), but they inverted the colors of whatever video signal they were fed, which inverted the inverted video signal from Nintendo game boards back to normal colors. There is no practical reason for doing that; it just makes their monitors incompatible with other companies' game boards, and their game boards incompatible with other companies' monitors. Their monitors having a built-in audio amplifier added to the incompatibility. For example, if you wanted to replace the monitor in your, e.g., Donkey Kong machine with anything other than a Nintendo/Sanyo or Nintendo/Sharp monitor, not only would you have to devise a way to invert the inverted colors back to normal, but you'd have to come up with an audio amplifier for it as well.