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 Post subject: Notes on adding an AC adapter to a Super Scope
PostPosted: Fri Mar 09, 2018 4:23 am 



Joined: 03 Mar 2005
Posts: 315
I have a lot of fond memories of the Super Scope, and when I picked one up recently, I thought I'd try and tackle its infamous battery-eating problem by modding in an AC adapter. While I'm not the first person to do this, a lot of the other mods I've read about seem to do nothing more than disconnect the +/- wires from the Super Scope's battery connectors and tie them to the +/- wires of an AC adapter, and this can seemingly cause problems.

In my case, with only this much, I saw my shots drift further and further away from where I was shooting over the course of a few minutes until I paused and did another calibration. It was much worse than I'd ever seen when using batteries. I've recently fixed this by doing things a little more properly, and I thought I'd share what I learned. If anyone reading this ever wants to wire in their own AC adapter, it's extremely simple, but there are definitely a few points you should know.


1. While six AA batteries provide the Super Scope with 9V of power, there is actually a small 78L05 linear regulator on the main PCB, and it appears that everything else runs on the 5V it outputs. You could probably get away with providing as few as 7V to the regulator, and since the power draw is low, I bet you'd be fine with up to 12V. I'd be wary of using an adapter rated any higher than that, though, and this is because...

2. AC adapters often output much higher voltages than they're rated for if the current draw is low enough. Definitely check any adapter you're going to use with a multi-meter. The adapter I'm using says 9V on the case, but if I measure it under no load, it says 13V. With the Super Scope on, it's 12V. Now, maybe the draw is so low that you could put 35V on the 78L05 and it would still never overheat, but for peace of mind, I wouldn't.

3. While battery-sourced voltage tends to be stable in the short-term, raw AC adapter output is often very messy. There can be voltage fluctuations with changes in current flow as well as large amounts of other noise at varying frequencies. If you do nothing else while modding in an adapter, I strongly recommend adding a ceramic decoupling capacitor that's at least 1uf somewhere right before the 78L05. Note that there is a 47nf ceramic decoupler there already.

4. What I initially did was put a 9V regulator between my AC adapter and the Super Scope PCB, but this was still giving me the shot-drift problem. With an oscilloscope, I was able to see that whenever I pressed the fire button under this arrangement, there would be a lengthy ~700mv p-p noise-period on the 9V line. I've since learned that linear regulators really, really like to have decoupling capacitors on their inputs, especially when the power source is physically far away and/or unstable. Some datasheets use the word "required". If you go the route of including a 9V regulator, then be sure to put at least a 330nf ceramic decoupling cap right at the base of the regulator itself, per the datasheet. I used 1uf because I had a bunch of those handy, and I also put one before the 78L05.

If you use a 9V regulator, make sure your adapter's real voltage output is at least 11V. An 8V regulator and 10V adapter would be fine as well.

5. While you're doing all of this, you might as well recap the Super Scope itself. There are four electrolytic caps on the main board, all of which you can replace with standard-sized 5x11mm caps if you get creative with positioning. The values are: 50V 1uf, 6.3V 47uf x2, 6.3V 100uf. Right at the tip of the gun is a big fat 6.3V 2200uf cap. Note that you can get away with replacing this with something taller, but not any fatter. Not unless you're willing to cut away plastic.

In the receiver that plugs into the SNES are one 50V 0.47uf cap and one 6.3V 47uf cap, if you want to replace those, too. There are also two unpopulated solder pads for 47nf decoupling caps; I added in 100nf because again, that's what I had. It works fine.

6. I drew up a little before/after diagram of what I did:

Image

The non-polarized caps are all ceramic. The values are not necessarily important; I used leftovers that I had handy. I did, however, decide to upgrade the 100uf cap after the 78L05 to 220uf. The 16V 56uf cap may be totally redundant, but I don't know when the heck else I'm going to use these, so why not?

With this, when I press the fire button, the noise on the 9V line is a mere 20mV p-p, and my shots no longer drift.


tl;dr - It's a good idea to add a linear regulator and a whole bunch of decoupling capacitors to a Super Scope AC adapter mod, because otherwise there will be electrical noise that causes problems like shot-drift.


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Fri Mar 09, 2018 10:59 am 


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Joined: 11 May 2015
Posts: 658
Location: America
awesome project, the battery drain and replacement cost was one of the reasons I didn't spend much time with the Super Scope. but I did love the pack in game as a kid. (still have some of the music stuck in my head :lol: ).


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sat Mar 10, 2018 2:08 am 



Joined: 03 Mar 2005
Posts: 315
Blair wrote:
awesome project, the battery drain and replacement cost was one of the reasons I didn't spend much time with the Super Scope. but I did love the pack in game as a kid. (still have some of the music stuck in my head :lol: ).


Super Scope 6 has a few tracks that are surprisingly awesome, like these:

https://youtu.be/ro-Fz3TchCA
https://youtu.be/4TNDobfirYU

The best Super Scope game IMHO is Metal Combat: Falcon's Revenge. The sprite animations and backgrounds are rich and high-quality, the action is hectic and fun (there is a co-processor in the cart), and the gameplay is quite deep and has decent replay value for a light-gun game. It's also amazing that it was only ever released overseas because the Super Scope wasn't popular enough in Japan, even though the game was made there.


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sat Mar 10, 2018 9:00 pm 



Joined: 14 Feb 2005
Posts: 467
Location: Los Angeles, CA
Love work like this, although I personally probably won't spend more time with the Super Scope.

I wonder - on a slightly less ambitious note - how well modern batteries like Eneloops mitigate the replacement issue?


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sat Mar 10, 2018 9:08 pm 



Joined: 19 Jul 2017
Posts: 573
As an easier fit for those who don't want to mod, would it make sense to design and 3D-print an equivalent of the Virtual Boy's AC tap for the Super Scope? Both normally use 6 AAs, and the Virtual Boy's AC tap allows it to directly use an SNES power supply.

I'm imagining something that sides into the battery compartment and clips in where the battery cover normally clips in, then that has a flap that opens to reveal an SNES-sized power port. Plug in an SNES (Or SNES-compatible) power supply, close the flap, turn it on.


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sun Mar 11, 2018 2:08 am 



Joined: 03 Mar 2005
Posts: 315
bigbadboaz wrote:
Love work like this, although I personally probably won't spend more time with the Super Scope.

I wonder - on a slightly less ambitious note - how well modern batteries like Eneloops mitigate the replacement issue?


Here is a guy who went all-out with the battery approach:

http://ioxor.com/?page_id=27

nmalinoski wrote:
As an easier fit for those who don't want to mod, would it make sense to design and 3D-print an equivalent of the Virtual Boy's AC tap for the Super Scope? Both normally use 6 AAs, and the Virtual Boy's AC tap allows it to directly use an SNES power supply.

I'm imagining something that sides into the battery compartment and clips in where the battery cover normally clips in, then that has a flap that opens to reveal an SNES-sized power port. Plug in an SNES (Or SNES-compatible) power supply, close the flap, turn it on.


That would be very cool. I'd be curious to look at the Virtual Boy PCB to see if it's got more in the way of decoupling before whatever voltage regulator must be in there. My solution for the Super Scope might have been overkill, but I do think you need something in the way of better decoupling than it comes with.

I wish I had taken pictures before closing everything up, but adding an AC adapter to a Super Scope really is the world's easiest mod. There are two long wires that run between the PCB and the battery case, one red (+) and one black (-), and disconnecting them from the battery case is practically impossible to screw up. Getting extra components in there is slightly difficult, but even an absolute beginner could pull it off with a minimum of effort and thought. The PCB is also single-sided with large solder pads, which is very beginner-friendly.

I did put a female port into the mod so I could disconnect the adapter, but the way the wire hangs out the back is kind of sloppy-looking. Not that it matters much to me when I'm playing. :wink:


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sun Mar 11, 2018 2:45 am 



Joined: 14 Feb 2005
Posts: 467
Location: Los Angeles, CA
SamIAm wrote:


Despite the NiMH/alkaline thing, Eneloops seem to replace standard AAs just fine in most gaming products. Do they really flat-out not power the Super Scope?


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 Post subject: Re: Notes on adding an AC adapter to a Super Scope
PostPosted: Sun Mar 11, 2018 3:15 am 



Joined: 03 Mar 2005
Posts: 315
bigbadboaz wrote:
Despite the NiMH/alkaline thing, Eneloops seem to replace standard AAs just fine in most gaming products. Do they really flat-out not power the Super Scope?


I don't know much about those batteries, but if they're 1.2V only when fully charged and less shortly afterward, they would quickly drop below the minimum 7V that you want for the 78L05. 6x1.2=7.2, 6x1.1=6.6.

EDIT: I wonder if that guy actually tried Eneloops or just assumed that they would be too low powered. Googling their voltage curve, it looks like they stay pretty flat around 1.2V until they're very close to being fully discharged. Anyway, it would still be riding the line.

Probably part of the reason why the Super Scope eats up standard alkaline 1.5V AAs so quickly is that those will often drop below 1.2V when they're still only about half used-up. Ironically, the 78L05 linear regulator winds up wasting large amounts of power when the batteries are fresh and combine to the full 9V, too. If you yanked out that regulator and replaced it with something like this, you could probably get way more out of any battery solution.


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